Abstracts from the 22nd Pupil Colloquium

Point Clear, Alabama

September 2 - 6, 1997.

Center for Visual Science1, University of Rochester, Rochester, NY
Applied Vision Research Centre2, City University, London, UK

Comparison Of Pupil Response Latencies & Reaction Times To Colour, Structure, Light Flux & Motion

Response latencies associated with the processing of light flux increments, stimulus structure, colour and coherent motion have been studied using manual reaction times and pupil responses. Our aim was to investigate latency differences between subcortical and central components of the pupil response and the correlation with manual reaction times measured for the same stimuli. For each of the four stimulus attributes investigated we observed an asymptotic decrease in reaction time with stimulus strength. This relationship was described well by a model with three parameters. The initial amplitude, the rate of exponential decay and the asymptotic reaction time expected as the stimulus strength approached infinity. A comparison of the shortest reaction times computed in this way reveals significant differences. The shortest reaction time was 184 ms and was obtained for a light flux increment. Averaged data for 4 subjects show increasing latencies for each of the other stimulus attributes: ~ 6 ms for grating stimuli, ~ 19 ms for colour and ~ 33 ms for coherent motion. In contrast, pupil responses to colour and grating showed no significant difference in latency, but both were ~ 40 ms longer than the ~ 240 ms measured for the pupil light reflex response. The latter response is mediated primarily by a subcortical projection. The greater pupil latencies for colour and grating are likely to reflect the processing of signals in the geniculostriate pathway, and in particular the analysis of pattern and colour information in V1. Differences among manual reaction times, on the other hand, are more likely to reflect time delays associated with the processing of different stimulus attributes and the analysis of stimulus specific information in extrastriate visual areas.

VSRC 1 , University of Alabama at Birmingham, AL 35294, USA.
Applied Vision Research Centre2 , City University, London UK.

Pupil Responses To Stimulus Colour, Structure And Light Flux Increments In The Rhesus Monkey

Visual stimuli that isolate pupil colour and pupil grating responses in human vision have been used to investigate the properties of stimulus-specific pupil responses in the rhesus monkey. The purpose of the study was to investigate stimulus- specific, pupil responses in the rhesus monkey and to compare response latency differences with human data. Pupil responses to light flux increments, isoluminant chromatic stimuli, and gratings of equal and lower space-averaged luminance were measured in two alert rhesus monkeys. The parameters investigated were luminance contrast and chromatic saturation. A reward was administered at the end of each measurement provided the monkey maintained accurate fixation throughout the trial. The stimuli were interleaved randomly and each response obtained by averaging 16 to 48 traces. The effect of flash luminance, grating contrast and chromatic saturation and hue were investigated. Both monkeys demonstrated pupil colour and grating responses similar to those observed in human vision. The results demonstrate clearly the existence of pupil colour, pupil grating and pupil light reflex responses in the rhesus monkey. The observed response amplitudes do not correlate with computed rod-contrasts for the same stimuli. Comparison of pupil colour and pupil grating responses of equivalent amplitude reveals similar onset response latencies. Both are however approximately 40 ms longer than the corresponding pupil light reflex latency. In general these pupil responses are qualitatively similar to those observed in humans. Pupil onset response latencies in the rhesus are however some 80 to I00 ms shorter and the pupil also shows more rapid recovery from constriction. The colour, grating and light flux components of the pupil response and their latency differences are similar in humans and rhesus monkeys.

Applied Vision Research Centre1, Northampton Sq., City University, London.
Neuroimaging Research Group2, Institute of Psychiatry, London.
Department of Experimental Psychology3, University of Oxford, Oxford, UK.

Processing Of Colour Signals In The Absence Of A Geniculostriate Projection

The purpose of this study was to investigate the residual processing of chromatic signals in a subject with unilateral damage to the primary visual cortex. Of particular interest was to establish the correlation between the subject's ability to make use of chromatic signals in the blind hemifield, to discriminate between different coloured targets, the corresponding residual pupil colour responses (PCRS) and the level and location of cortical activation generated by the same stimuli as revealed by functional magnetic resonance imaging (fMRl). The stimuli were designed to ensure that the subject was unable to make use of luminance contrast signals, particularly rod generated signals at the onset of the coloured stimulus. Psychophysical and pupillometric techniques were applied to obtain the discrimination scores and the corresponding PCRs for selected coloured targets. Stimulus induced changes in the pattern of neural activity when viewing such stimuli were assessed using fMRI. Pupil responses measured to predominantly long- (red), middle- (green) and short-wavelength (blue) stimuli showed that significant PCRs can be elicited by large chromatic stimuli when presented in the subject's blind hemifield. These responses were largest for red and absent for green and blue stimuli. Psychophysical data showed well above chance discrimination for red but not for green or blue stimuli. fMRI also reveals more active clusters for red than for green stimuli. The results obtained using the three different experimental approaches are consistent and suggest that retrograde degeneration of thalamic and retinal chromatic processing mechanisms caused by damage to the primary visual cortex in man does not abolish completely the ability to process chromatic signals particularly when large, long-wavelength stimuli are employed.

Oliver Bergamin, Andreas Sch|tzau, Stephanie Turtschi, and Mario Zulauf
University Eye Clinic, Basel, Switzerland

Age, Gender, and Test Location in Pupil Perimetry

Purpose. To evaluate the effect of age and gender on visual-field eccentricity in healthy volunteers. Methods. Pupil perimetry was performed on 100 healthy volunteers with a modified Octopus 1-2-3. Stimulus parameters were Goldmann size V, intensity 1632 cd/m2, duration 200 ms, background illumination 0 cd/m2, and interstimulus interval 3 s. Pupillometric parameters were velocity of contraction, redilation velocity, latency, duration of contraction, implicit time, pupillary diameter before (=PD at maximum) and after contraction, and amplitude. Age, gender, test location, and PD at maximum as covariate, and pupillometric parameters were investigated by analysis of variance. Results. No three-way interaction was found among the independent variables. No two-way interactions were observed with variable test location. An age/gender interaction was observed on all investigated parameters, i.e., the age effect was more pronounced in males than in females. All pupillometric parameters showed the significant main effect for test location to be strongest for duration of contraction (F=27.41) and for amplitude (F=22.77), weaker for implicit time (F=15.33) and for velocity of contraction (F=13.01), and minimal for latency time (F=4.784), and redilation velocity (F=4.371). Latency increased, amplitude, velocity of contraction, duration of contraction, and redilation velocity decreased with eccentricity. Conclusions. Areas closer to the center have the greatest pupillomotor response. Our results revealed that this holds especially for the pupillary contraction amplitude and duration, but less for latency time. Age effect is more important than gender in terms of pupil size and latency, but similar in amplitude.

Robert J. Clarke, Paul D. R. Gamlin
Department of Physiological Optics, University of Alabama at Birmingham, 924 South 18th St., Birmingham AL 35294.

Pupillary Response in Experimentally Induced Retinal Ischemia in the Rat.

The pupillary light reflex (PLR) is used clinically to diagnose diseases of the retina and visual pathways. Deficits in the PLR have also been proposed as a tool for the early detection of the onset of retinal diseases. However, there are few quantitative studies correlating pupillary function with retinal damage to support this hypothesis. We have therefore investigated the effects on the PLR of retinal injury elicited by a transient ischemic episode produced experimentally in one eye of hooded rats by raising intraocular pressure to 110mm Hg for 50-100 minutes. Visual stimuli were presented in the experimental eye before and after retinal ischemia, and pupil responses were recorded in the opposite eye, i.e. consensual pupillary reflex. Changes in pupil diameter were measured in the dark under infra-red illumination using an IR-sensitive video pupillometer. Five rats were used in this study. Normally the pupil had a resting diameter of approximately 3 mm and constricted approximately 1mm for the 2-4 log unit range of increased illuminances that were used in these experiments. Following retinal ischemia, a strong steady-state miosis was observed in some animals (resting diameter approximately 1.5 mm) for 24-48 hours, and the PLR was relatively unresponsive. Thereafter, the PLR partially recovered. Ten days following retinal ischemia, the PLR in three rats remained significantly reduced while in the other two it had recovered completely. In addition to whole-field stimulation, pupil responses were also studied using 10o or 20o spots positioned at different points within a 80o by 80o field. Constriction amplitude and mean pupil diameter were measured during a steady light presentation of 5 seconds. The largest responses were elicited in the lower nasal field, the smallest in the upper temporal field. Immediately following retinal ischemia pupillary responses were essentially absent in all animals. Ten days later, response amplitudes remained diminished throughout the visual field in 3 rats, but had returned to normal in 2 rats. The retinae were flat mounted and Nissl-stained and prepared for cell density counting. The ganglion cells were counted in the upper temporal retina close to the horizontal meridian. No difference was observed between ganglion cell densities in the control and experimental eyes of rats in which the PLR had completely recovered. As many as half the ganglion cells had been eliminated in the experimental eyes of those 3 rats in which long-term pupillary deficits were observed. In conclusion, these experiments show that the PLR is a sensitive method for tracking the time course and extent of the retinal effects of an ischemic ocular episode. Furthermore, the pupil may serve as an index of the functional integrity of retinal ganglion cells. This finding has potential implications for detecting diseases such as glaucoma.

VSRC1 , University of Alabama at Birmingham, AL 35294, USA.
Applied Vision Research Centre2 , City University, London UK.

Pupil Responses To Stimulus Colour, Structure And Light Flux Increments In The Rhesus Monkey

Visual stimuli that isolate pupil colour and pupil grating responses in human vision have been used to investigate the properties of stimulus-specific pupil responses in the rhesus monkey. The purpose of the study was to investigate stimulus- specific, pupil responses in the rhesus monkey and to compare response latency differences with human data. Pupil responses to light flux increments, isoluminant chromatic stimuli, and gratings of equal and lower space-averaged luminance were measured in two alert rhesus monkeys. The parameters investigated were luminance contrast and chromatic saturation. A reward was administered at the end of each measurement provided the monkey maintained accurate fixation throughout the trial. The stimuli were interleaved randomly and each response obtained by averaging 16 to 48 traces. The effect of flash luminance, grating contrast and chromatic saturation and hue were investigated. Both monkeys demonstrated pupil colour and grating responses similar to those observed in human vision. The results demonstrate clearly the existence of pupil colour, pupil grating and pupil light reflex responses in the rhesus monkey. The observed response amplitudes do not correlate with computed rod-contrasts for the same stimuli. Comparison of pupil colour and pupil grating responses of equivalent amplitude reveals similar onset response latencies. Both are however approximately 40 ms longer than the corresponding pupil light reflex latency. In general these pupil responses are qualitatively similar to those observed in humans. Pupil onset response latencies in the rhesus are however some 80 to I00 ms shorter and the pupil also shows more rapid recovery from constriction. The colour, grating and light flux components of the pupil response and their latency differences are similar in humans and rhesus monkeys.

Grünberger J., Linzmayer L., Lesch O.M., Walter H., Stöhr U., Grünberger M., and Zyhlarz G.
University Hospital of Psychiatry Vienna, Waehringer Gürtel 18-20, A - 1090 Vienna

Psychophysiological Diagnoses of Alcoholics: Fourier Analysis of Pupillary Oscillations and Receptor Control for Determination of Deficit of Acetylcholin

Alcoholics exhibit memory deficits which are related to a reduction of acetylcholine. Furthermore in these patients a central nervous deactivation has to be assumed. Therefore we analyzed pupillary oscillations during the recording period of 25,6 sec. Using Fourier analysis the spectrum was divided into five frequency bands (0,0-0,2; 0,21-0,4; 0,41-0,6; 0,61-0,8; 0,81-1,0 Hz). We were also interested in the power (sum of the frequency bands: 0,0 - 1,0 Hz). After application of a 0,01% tropicamide solution the receptors of the pupil were blocked and a pupillary dilation could be observed. We assume the more severe the deterioration the wider the dilation which differs significantly from those of healthy normals. 44 alcoholics with an age between 40-55 years were compared' with 18 healthy controls similar in age. The patients were diagnosed according DSM-III_R as severe alcoholics (>7 symptoms). They were abstinent at least for 3 weeks, which was objectivated by means of CDR. The pupillary diameter (left eye) of the alcoholics and of normal controls was measured 8 times. At the measurement time points the central nervous activation and the activation during a calculation test (3rd and 108th min.) was measured by means of Fourier analysis of pupillary oscillations and pupillary dilatation after topical instillation of torpicamid was determined. Regarding basic activation as measured by Fourier analysis (power) significant differences between alcoholics and healthy controls could be found in baseline, in the 3rd, 20th, and 40th min. (P<0.01) as well as in the 60th, 80th, 100th, and 103rd min. (P<0.05). After a cognitive task (simple calculations) a difference between alcoholics and healthy controls was obtained in the 3rd minute. Summing up these results we found in alcoholics lower basic activation (lower amplitudes) and a decreased capacity for cognitive activation. The pupillary dilatation of 22% in alcoholics and 14% in normals controls (p<0.05) after instillation of tropicamide was parallel to the deterioration of memory functions which is caused by deficit of acetylcholin and possibly influenced by glutamate.

Peter Alan Howarth
Visual Ergonomics Research Group, Department of Human Sciences, Loughborough University Leicestershire, LE11 3TU England

Can Pupil Responses be used to Reveal Emotions?

The iris muscles are under the direct control of the autonomic nervous system. Light is not the only stimulus which elicits iris responses, and changes in pupil size accompany changes in emotional state. It has been claimed in the past that the pupil constricts when an unpleasant scene is viewed, and dilates when the person's response to a picture is positive. In particular, Barlow (1969, 1970) claimed that pupil size changes correlated to subjective ratings of 'pleasantness', with a bi- directional response. However, this claim is disputed, and many authors believe that dilation is the only response elicited by emotional changes. Previous studies have received plentiful criticism, in particular because of flawed experimental methods. To examine whether pupil responses can reveal emotions, a new technique was devised. Twenty-two subjects viewed a series of twelve slides. Each of the slides was presented twice, once in-focus and once out-of-focus (and rotated). Each slide was preceded by a grey slide, and the order of slide presentation was randomized. Pupil size was monitored continuously, and the metric subsequently used was the difference between the changes in size in response to the in-focus and the out-of-focus slide. Once the pupil changes were recorded, subjects were shown the slides once more, and asked to rate them on a number of emotional scales (e.g. like/dislike, unpleasant/pleasant). Most of the 262 responses were dilations. Surprisingly, the correlation with the subjective responses on all of the emotional scales was poor. However, this result can be explained by considering that one slide could be judged pleasant and exciting, another could be judged unpleasant and exciting, and a third could be judged very pleasant but unexciting. Each of these slides could arouse the person, leading to a pupil dilation, but neither emotion would be correlated with the pupil response. In conclusion, pupil dilation was seen in response to viewing slides of differing content, but these changes could not be said to be associated with any specific emotion.

Randy H. Kardon M.D. Ph.D., Darwin B. Wooten M.D.
University of Iowa and Veterans Administration Hospital, Department of Ophthalmology, Neuro-ophthalmology Division, Iowa City, Iowa.

Effect of Visual Field Loss on the Waveform of the Pupillary Light Reflex

Purpose: Pupillary reactions during a continuous five second light stimulus consist of both a phasic and a tonic component which can be demonstrated as a waveform by plotting pupil size over time. The aim of this study was to compare the pupil waveforms of a damaged eye in response to varying intensities of light to waveforms of the normal fellow eye. This was done to better understand what components of the waveform are affected by damage and what to look for during clinical observation. Methods: Forty-five patients with an RAPD and visual field loss were tested by computerized pupillography. Each eye was stimulated with a light that was on for five seconds and off for five seconds. Seven different light intensities were used at 0.5 log unit increments over a 3 log unit range. A new technique of signal analysis was developed to analyze the waveform of the pupil responses to the light stimuli and to estimate the relative afferent pupillary defect (RAPD) using the phasic (initial constriction) and tonic (escape) portions of the response. Results: In some eyes the damage showed a greater effect on the phasic portion of the response and in some eyes the tonic portion of the waveform was more affected. We are currently trying to determine what is the clinical relevance of decrease in amplitude of selective portions of the waveform and whether this is related to the location of field loss, the etiology of damage, or the extent of damage. Conclusions: Preliminary results indicate that loss of the central visual field may cause more effect on the tonic portion of the pupil response to a constant light than the phasic portion. The clinical implication is that the degree of "pupillary escape" in relation to the amount of initial constriction may be related to what portion of the visual field has been damage

Merlin D. Larson, MD and Pekka Talke, MD
Department of Anesthesia, University of California, San Francisco

Effect of alfentanil and dexmetetomidine on the human pupillary light reflex

Introduction: Much of our understanding of the pharmacological properties of the human pupillary light reflex have been extrapolated from animal data. Because of species differences, many drug responses observed in animals may not pertain to human clinical observations. We studied the effect of alfentanil (a pure mu opioid agonist) and dexmetetomidine (an alpha 2 agonist, similar to clonidine) on the human pupillary light reflex during the stable miosis of low dose general anesthesia. Methods: Thirteen human volunteers were anesthetized with stable concentrations of either propofol (100 mcg/kg/min, n=7) or isoflurane 0.8% (n=6). After at least 15 min of stable recordings, the following drugs were administered using computerized infusions to target precise plasma concentrations: alfentanil (25, 50 and 100 ng/cc) and dexmetetomidine (0.6 ng/cc). Pupil size and light reflex were measured with an infrared portable pupillometer (Fairville Medical Optics, Inc.). Noxious stimulation was provided by a 5 sec, 60 mamp electric current applied via needle electrodes placed below the skin. Results: Alfentanil had no effect on pupillary size or the light reflex at any concentration. Dexmetetomidine increased the light reflex 23 ± 16% (P < .002) without changing pupil size. Both drugs depressed reflex dilation of the pupil (P < .05). Discussion: The pharmacologic properties of the human pupillary light reflex are unlike those of most experimental animals. Opioids, for example, depress the light reflex in dogs and cats but have no effect in humans unless the mechanical properties of the iris are altered by miosis. Alpha 2 agonists, on the other hand, dilate the pupils of cats and rats, but produce constriction in humans. Our finding that the light reflex is increased by dexmetetomidine in anesthetized humans might be explained by a depressant action of the drug on norepinephrine containing neurons in the lower brainstem.

A. Lyubarsky, M. Pennisi and E.N. Pugh, Jr.
Departments of Psychology and Ophthalmology, Univ. of Pennsylvania High

Sensitivity Of Mouse Pupil To Light

Purpose: To measure the pupil size of mice, and determine the dependence of the pupil area on retinal illumination. Methods: Anesthetized C57B/6 mice of age 7-8 weeks were placed in a ganzfeld in darkness, and illuminated with monochromatic 500 nm light whose intensity was varied over more than 6 log units. The pupils of the mice were imaged with an infrared video camera and recorded on videotape. The pupil area was measured by digital image analysis. Results: Fully dark adapted murine pupils had an area of 2.29 ñ 0.35 mm^2; the mimimal pupil size at saturating intensity was 0.10 ñ 0.05 mm^2. The steady-state pupil area declined to half its dark adapted maximum when ganzfeld luminance was 10^-5 scotopic cd m^-2; pupil area declined to to 20% of the dark-adapted magnitude at about 10^-3 scotopic cd m^-2. Conclusions: The mouse pupil can regulate retinal illumination by a factor exceeding 20. The neural mechanism that determines steady-state murine pupil size is extremely sensitive to retinal illumination and under these experimental conditions is controlled almost exclusively by rod signals. This follows, since the ganzfeld illuminance (10^-5 scotopic cd m^-2) that causes the pupil to constrict to half its dark-adapted value corresponds to only about 0.1 photoisomerizations per rod per sec, while 80% reduction in pupil area occurs at about 10 photoisomerizations per rod per sec. Based on this exquisite sensitivity it seems likely that the murine pupil functions to protect a retinal circuit that can be driven into saturation at extremely low quantal absorption rates. The principal candidate retinal circuit is that of the rod bipolar … AII amacrine cell … on-beta ganglion cell, whose single-photon sensitivity and high gain renders it susceptible to saturation at the extremely low light levels at which the mouse pupil contracts.
Supported by NIH EY-02660 and Penn Therapeutic Initiative for Retinitis Pigmentosa. _

Paul J. May, PhD and Wensi Sun, MD, PhD
Departments of Anatomy and Ophthalmology, U. of Mississippi Med. Ctr., Jackson, MS Department of Ophthalmology and Visual Sciences, Vanderbilt Univ., Nashville, TN

Morphology and Connections of the Olivary Pretectal Nucleus of the Macaque Monkey.

The olivary pretectal nucleus is a critical relay in the pupillary light reflex pathway. However, as its morphological and connectional characteristics have not been well defined in primates, we undertook its study in macaque monkeys. Retinal afferents to the olivary pretec- tal nucleus were labeled by placing WGA-HRP in the vitreous chamber, while injections of this same tracer were made into midbrain, at the level of the rostral oculomotor nucleus, to retrogradely label olivary neurons presumed to project to the Edinger-Westphal (E-W) nucle- us. A dense retinal terminal field was discretely confined within the olivary nucleus and co-localized with retrogradely labeled neurons. Ultratructural examination revealed direct synaptic connections between the labeled retinal terminals containing spherical vesicles and labeled projection cells. The morphology of the olivary neurons was demonstrated by injecting biotinylated dextran amine along the path of the crossed olivary projection. The somata of the olivary cells were mainly located along the periphery of the nucleus. Their dendrites were almost entirely directed toward the core of the nucleus where they arborized extensively. This organinization would allow input convergence to produce broad retinal fields. In a final experiment, the olivary nucleus projections were labeled with the anterograde tracer biocytin and the ciliary ganglion was injected with WGA-HRP to retrogradely label preganglionic motoneurons. These motoneurons were distributed in the E-W nucleus as a column running rostrocaudally above the oculomotor nucleus and extending into the anteromedian nucleus. Anterogradely labeled olivary axons arborized bilaterally at various points in the supra- oculomotor area, but labelled terminal puncta only obtained close relationships with a small portion of the labeled preganglionic motoneurons. These were located ventromedially in the E-W nucleus, within the middle third of its rostrocaudal extent. These target cells presumably represent the pupillary component of the preganglionic motoneuron population. A lateral vis- ceral column was not seen, although a reciprocal connection between the ventrolateral central gray and the pretectum was. Together, these data provide strong evidence confirming a retino- olivary-preganglionic circuit for the pupillary light reflex.
Support: NIH Grant EY09762 (PJM)

S. Merritt(a), P. Mercer(a), W. O'Neill(b), S. Yoon(b), A. Keegan(a), S. Hale(c) and J. Myerson(c)
(a)Center for Narcolepsy Research, University of Illinois at Chicago (UIC), (b)Department of Electrical Engineering and Computer Science (UIC) and (c)Washington University

Pupillary Responses And Cognitive Processing Intensity Of Narcoleptics And Controls

Small, significant increases in pupil size have been shown to reflect increasing cognitive processing demands. Task difficulty and individual ability have an effect on pupil dilation, a measure that also reflects arousal and indirectly, increased cognitive effort. While many people with narcolepsy report memory and cognitive performance difficulties presumably due to the excessive daytime sleepiness associated with this disorder, the majority of cognitive task laboratory studies have found their performance to be comparable to matched controls. We hypothesized that the narcoleptics we studied (N=6) would achieve performance equivalent to controls (N=6), but would experience a greater cognitive load and expend greater cognitive effort as reflected in larger increases in pupil diameter in response to a digit-span memory task of increasing difficulty. Stimuli were presented using an audiotape beginning with a 3 number set presented in 2 sec intervals up to a set size of 7 digits with no recall errors noted in any of the sets. The pupil diameters of both eyes were recorded simultaneously at 256 Hz with a computer-controlled pupillometer. Two seconds after the last digit was presented, the subjects were asked to repeat the set. Following cleaning and downloading to 16 Hz, pupil records were analyzed by set size using linear regressions of pupil diameter on total digit memory load from the end of the digit set to the onset of the "repeat" signal. We found significant differences (Kullback-Leibler chi square statistic, df=5) between the regression slopes (p<.01), regression intercepts (p<.05), regression slope covariance matrices (p<.001) and regression intercept covariance matrices (p<.001) for the narcoleptic and control subjects with the narcoleptics showing significantly greater amount and rate of increase in pupil dilation. While pupil dilation increased for both subject groups as a function of digit set size, we suggest that the greater dilation among narcoleptics reflects the greater cognitive load they experienced to accomplish the same task with the same proficiency as matched controls. Based on these findings, our supposition is that narcoleptics' complaints about memory tasks, especially with demanding, externally paced tasks, may occur because of the difficulties they experience in sustaining a high level of arousal and the subsequent effort required to complete the tasks.

S. Merritt, H. C. Schnyders, T. Kotsos and P. Mercer
Center for Narcolepsy Research, The University of Illinois at Chicago

Is Pupillometry Sensitive to Circadian Aspects of Sleepiness?

Among normal, adequately rested people without any evidence of a sleep disorder, sleepiness is an ultradian phenomenon that is commonly experienced upon awakening, at bedtime and about 12 hours after the mid-sleep period. The more widely used measures of physiologic sleep tendency, the Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT), demonstrate a biphasic sleep rhythm across various age groups. On the MSLT, sleep latency (i.e., the time it takes to fall asleep) is significantly decreased during the midday nap opportunities while on the MWT ability to stay awake is significantly decreased at these times. The purpose of this study was to determine if the Alertness Level Test (ALT) demonstrates pupil behavior that is consistent with the diurnal augmen-tation of sleep tendency exhibited in the MSLT and MWT. During the ALT 15 minutes of pupil diameter data are recorded at 256 Hz while the subject sits quietly in the dark with instructions to try to stay awake. Six normal healthy volunteer control subjects without any evidence of a sleep disorder participated in one day of alertness level testing at 1000, 1200, 1400 and 1600 hours after having obtained their usual sleep the previous night. Pupil diameter data were cleaned and downloaded at an 8 Hz rate. Mean pupil diameters were calculated in 15 second epochs from 5 thru 11 minutes and plotted for each subject for each data collection period. Visual inspection suggested that 4 of the 6 subjects showed a circadian trend in pupil behavior. However, 2 subjects showed patterns consistent with what has been described as homeostatic pressure for sleep due to their recent sleep patterns which may have overridden any circadian influence. Additional analyses based on the pupil staging proposed by Yoss revealed fluctuations in the percent of maximum pupil dilation for some epochs. Results from a repeated measures ANOVA by individual for each time period, and linear regression of pupil diameter by epoch across subjects appearing to demonstrate a circadian effect will be presented. Based on this small sample of subjects, analyses suggest that pupillometry may be sensitive to both homeostatic and circadian influences on level of alertness and, therefore, useful in screening for excessive sleepiness when done in conjunction with additional subjective and observational measures of health behavior and sleep-wake patterns.

Paula Moore and Randy Kardon M.D. Ph.D.
University of Iowa and Veterans Administration Hospital, Department of Ophthalmology, Neuro-ophthalmology Division, Iowa City, Iowa.

Comparison of the Multifocal "ERG Field", "Pupil Field", and Visual Field in Normal Subjects.

Purpose: To compare the topographic sensitivity of the normal retina using three different perimetric responses in the same individual: 1) the multifocal electroretinogram, 2) the pupillary light reflex, and 3) conventional light sense perimetry. This was done to understand the similarities and differences between the three different types of perimetry. Methods: Normal subjects were tested under monocular viewing conditions over a 30 degree angle of field in each type of perimetry. Multifocal electroretinograms (VERIS) were obtained at 5 different stimulus light intensities (95% contrast): 50, 100, 200, 300, and 400 cd/m2 using a 9mm dilated pupil under photopic conditions. Pupil perimetry was obtained using a 1.7 degree stimulus in one test and a 4 degree stimulus in another over a luminance range from 31.8 cd/m2 to 318 cd/m2 (100-1000 asb), under low mesopic conditions. Visual threshold was obtained using conventional automated perimetry under mesopic conditions. Results: There was some variation in perimetric topography between individuals and between the different types of perimetry. For multifocal electroretinography, the central field was more peaked compared to pupil perimetry and visual threshold perimetry when the B- wave amplitude was scaled according to the area stimulated in each location (nanovolts/degree2). Some subjects also showed that the temporal field was more electrically responsive (especially inferior temporal field) at higher stimulus intensities. Pupil perimetry showed more pupil contraction toward the central field and more sensitivity in the temporal field as well (the inferior nasal field was the least responsive). Conclusions: The three types of response perimetry vary somewhat in their response topography and also vary between individuals. The topography also shows some asymmetries between the temporal and nasal field and superior and inferior field, especially at brighter suprathreshold stimuli. These topographical differences may be important in understanding how different levels of information processing are integrated at different locations in the visual system and how they are affected by disease processes.

M.I.K. Norrish and J.D. Mollon
Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, CB3 3EB, United Kingdom

Relative Potency Of Various Stimulus Attributes In Evoking The Transient Pupillary Light Reflex: A Signal Cancellation Technique

The input to the pupillomotor system is thought to be organised into phasic and tonic pathways and the response of the pupil into transient and sustained components. This study investigates the relative potency of inputs to the transient response using a technique of signal cancellation. Two non-overlapping stimuli are presented to the subject. They are sinusoidally modulated in intensity and are in anti-phase. The frequency of modulation for most of the experimental conditions was set at 2.6 Hz, in order to isolate the transient (AC) component of the pupillary light response. One stimulus, the reference, is fixed in intensity and modulation depth. The intensity of the other stimulus is varied so as to establish the response null at which the transient component of the pupil response is minimised. Using this technique it is possible to investigate the relative potency of various stimulus attributes in controlling the transient component of the pupillary light response. The variation of responsivity of the transient component of the pupillary light reflex with stimulus eccentricity was investigated over the central 10 degrees. This function is conical and is centred at the fovea. The potency of a stimulus decreases as eccentricity is increased. Variation of stimulus size showed that for the range of sizes used, up to 7 deg in diameter, the transient component of the pupillary response is determined by the total light flux. The method is a general one and could be used to measure the transient pupillary response as a function of other stimulus variables, such as chromaticity or spatial frequency.

Dr.-Ing. Peter Roessger
Daimler Benz AG, Forschung und Technik

The Pupillometric Measurement of Driver Mental Workload

Pupil dilation under mental workload had been a subject to psychological research during the sixties and the seventies. At the end of the eighties technologies had been developed that allowed to measure pupil size outside the laboratory. The development of pupillometric measurement from a tool used under strictly limited laboratory conditions to a tool used under real work conditions will be described in the presentation. The influence of mental work load on the pupil diameter is much smaller than the influence of changing brightness. There is no interaction between these two influences. So it is possible to free the pupil diameter from the contamination by light with a linear mathematical procedure. The results of a driving experiment on public roads in Berlin (Germany) will be presented. The subjects drove a Mercedes Benz 300D, with the Dornier Eye-Tracking-System installed. This equipment had been developed to registrate driver eye movements while driving on public roads. It measures the pupil diameter with 50Hz. In addition equipment had been installed to measure the brightness outside the car. The results show that there is a clear influence of the difficulty of the driving task on the pupil. During right turns and during left turns occurred the largest pupils, the smallest while waiting at a red traffic light. Further results will be presented. Perspectives of the method as a tool in ergonomic research will be discussed.

Michael L. Rosenberg, Martin Kroll NJ
Neuroscience Institute, Edison, NJ and Johns Hopkins Medical School

Pupillary Hippus: An Unrecognized Example of Biologic Chaos

The conventional model for the activity of the pupils is that of a linear control model. This predicts that the pupil size would vary inversely with the amount of incoming light and in a constant light would remain a constant size. A typical recording of pupil size under such circumstances, however, shows marked spontaneous activity with an irregular pattern of aperiodic oscillations. Previous works have suggested that this spontaneous activity was random, i.e. not governed by deterministic properties and could be interpreted as noise. We analyzed pupil size vs. time from six subjects and compared these time series with those from a pair of fake eyes as well as with surrogate date sets generated from the original data sets. Non-linear analysis including correlation dimension, Hurst exponents, Lyapunov exponents, and a power spectrum all support the hypothesis that the pupil oscillations were generated by a deterministic system that is chaotic. The phase space analysis also showed strong evidence that the movements were not random. Simple inspection of the tracings showed that the oscillations often have a clear cut pattern that is reproduced over 10-30 second intervals. Overall the data clearly show that pupillary hippus is not random, rather it is the result of a deterministic process showing nonlinear behavior including chaos.

Dirk Sandner, Bengt Bartsch, and Franz Thoss
Carl Ludwig Institute of Physiology, University of Leipzig, Germany

Parallel Oscillations in the Pupil System and the Heart Rate, forced by periodic work load.

Spontaneous oscillations of the diameter of the pupil and the pupillometric threshold are coupled very weakly with oscillations of the heart rate. The common influence of the autonomic nervous system seems to be hidden by a lot of different influences from other systems. To elucidate the role of the activity of the autonomic system, we have forced oscillations of this activity by a weak work load. In intervals of 3 minutes our subjects had to pull the handle of a hand ergometer for 30 seconds. The total time of each of these investigations was 30 minutes. ECG, pupil diameter and amplitude of the consensual light reflex (threshold conditions) were recorded synchronously during the investigation time. The influence of the pupil diameter on the reflex amplitude was eliminated pharmacologically. The results show synchronous oscillations of heart rate, pupil diameter and pupillary threshold at the frequency forced by the load and its higher harmonics. During the load the heart rate increases due to an increase of the activity of the sympathetic system. The cross correlations among the three parameters show the pupil diameter to be in step with the heart rate: The increase of the heart rate goes parallel to an increase of the pupil diameter. In contrast, the amplitude of the pupil reactions is shifted in phase by 180 degrees. This means in relation to the heart rate: Increased heart rate goes in step with decreased amplitude of the pupil's light reflex. This result is in good agreement with the findings of Loewenfeld: Increased sympathetic acti vity decreases the light reflex amplitude.

Lawrence W. Stark
Neurology and Telerobotics Unit, University of California at Berkeley, CA

Bioengineering Control Approach To The Pupil: 1957 To 1997

The early experiments on feedback control of the pupil (1957-1959) also involved a model composed on transfer function elements that imposed certain constraints on our thinking about the pupil. However, it was flexible enough to deal with such interesting topics as stability and oscillation. Noise characteristics could be defined and used as additional information concerning the various internal mechanisms of the pupillary response to light. Light processing mechanisms in the retina and subsequent way stations in brain stem and above, required a number of interesting models to be developed, including such important nonlinear phenomena as the "pupil size effect," which described the ability of the pupillary system to demonstrate both pupil escape and pupil capture under the appropriate operating conditions. Motor mechanisms were studied from a number of points of view, including evidence for an active dilator. The length tension properties of muscle now explained in terms of the molecular biology of the sliding filament model, dominate certain aspects of pupillary behavior, since the pupil muscles change their length operating level so widely. Nonlinear analysis has also used the pupil in a series of paradigm Wiener kernel functional descriptions. A number of clinical syndromes could be defined with the same experimental and modeling procedures used to study the normal pupil. Finally, the role of the pupil in the triadic response to light and accommodation was also explored. Forty years of research has rather opened more problems than solved earlier pressing questions.

Stuart R. Steinhauer, Ruth Condray, Daniel P. van Kammen, George G. Dougherty, Jr.
Biometrics Research, Dept. of Psychiatry, University of Pittsburgh School of Medicine and VA Pittsburgh Healthcare System

Sympathetic and Parasympathetic Components of Pupillary Dilation During Cognition: Evidence From Normal and Psychiatric Data

Differential contributions of sympathetic and parasympathetic activation to pupillary dilation have been modelled for a variety of information processing requirements. We have hypothesized that tasks involving sustained effort and attention, as well as motor initiation, result in dilation through inhibition of parasympathetic activity at the Edinger- Westphal complex. In contrast, immediate processing of salient information is hypothesized to be related to activation of the sympathetic pathway, resulting in a later dilation. Implications of the general model will be briefly reviewed. Initial confirmatory evidence was found in the pupillary responses of 17 normal controls compared to 16 schizophrenic patients, and to 31 non-schizophrenic siblings of the patients. Principal Components Analyses of averaged pupillary responses revealed three major underlying components, replicated for each group and each of two tasks separately. Two of these components matched initial predictions of the original model. In an analysis utilizing all groups together, only the factor scores associated with presumed sympathetic activity, which was related to outcome probability of stimuli, showed decreased activity in the patients and their relatives. The factor scores for the component associated with presumed parasympathetic activity did not differ among groups. The third component, associated with anticipatory processes, and possibly related to parasympathetic inhibition, did not differ among groups. Pupillary findings suggested that a major deficit in schizophrenia-related disorders represents difficulties in the utilization of information, but not in motivation to perform. Implications for pupillary assessment to guide future neuroimaging studies will be discussed.

Stuart R. Steinhauer, Lisa A. Morrow, Ruth Condray, Annette Kasparek
Biometrics Research, Dept. of Psychiatry, University of Pittsburgh School of Medicine and VA Pittsburgh Healthcare System

Pupillary Responses to Cognitive Activation in Patients and Workers Exposed to Organic Solvents

The deleterious effects of exposure to organic solvents include changes in cognitive and personality functioning. The majority of earlier research emphasized neuropsychological test performance, with little direct measurement of nervous system activity during demanding cognitive tasks. To address that deficiency in the literature, we have examined pupillary, event- related potential, and cardiac activity in subjects who either have had 1) significant exposures to toxic organic solvents leading to documented clinical impairment, or 2) workers who are exposed to solvents on an ongoing basis. Averaged pupillary responses were recorded from 14 patients meeting criteria for mild toxic encephalopathy, Type 2A/2B, contrasted with 18 control subjects. Subjects first performed an auditory task involving Counting of a rare stimulus, followed by a task involving separate motor responses to the same rare and frequent stimuli (Choice Reaction. Maximum amplitude of pupillary dilation to rare tones was decreased among the patients. In addition, patients showed an unusual pattern of tonic pupil diameter across the tasks. While normal controls show a decrease in diameter between the Counting and Choice Reaction tasks, attributed to habituation, patients showed either no change or increased diameter during the Choice Reaction task. This effect was also observed for overall heart rate in patients. These autonomic effects are not seen in psychiatric patients, and appear to be associated with greater difficulty in performing more complex discriminations or cognitive decision making. At 1-3 year follow-up, 6 of 8 patients showed a continued or exacerbated reactivity. In addition, the ongoing effects of exposure have also been studied in 23 union painters who have not had any significant clinical complaints, but who are continually exposed to a variety of organic solvents. Although no differences in peak dilation were observed, the lack of habituation described for the exposed patients was also present in the painters, regardless of whether they had been recently exposed (<67 hours) or had been exposure free for 4 or more days. Implications of these findings for limbic system activity, including models of kindling, will be presented.

E Szabadi, P Bitsios, C M Bradshaw
Department of Psychiatry, University of Nottingham, Queen’s Medical Centre, Nottingham NG7 2UH, UK

Central Noradrenergic Regulation of Pupillary Functions

Noradrenergic neurones of the brain stem innervate sympathetic spinal column nuclei and exert an excitatory influence on the sympathetic control of the pupil. These neurones also exert a dual inhibitory control on the preganglionic parasympathetic neurones in the Edinger-Westphal nucleus: directly from the locus coeruleus, via inhibitory a2- adrenoceptors, and indirectly from the A1/A5 nuclei via the hypothalamus [1]. Thus, it can be predicted that a decrease in the activity of the central noradrenergic neurones will result in both a sympatholytic and a parasympathomimetic effect on the pupil, whereas an increase in central noradrenergic activity would evoke reverse effects. Age- or disease-related degeneration of central noradrenergic neurones may underlie the sympathetic deficit (reduced pupil size and attenuated darkness reflex) observed in old age and Alzheimer’s disease [2]. Furthermore, “switching off” of the central noradrenergic neurones via activation of somatodendritic inhibitory a2-adrenoceptors (“autoreceptors”) may be responsible for both the sympatholytic (miosis, prolongation of the recovery time of the light reflex) and the parasympathomimetic (miosis, reduction of light reflex amplitude) effects of clonidine in man. Conversely, enhancement of central noradrenergic activity may underlie both the sympathomimetic (increased pupil size, shortened recovery time of the light reflex) and the parasympatholytic (increased pupil size, reduced light reflex amplitude) effects of anxiety [3]. Enhancement of the noradrenergic inhibition of neurones in the Edinger-Westphal nucleus may explain the parasympatholytic effects of drugs which block noradrenaline uptake. Thus it has been shown that noradrenaline uptake inhibitors (desipramine, venlafaxine, reboxetine), apart from causing mydriasis, prolong the latency and reduce the amplitude of the light reflex response.

1. Szabadi E, Bradshaw C M (1996) J Psychopharmacol 10 (Suppl 3), 6-18.
2. Prettyman R et al. (1997) J Neurol Neurosurg Psychiat 62, 665-668.
3. Bitsios P et al. (1996) J Psychopharmacol 10, 279-287.

Christiane M. Thieme, Hans Joachim
University of Heidelberg, Institute of Legal and Traffic Medicine

The Influence of Acute Cannabis Use on the Pupillary Light Reflex

Purpose: In Germany you are not allowed to drive a car under the influence of alcohol or other drugs, which have an effect on the traffic safety. In this session of parliament we will get a new law prohibiting driving under the influence of cannabis, morphine, heroin, cocaine. The change of pupil behavior after the consumption of drugs is under discussion as a pretest to detect drug users in traffic. Therefore, we tested the influence of marijuana and hashish on the pupillary behavior in a field study. Method: 50 moderate and frequent cannabis using volunteers aged between 18 and 35 years were examinated by infrared video pupillography. In a pretest we detected latency, constriction time, baseline diameter, and constriction amplitude. After the subjects had smoking hashish or marijuana we repeated the measurement under the same conditions. The blood THC, 11-OH THC, THC-COOH levels were determined. A control group of 50 non user was also tested under the same conditions. Results: THC serum concentrations between 1,31 and 45,61 ng/ml and 11-OH-THC serum concentrations between 0,17 and 18,57 ng/ml were observed (GC/MS). The correlations between serum concentrations of THC, 11-OH- THC,and THC-COOH were low or moderate but significant. Four persons who also used cocaine were excluded from the study. The comparison of the means of dependent and independent samples does not show a significant difference between the pretest group and test group and between the test group and the control group. Some perspectives for further research were discussed.

Franz Thoss, Bengt Bartsch, and Dirk Sandner
Carl Ludwig Institute of Physiology, University of Leipzig, Germany

Oscillations of the Pupillometric Threshold and the Heart Rate - are they Related?

In a previous investigation (Thoss, Bartsch, Getaneh; Haigerloch 1995) oscillations of the pupillometric threshold were analysed in 10 subjects. The resulting spectra showed strong variability both intra- and interindividually. We found period durations between 1 minute and 26 minutes. The question for the origin of these oscillations is not answered as yet. One source could be oscillations of the activity in the autonomic nervous system. Therefore, we investigated in parallel pupillometric threshold, pupil diameter, and heart rate. If the origin of the oscillations would be within the autonomic system, identical frequencies should be found in all three parameters. We recorded ECG, pupil diameter and the amplitude of the consensual reflex to very weak (threshold) light flashes for 30 minutes. From the records the cross power spectra and the cross correlation functions were calculated. Only four of our fourteen subjects showed remarkable oscillations of the investigated parameters at the same frequency among many oscillations with different frequencies. In the spectra of all other subjects common frequencies of these parameters are very weak or missing. From these results we can conclude: Oscillations of the activity within the autonomic nervous system seem to contribute to the oscillations of the pupillometric threshold, but only to a small extent. Even the spectrum of the pupil diameter itself is very different from that of the ECG.

John P. Dal Santo*, Stuart A. Tousman*~, Judi K. Gerstein, Nicklaus Dal Santo*
*Regional Sleep Disorder Center, Rockford, Il, *MCJ Inc., Rockford, Il.
~Associate Professor, Department of Psychology, Rockford College, Rockford, Il.

Pupillometry and Trucking Fatigue

The purpose of the present research was to determine if fatigued truck drivers show different pupillary responses than non- fatigued truck drivers. A total of 166 truck drivers were stopped at a safety checkpoint in a large midwest city. They answered survey questions about their level of fatigue and then volunteered to have 3 pupilscans taken of their eyes. The PupilScreenä (Applied Science Laboratories) flashed a green light onto the pupil and recorded a number of pupillary response variables including constriction velocity and reflex amplitude. Statistical results indicated that fatigued truck drivers had significantly faster constriction velocities and larger reflex amplitudes than non-fatigued truck drivers. Time of day and Stanford Sleepiness Scale scores were not correlated with pupillary responses. The results of this research suggest that pupil physiology can be used as an accurate indicator of fatigue in truck drivers.
Research supported by: Regional Sleep Disorder Center and MCJ Inc., Rockford, Il., Applied Science Laboratories, Bedford Ma., Illinois State Police, Special consideration: U.S. Army Aeromedical Research Laboratory, Fort Rucker, Al.

Rüdiger Schmid, Bärbel Wilhelm, Helmut Wilhelm
University Eye Hospital Tübingen, Department of Pathophysiology of Vision and Neuro-ophthalmology

Contraction Anisocoria & Retinal Pupillomotor Sensitivity: Hemifield And Perimetric Stimulation

Purpose: Differences between the nasal and temporal retinal hemifield may contribute to the contralateral RAPD seen in optic tract, thalamic or midbrain lesions. To understand the architecture of the pupillary pathway, it is important to know about the amount and the prevalence of naso-temporal differences and of contraction anisocoria in normal individuals. Several studies in the past reported results corresponding only partially. We studied naso-temporal differences of the central visual field in normals with direct and consensual hemifield-stimuli (42 individuals) as well as pupil perimetry (43). Methods: After 10 minutes adaptation, infrared video pupillography was performed (25 Hz realtime), with hemifield stimuli and pupil perimetry. Hemifield stimuli were half circles with 10 radius and 2 horizontal offset from fixation point, stimulus luminance was 4.6 cd/m2 (contrast 0.78); pupil perimetry was performed with 15 test spots of 2 in the 20 visual field at a stimulus luminance of 54 cd/m2 (contrast 0.98). Stimulus duration was always 200 ms. Alternately nasal and temporal hemifields were stimulated 5 times each, directly and consensually in both eyes, thus testing 4 different channels for each eye. After a break, pupil perimetry was performed (four trials). The pupillograms where evaluated off-line by a curve fitting procedure. Results: The mean values of all pupillograms showed very subtle differences between the four channels tested by hemifield stimulation. Nasal retina proved to be more sensitive than temporal retina, both in hemifield stimulation and perimetry. Nasal inferior retina emerged as the most sensitive quadrant of the perimetric retinal field, the temporal superior retina as the least sensitive. On nasal retina, the direct response exceeded the consensual response, whereas there was nearly no difference on temporal retina. A considerable interindividual variability existed. Conclusion: Naso-temporal differences in pupillomotor sensitivity of the central retinal field exist, both for larger stimuli and for small perimetric stimuli. However, they are too subtle to explain severe RAPDs of 0.6 log units and more encountered in many patients with tract lesions and other lesions of the afferent path to the pretectum. Given an asymmetric crossing from pretectal nuclei to nucleus Edinger-Westphal, our findings of contraction anisocoria suggest a partial crossing of temporal fibres to the contralateral pretectum. Such a crossing in the chiasm would also cause a contralateral RAPD in tract lesions.

Jennifer B. Williams 1, Anton Reiner2, Paul D. R. Gamlin1
1Department of Physiological Optics, University of Alabama at Birmingham, 924 South 18th St. Birmingham AL 35294
2 Department of Anatomy and Neurobiology, University of Tennessee-Memphis, Memphis, TN 38103.

Neuroactive substances in the primate pretectal olivary nucleus: Their possible role in the modulation of the pupillary light reflex

Resting pupil diameter and the responsiveness of the pupillary light reflex depend on the level of alertness of the subject. When the subjects are fatigued the pupils constrict and become less responsive to visual stimuli. This modulation by alertness is believed to result from brainstem influences on the Edinger-Westphal nucleus (EW). Recently we have observed in the pretectal olivary nucleus (PON), a nucleus which receives direct retinal input and projects to the EW, that luminance neurons increase their spontaneous firing rate as monkeys become less alert and their pupils constrict. This would indicate that the PON as well as the EW is a site of pupillary modulation. To better understand the potential neurotransmitters involved in this modulation, we used immunohistochemical methods to study the localization within this nucleus of the neurotransmitter serotonin (5HT), the neuropeptides substance P (SP) and enkephalin (ENK), the calcium binding proteins calbindin (CALB) and parvalbumin (PARV), acetycholine receptors (AChRs), several AMPA type glutamate receptor subunits (GluR1, GluR2/GluR3, and GluR4), and kainic acid (KA) type glutamate receptor subunits (GluR5/GluR6/GluR7). Standard peroxidase-antiperoxidase immunohistochemical methods were employed on paraformaldehyde fixed rhesus monkey. The neuropil of PON was distinctly rich in SP+ and ENK+ fibers and also contained some 5-HT+ fibers. Some PON neurons were CALB+ and PARV+. Essentially all PON neurons were rich in AMPA GluR2/3 AMPA subunits, and a few exhibited GluR5/6/7 KA subunits. These findings have provided histochemical criteria by which to identify PON and its output axons to the EW, and demonstrate the presence of a number of neuroactive substances that may modulate or control the pupillary light reflex at the level of the pretectum.
Supported by NIH grants EY09380 to PDRG and E05298 to AR

Harry J. Wyatt
Schnurmacher Institute for Vision Research, State College of Optometry, New York, NY

Pupil Sector Dilation Along Different Meridians: Interrelationship of Mydriatics, Convectional Flow, and 3-D Configuration of the Anterior Segment

“Sector dilation” by focal application of sympathomimetics has been used for some time; in contrast, the procedure reportedly fails with parasympatholytics. In actuality, the situation is somewhat more complex than usually recognized, because (i) the target muscles for different drugs (dilator and sphincter) differ greatly in their configuration, and (ii) anterior chamber convectional flow has been shown to play a very substantial role in anterior segment pharmacokinetics (J. Oc. Pharm. & Ther. 12: 441). The effect of a given drug presumably depends on these factors, and therefore should also depend on the locus of drug application. Three subjects were studied in detail. Phenylephrine or tropicamide was administered with a pledget applied to nasal, inferior, temporal, or superior limbus for 0.5-1.0 min. In some experiments, a drop of fluorescein on the pledget permitted visualization of the application locus. Standard drop application was employed as a control. Pupil shape and placement during mydriasis were determined photographically (Vision Res. 35: 2021). Changes relative to the reference (pre-drug) state were evaluated from the difference shape, defined by: Difference.shape = Current.shape – (r.current ¸ r.reference) x Reference.shape Both tropicamide and phenylephrine produced "sector dilation"; however, phenylephrine was about twice as effective. For both drugs, inferior and temporal applications were most effective, and superior and nasal applications were least effective. Application of tropicamide at the most effective loci also gave the shortest latency (shorter than the latency for drop application). The latency for phenylephrine was nearly independent of locus. Some aspects of the present results—especially the superior/inferior asymmetry—can be understood in terms of convectional flow and the configuration of relevant structures. Some other aspects—particularly the nasal/temporal asymmetry—remain to be explained.

K. Yamaji 1, Y. Hirata 2 and S. Usui 1
1 Toyohashi University of Technology, Toyohashi, Aichi, JAPAN
2 National Space Development Agency of Japan, Tsukuba, Ibaraki, JAPAN

Evaluation of the Autonomic Nervous System Activity in Hyper- and Hypo-Gravity using Pupillary Response to Comb-like Flash

[Introduction] Since the autonomic nervous system(ANS) plays a major role when we adapt to the new environment, it is important to monitor ANS activity of astronauts under the micro-gravity. In the previous colloquium, we proposed a method for assessing the ANS activity from pupillary flash response. In this study, we improved the method and attempted to evaluate the sympathetic and parasympathetic nervous activities under hyper- and hypo-gravity during a parabolic flight. [Improved method] The previous method enables a separate assessment of sympathetic and parasympathetic nervous activities from changes in pupillary single flash response. However, relatively low gain of the dilator system compared with the sphincter makes it difficult to detect change in the sympathetic nervous activity. This problem was improved by using comb-like flash stimulus which activates dilator system more efficiently than single flash stimulus. As in the previous method, maximum constriction velocity(Vcmax) and recovery amount(RA) are evaluated by taking effect of range nonlinearity into account. Validity of the improved method was proved by experiments using autonomic nervous drugs. [Parabolic flight] experiment The experiment was conducted by a small jet-plane. About 20 seconds hypo-gravity and hyper-gravity before and after hypo-gravity can realize in a parabola. A male university student volunteered as a test subject. [Result] In hyper-gravity, significant change in activities of neither sympathetic nor parasympathetic nervous system was concluded in comparison with the ground 1G condition. On the other hand, in hypo-gravity, the sympathetic nervous activity was slightly activated, whereas the parasympathetic nervous activity was clearly inhibited.

Mario Zulauf, Martin Schelling, Oliver Bergamin, Andreas Schötzau, Ara Hagopian, and Birgitta Henzi
University Eye Clinic Basel, P O Box CH-4012, Basel, Switzerland Fax: +41 (61) 265-8741; 

Simultaneous Pupil and Conventional Perimetry.

Purpose: To evaluate if it is possible to perform simultaneous pupil and conventional (i.e. psychophysic light-sense) perimetry. The hypothesis is that the pupillary light reflex (PLR) could serve as an additional reliability parameter in conventional perimetry, and/or, near psychophysic threshold stimuli would improve the tested subject's attention during pupil perimetry and reduce sleep-wave artifacts. Materials and methods: Twelve healthy normal volunteers (age: 31.8; 23-62 years; 6 females, 6 males) were examined with a modified Octopus 1-2-3 automated perimeter which measures the pupil area at 50 Hz. Background (1 cd/m2), stimulus size (0.43 ) and stimulus duration (100 ms) were chosen similar to standard Octopus perimetry. Stimuli were presented at 4 different brightness levels (5.2 ­ 413.4 cd/m2). The pupillary light reflex was evaluated after the test by 4 experts visually on screen and by an algorithm developed by our research group which fits linear regressions and polynomials into the pupil tracings to define the onset of the PLR and the maximal constriction of the pupil. Results: The algorithm was 20% more conservative than the experts to recognize the existence of a PLR. To elicit (and detect by the algorithm) a PLR with a chance of 50%, stimulus brightness averaged at an eccentricity of 0 /0 5.2 cd/m2; at 8 /8 65.4 cd/m2, at 8 /-8 52 cd/m2, at 20 /20 164.3 cd/m2 and at -20 /-20 206.8 cd/m2. As expected, the PLR decreased with age. Conclusions: The results suggest that the evaluation of the PLR during standard Octopus automated perimetry might serve as a reliability parameter but does not permit to detect minor flaws in cooperation. Stimulus size 5 (1.7 ) is preferred for simultaneous pupil and conventional perimetry. Based on these results, we are currently developing algorithms which permit to perform simultaneous both perimetries by 'online' evaluation of the PLR.
Supported by grant #32-43624.95 of the Swiss National Fund.

Barbara Wilhelm, Helmut Wilhelm, Dietrich Widmaier, Karl-Heinz Rühle, Holger Lüdtke
Department of Pathophysiology of Vision and Neuroophthalmology, University Eye Hospital, Tübingen

Pupillographic Sleepiness Test In Patients With Sleep Apnea Syndrome

Introduction: Objective assessment of sleepiness in therapy control of patients with sleep apnoea syndrome (SAS) is a strong demand in sleep medicine. This study was done to evaluate whether spontaneous pupillary behaviour in darkness is altered in SAS patients and how far it may be changed by therapy. Slow pupillary oscillations in darkness proved to be a sensitive indicator of sleepiness in previous studies. Methods: 38 patients with SAS (diagnosed in sleep laboratory) were examined by means of infrared-video pupillography for 11 minutes in complete darkness around 10 a.m. and 2 p.m. Pupillograms underwent mathematical analysis to determine the amount of spontaneous slow pupillary oscillation. The recordings were repeated after two nights of cPAP treatment. Results: (1) Patients with SAS show a clearly higher amount of slow pupillary oscillations in darkness than healthy alert normals (factor 2). (2) Patients with high apnea hypopnoea index (AHI) have significantly higher amounts of slow oscillations than patients with low AHI. (3) The same was found comparing patients with high and low scores on the Epworth sleepiness scale. A correlation was found for Epworth score and slow pupillary oscillations (quantified by fast Fourier Transformation) (4) Slow pupillary oscillations were reduced by about one third with the a.m. measurement after cPAP treatment.. Conclusions: The study shows that pupillography may be applied clinically to assess sleepiness in SAS patients and to monitor therapeutic effects.
Supported by fortuene F. 1222074.1 supported by (DFG) Deutsche Forschungsgemeinschaft WI 1066/3-1

Barbara Wilhelm, Anna Hofmann, Evelyn Schmidt, Peter Streicher, Helmut Wilhelm, Holger Lüdtke, Henner Giedke1 Department of Pathophysiology of Vision and Neuroophthalmology, University Eye Hospital, Tübingen;
1Department of Psychiatry, University of Tübingen

Pupillographic sleepiness test in normals: Circadian rhythm and sleep deprivation

Purpose. Spontaneous pupillary behaviour in darkness provides information about a subject’s level of sleepiness. How does spontaneous pupillary behaviour vary in normals when measured at different daytimes? Does this circadian rhythm show similarities to that of other vigilance tests? To which extend do sleep-related changes increase in sleep-deprived normals? Pupillographic Sleepiness Test (PST). Spontaneous pupillary behaviour in darkness is recorded over a period of 11 minutes (= 8 times 2048 data points) by means of infrared video pupillography. Further details see methodological paper, same session. Results. Circadian Rhythm. 13 young adults took part in an 30 hours experiment lasting from 8 a.m. to 1 p.m. the following day. They were measured by PST every two hours followed by a self-rating scale (Stanford Sleepiness Scale, SSS), followed by the psychiatric part of the experiment including a concentration test (continuous performance test, CPT) and measurements of smooth pursuit eye movements (SPEM) and adjective mood scale. Power _ 0.8 Hz and PUI expressing daytime sleepiness showed lowest values at 9 a.m. and 11 p.m. corresponding to (1) peaks in pupil size at the same time and to (2) low values in self rating scales. In the course of the day power _ 0.8 Hz and PUI increased and were highest at 3 p.m. reflecting a lower vigilance level in the early afternoon. Sleep deprivation. Spontaneous pupillary behaviour in darkness was recorded every two hours in 13 healthy subjects from 7 pm to 7 am during forced wakefulness. On each occasion, comparative subjective sleepiness was assessed with a self-rating scale (Stanford Sleepiness Scale, SSS). The power of slow pupillary oscillations (_ 0.8 Hz) increased significantly and so did the values of SSS, while the decrease in basic pupil diameter was non-significant. Even though the interindividual variability of absolute values in power and PUI was high, the increase during the night was present in each individual. Power and PUI increased not only linearly but also with the square of time (ANOVA, repeated measurements, Power p = 0.025, PUI p = 0.014 ). Slow pupillary oscillations and SSS did not correlate well in general but high values of pupil parameters were almost always associated with high values in subjective rating. Conclusions. Results of pupil data analysis permit an objective measurement of sleepiness. Parameters describing spontaneous pupillary behaviour in darkness as power _ 0.8Hz and PUI increase exponentially in sleep deprivation. The circadian changes of these parameters in healthy normals reflect the slight differences in vigilance level at different daytimes and are similar to the circadian rhythm known for the MSLT (multiple sleep latency test) in young adults.
Supported by fortuene F. 1222074.1 supported by (DFG) Deutsche Forschungsgemeinschaft WI 1066/3-1

Constantin Kriegbaum, Helmut Wilhelm, Barbara Wilhelm, Frank Schaeffel
Dept. of Pathophysiology of Vision and Neuro-ophthalmology, University Eye Hospital, Tübingen

Fatigue Affects Pupillary Near Response But Not Accommodation

Purpose: The aim of this study was to demonstrate the variability of pupillary near response and accommodation during daytime. Methods: By means of real time (25 Hz) infrared video retinoscopy and simultaneous pupillography, refraction and pupillary diameter were recorded during fixation of a target at distances of 2, 3, 4 and 5 diopters in 45 emmetropic volunteers aged between 6 and 40. Measurements were performed with binocular or monocular fixation. Both eyes were measured successively in each experiment. In the first trial, the initially measured eye and the subsequently measured eye were compared. In the second trial, accommodation and pupillary near response were compared at different daytimes. Results: Pupil sizes of the second measured eyes were significantly smaller for all target distances (p<0.001). Amplitudes of accommodation were almost the same in both eyes. For normal subjects, binocular and direct accommodative responses were very similar at different daytimes. Pupil sizes before and during near fixation were smallest in the evening (significantly differing from the morning and afternoon measurements) for all target distances. There was no significant difference between morning and afternoon measurements. Conclusions: Fatigue has considerable impact on the pupillary near response, but does not influence accommodation. During repeated measurements, the initial record showed a significantly smaller pupillary near response than the following records, indicating an effect of fatigue. In the evening the pupillary near response was much more pronounced. Most subjects in our study felt more tired in the evening than at other daytimes. It is therefore likely that even daytime variation of the pupillary near response may be caused by fatigue, i.e. decreasing sympathetic activity. This effect is obviously limited to the pupil and does not show up in accommodation.

Daniel Bittner, Holger Lüdtke, Barbara Wilhelm, Helmut Wilhelm
University Eye Hospital Tübingen, Dept. of Pathophysiology of Vision and Neuro-ophthalmology

Pupillographic confirmation of optic nerve disease

The swinging flashlight test is an invaluable tool in detecting neuroretinal diseases. It may be quantified by means of neutral density filters. There have been several reports about a fairly good correlation of visual field defects and relative afferent pupillary defects (RAPD). Two studies were performed by us: First to test for correlation between visual field defect and RAPD, second to compare pupillographic parameters and RAPD in unilateral or assymmetric optic nerve disease. Methods: 1st study: RAPD was measured by grey filter balancing in 98 patients with different optic nerve disease, mainly optic neuritis, AION and compressive optic neuropathy. Visual fields were mapped using suprathreshold automated grid perimetry (Tübingen Automated Perimeter). 2nd study: In another collective of 95 patients with unilateral or assymmetric optic nerve disease (not identical with the first one), again RAPD was measured by grey filter balancing. Thereafter pupillography was performed using the Compact Integrated Pupillograph (CIP by AMTech). Time resolution was 5 ms, spatial resolution higher than 0.02 mm. A yellow LED with a maximum intensity of 10000 cd/m2 (= 250 relative units) served as stimulus. Under mesopic conditions 200 ms stimuli were presented with 2 different stimulus intensities: A baseline stimulus with a relative intensity of 8 (in some cases of very mobile pupils 4) relative units was applied in all, another intensity was chosen according to the RAPD with the purpose of pupillographically balancing the pupillary response: E.g., with an RAPD of 1 log unit, intensities of 4 and 40 relative units were chosen (RAPD-adjusted stimulus). 5 pupillograms were recorded for each eye and stimulus. Latency, constriction amplitude and baseline diameter were defined automatically. The mean values of the 5 pupillograms were calculated. The results of 72 patients that could be assigned to a distinct diagnosis (29 optic neuritis, 30 compressive optic neuropathy, 13 AION) were evaluated. Results, 1st study: We found a moderate overall correlation of visual field defect and RAPD. Specified according to the cause of the lesion, the best correlation was seen in compressive lesion, followed by optic neuritis and AION. 2nd study: On average, both baseline stimulus and RAPD-adjusted stimulus demonstrated the presence of the optic neuropathy. However, pupillography showed the RAPD on the ”wrong” side or no RAPD at all in 5 of 72 subjects if latency was considered and in 8 of 72 subjects if amplitude was considered. Constriction amplitudes to the baseline stimulus correlated better to the RAPD than latencies. The pupil responses to the baseline stimulus in the presumably normal eye and to the RAPD-adjusted stimulus in the affected eye were about the same. However, no specific difference in latencies was observed between the three diagnostic groups. Discussion: The RAPD tested by swinging flashlight test provides good information about the visual field defect, especially in compressive optic nerve lesions. Pupillography as applied here is able to demonstrate an optic nerve lesion as well, even if it fails in some cases. Constriction amplitude was the parameter that correlated best with the RAPD. In our setting it was not possible to demonstrate significant pupillographic differences between the different diagnostic groups, especially no specific latency prolongation was seen in optic neuritis.

Helmut Wilhelm, Holger Lüdtke, Andreas Körner, Barbara Wilhelm
University Eye Hospital Tübingen, Dept. of Pathophysiology of Vision and Neuro-ophthalmology

Pupillary fatigue waves – recording conditions and evaluation

1964 Lowenstein, Feinberg and Loewenfeld described a pupillary behaviour that seemed to be typical of fatigue (today in sleep medicine one would rather call it sleepiness): Slow pupillary oscillations (< 1 Hz) with amplitudes up to several mm that occured in complete darkness. This should have been of interest for sleep medicine and sleep research, because up to now no really reliable measures exist for drowsiness or sleepiness. It is puzzling that only few people took advantage of pupillography for the assessment of sleepiness (Yoss in the sixties and seventies, and in this decade Merritt and co- workers). One reason for this may be that pupillographic procedures were complicated and not optimized for stable long time recordings that are necessary for pupillographic sleepiness testing. Another reason was that the method had never been evaluated systematically. To establish infrared video pupillography as a reliable and objective test in the detection and quantification of daytime sleepiness, the definition of numerical parameters characterising spontaneous pupil behaviour adequately for further statistical procedures is an important precondition. The correct measurement of the pupil size, even if the lid or eyelashes are partially occluding the pupil, is of particular concern when testing vigilance. Methods. Pupillography was carried out in complete darkness (infrared goggles) and quietness. The volunteers were placed in a comfortable sitting position using a chin-rest. Infrared video images of the pupil were digitized in real time (25 Hz) for a duration of 11 min by means of a commercial frame grabber board (Oculus 300 by CORECO) and analyzed on-line as follows: Edge points of the pupil are detected and a double fitting procedure is carried out which correlates these edge points to a circle and excludes outliers in a second fit. Further analysis of the pupillograms is performed off-line: The first step of data preparation consists of a mathematical artifact management comprising blink detection and elimination, followed by interpolation. Second, a Fast Fourier Transformation is carried out for frequencies from 0.0 to 0.8 Hertz for each time segment of 82 seconds. Results are given in absolute and relative power of each frequency band per time segment and mean values over the entire recording of 11 minutes. Third, the changes of the mean pupillary diameter per data window against time are shown graphically. An additional parameter referring to the pupil's tendency to instability, the Pupillary Unrest Index (PUI), is defined by cumulative changes in pupil size based on mean values of consecutive data sequences. The method has been tested in 165 healthy male volunteers between 35 and 60 years parallel to a self rating scale (Stanford Sleepiness Scale SSS 1 – 7). Results: The pupillography system applied here offered a stable and reliable long time recording of pupil size even if the pupil was covered partially (up to 50%) by the eyelid. In only one of 165 cases the measurement had to be discarded because of too many artifacts. In all others the average pupillary instability was low, only few pupillary oscillations were seen. Healthy subjects who assigned themselves a value of 1 or 2 at the SSS (highest levels of wakefulness, n=54) showed much less pupillary instability than those who felt sleepy (SSS 4-6, n=14). The remaining subjects assigned themselves as ”indifferent” (SSS 3, n=96). They showed values between both groups but closer to the SSS 1/2 group. The specificity and sensitivity for subjective sleepiness and wakefulness in healthy subjects was 84%. There was a significant correlation between self rating results and pupillary measures. Conclusion: Fatigue waves have a high specificity and sensitivity for daytime sleepiness. Specially designed pupillographic procedures are necessary for stable long time recording and quantitative data evaluation. Given this, pupillography is a reliable tool to measure sleepiness objectively.
Supported by fortuene F. 1222074.1 supported by (DFG) Deutsche Forschungsgemeinschaft WI 1066/3-1

Holger Lüdtke, Constantin Kriegbaum, Beate Leo-Kottler, Helmut Wilhelm
University Eye Hospital Tübingen, Dept. of Pathophysiology of Vision and Neuro-ophthalmology

Pupillary Light Reflexes In Patients With Leber's Hereditary Optic Neuropathy (Lhon)

Purpose. There have been several reports about unusual pupillary behaviour in LHON. Unilateral cases (between involvement of the first and second eye) without relative afferent pupillary defect have been discussed in the NANOS net. According to a pupillographic study* LHON patients show the same pupillary behaviour as normals. Because this fact would raise many questions concerning the real nature of LHON and challenge our concept about the afferent pupillary system, we tried to verify these results. Methods. Pupillary function was assessed in 34 normal subjects (31.7 ± 8.2 years) and 40 patients (33.0 ± 13.3 years) with LHON. Pupillary light reflexes were recorded by means of the Compact Integrated Pupillograph (CIP by AMTech). Time resolution was 5 ms, spatial resolution higher than 0.02 mm. Under mesopic conditions 200 ms stimuli were presented in 2 differenUse of uninitialized value in concatenation (.) or string at E:\listplex\SYSTEM\SCRIPTS\filearea.cgi line 455, line 1598. t stimulus intensities (0.16*103 cd/m2 and 9.80*103 cd/m2). 5 pupillograms were recorded for each eye. Latency, constriction amplitude and baseline diameter were defined automatically. To compare the two groups, for each stimulus an unpaired t-test was applied. Results. For both stimuli there were significant differences in latency between LHON patients and controls (bright stimulus: p<0.001; dark stimulus: p<0.01). The latency proved to be about 10% longer for LHON. The amplitude was significantly smaller in LHON for the bright stimulus (p<0.05). Discussion. Latency time is the most stable parameter of the pupillary light reflex because it shows least variability between individuals and different age groups. In LHON latency time is significantly longer and constriction amplitudes are smaller. The results of our study confirm that LHON really is an optic nerve disease and that the pupillary light reflexes are not normal. Wakakura et al. used relative constriction amplitudes as the only parameter and disregarded all other pupillogram parameters.

* Reference: Wakakura M, Yokoe J. Evidence for preserved direct pupillary light response in Leber's hereditary optic neuropathy. Br J Ophthalmol 1995;79:442-446.