Spectral sensitivity of the photointrinsic iris in the red-eared slider turtle (Trachemys scripta elegans)

Our goal in this study was to examine the red-eared slider turtle for a photomechanical response (PMR) and define its spectral sensitivity. Pupils of enucleated eyes constricted to light by ∼11%, which was one-third the response measured in alert behaving turtles at ∼33%. Rates of constriction in enucleated eyes that were measured by time constants (1.44-3.70 min) were similar to those measured in turtles at 1.97 min. Dilation recovery rates during dark adaptation for enucleated eyes were predicted using line equations and computed times for reaching maximum sizes between 26 and 44 min. Times were comparable to the measures in turtles where maximum pupil size occurred within 40 min and possessed a time constant of 12.78 min. Hill equations were used to derive irradiance threshold values from enucleated hemisected eyes and then plot a spectral sensitivity curve. The analysis of the slopes and maximum responses revealed contribution from at least two different photopigments, one with a peak at 410 nm and another with a peak at 480 nm. Fits by template equations suggest that contractions are triggered by multiple photopigments in the iris including an opsin-based visual pigment and some other novel photopigment, or a cryptochrome with an absorbance spectrum significantly different from that used in our model. In addition to being regulated by retinal feedback via parasympathetic nervous pathways, the results support that the iris musculature is photointrinsically responsive. In the turtle, the control of its direct pupillary light response (dPLR) includes photoreceptive mechanisms occurring both in its iris and in its retina.     

Der Einfluss von Latanoprost 0,005% auf die Pupillenreaktion des menschlichen Auges

PURPOSE: Infrared pupillography was performed to investigate the effect of one week topical treatment with the prostaglandin analogue Latanoprost 0.005% on pupillary reflex to light stimuli in glaucomatous human eyes. METHODS: Infrared pupillography using the compact integrated pupillograph was performed in 20 glaucomatous eyes of 11 patients. After 10 minutes dark adaptation one pupil was stimulated with a blue, yellow and white diode light of 100 ms duration. Measurements of pupil diameter, constriction latency, constriction amplitude and relative constriction amplitude were taken twice for each light source in a time interval of 15 seconds. After a 2 week wash-out period the measurements were performed from 8:00 to 10:00 a.m. before and one week after topical treatment with Latanoprost 0.005% applied as single dose once in the evening. RESULTS: The measurements after 1 week treatment with Latanoprost showed a significantly smaller pupil diameter for blue (p = 0.044) and white stimulus (p = 0.039) and the latency was significantly reduced (p = 0.029) as well. CONCLUSIONS: Although the statistical analysis shows some small significant differences in pupil diameter and constriction latency there were no clinical signs of changes in pupillary response due to Latanoprost. The system turned out as easy to use and showed reliable measurements during the study. How far latanoprost may lead to miosis and a decrease of constriction latency has to be investigated in further studies with larger study populations. Other topics concerning drug influence, diurnal rhythm and glaucomatous damage in pupillary light reaction will be investigated in the near future.     

Changes in corneal DC-potentials associated with changes in pupillary diameter

Using light-emitting diodes we stimulated monocularly with light intensities of between 7.5 and 1,800 cd/m², and recorded simultaneously the Dc-electroretinogram and pupillary movements of the stimulated and the contralateral eye. In some investigations, the visual evoked potential and the activity from the periorbicular muscles were also recorded. Various drugs acting on the autonomous nervous system were topically applied and their effects studied.In the eye with an untreated pupil, stimulated or contralateral, a corneo positive potential coincident with pupillary constriction was seen (c_u-wave), provided the pupil was large before constriction began. However, if the pupil was narrow beforehand, a corneonegative deflection dominated, which was also coincident with pupillary constriction (m_u-wave). Parasympathicolytics or -mimetics abolished both the c_u and m_u-wave.We conclude that the c_u-wave is related to depolarization of the sphincter pupillae during constriction, whereas the m_u-wave might be related to a modification of the potential distribution between the pigment epithelium and the tissue surrounding the eye in the case where the pupil is constricted beyond a critical point.Supported by the Swiss National Science Foundation     

Natural accommodation in the growing chicken

A new technique, Infrared Photoretinoscopy, has been employed for recording natural accommodation in the chicken. The illumination of the pupil by the fundus reflection of infrared light provided by high output light emitting diodes (I.R. LED's) was monitored on a video screen. The defocus of the eye could be calculated by evaluating the fraction of the pupil which was illuminated. It was found that: in the chick the full range of accommodation (about 17D) is present in the first day after hatching, accommodation acts completely independently in both eyes, the "near pupillary response" is weaker in younger chicks, the pupil constriction in response to light starts at higher luminance in the younger chicks the developmental decrease of the f/number is not sufficient to explain the change of the pupil reaction to light. Problems resulting from the use of drugs in order to measure the refractive state using normal retinoscopy are discussed.     

Untersuchungen über den galvanischen Pupillenreflex beim Menschen

Zusammenfassung Die Arbeit befaßt sich, mit der elektrisch ausgelösten Pupillenverengerung (galvanischer Pupillenreflex) beim Menschen. Der Reizstrom wurde meistens über eine kleine (differente) Stirnelektrode und zwei große Unterarmelektroden zugeführt. Die Versuche führte der Verfasser (28 Jahre) im Selbstversuch durch.Ein Versuch mit einer durch Atropin erweiterten Pupille ergab, daß die elektrisch ausgelöste Pupillenverengerung (Gipfelwert etwa 1 mm bei 1,5 mA Reizimpulsamplitude und 20 ms Reizimpulsdauer) nicht durch direkte Reizung des Sphincter pupillae hervorgerufen wird. Ferner läßt sich aus diesem Atropin-Versuch schließen, daß der Dilatator pupillae weder direkt noch indirekt gereizt wird. (Gipfelwert: Maximale Verkleinerung des Pupillendurchmessers infolge des Reizes.)Reizt man nur ein Auge elektrisch (um sicher zu sein, daß nur ein Auge gereizt wird, wurde das gereizte Auge druckblind gemacht), so wird auch am anderen, ungereizten Auge, sehr wahrscheinlich durch Reizung der Retina, eine Pupillenverengerung ausgelöst.Die Latenzzeit der elektrisch ausgelösten Pupillenverengerung (Gipfelwert 0,91 mm) beträgt 266 ms. Sie ist um 62 ms kürzer als die Latenzzeit der durch adäquate Reizung ausgelösten Pupillenverengerung (Gipfelwert 0,92 mm).Die Chronaxie der elektrisch ausgelösten Pupillenverengerung und die Chronaxie des gleichzeitig beobachtbaren Phosphens beträgt etwa 9,3 ms.

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Summary The paper is dealing with the electrically released pupillary constriction (galvanic pupillary reflex) in man. The stimulating current was mostly supplied by a small (different) forehead electrode and two big forearm electrodes. The experiments were made by the author himself (28 years) in measuring one of his own pupils.An experiment with a pupil dilated by atropine showed that the electrically released constriction of the pupil (peak value about 1 mm at 1.5 ma amplitude of the stimulating pulse and 20 ms duration of the stimulating pulse) is not caused by direct stimulation of the sphincter of the pupil. Furthermore, from this atropine-experiment it can be concluded that the dilatator of the pupil is not stimulated either directly or indirectly (peak value: maximum reduction of the pupillary diameter as a result of the stimulus).If only one eye is stimulated electrically (to make sure that only one eye is stimulated, the stimulated eye was made pressure-blind) a pupillary constriction is also released, most probably by stimulating the retina, on the other unstimulated eye.The latency period of the electrically released pupillary constriction (peak value 0.91 mm) is 266 ms. This latency period is 62 ms shorter than the latency period of the pupillary constriction (peak value 0.92 mm) which is caused by adequate stimulation.The chronaxy of the electrically released pupillary constriction and the chronaxy of the simultaneously visible phosphene is about 9.3 ms.

     

Tonic pupil and Czarnecki's sign following third nerve palsy.

A 71-year-old woman developed abnormal pupillary function in one eye after a third nerve palsy. Stimulation with light caused segmental constriction of the pupil, the near reflex was normal, and gaze upward elicited constriction of portions of the sphincter that were unreactive to light. This combination of findings has not been reported previously. We believe that this case supports the idea that a tonic pupil can be caused by aberrant reinnervation of the ciliary ganglion.     

Portable pupillography of the swinging flashlight test to detect afferent pupillary defects

OBJECTIVE: To investigate the ability of a portable, personal computer-driven, pupillometer to record the pupillary response curve during the swinging flashlight test. Also, to determine whether these response curves can be used to identify and quantify relative asymmetry in the pupillary light reflex between eyes in healthy volunteers with simulated afferent pupil defects (APDs) and patients with optic neuropathies. DESIGN: Comparative, observational case series and instrument validation. PARTICIPANTS: Healthy volunteers with no known ocular disease and patients (n = 20) with various optic neuropathies noted to have relative APDs on examination. METHODS: Pupillary response curves of the right eye were recorded with a portable, electronic, infrared pupillometer from healthy volunteers (with and without simulated APDs) and patients with APDs while the light stimulus alternated between eyes, simulating the swinging flashlight test. Simulated APDs in healthy volunteers were created with increasingly dense neutral density filters in front of the left eye. MAIN OUTCOME MEASURES: Differences in constriction amplitude, latency, and constriction velocity of the pupillary response with right eye stimulation versus left eye stimulation in both groups of subjects. RESULTS: A significant correlation between neutral density filter strength and intereye differences was seen for all measurement parameters in volunteers with simulated APDs. Depending on the measurement parameter and stimulus intensity, simulated APDs of 0.6 log units or more could be distinguished from normal responses. Clinically graded true APDs had intereye differences similar to simulated APDs of the same density. Those with real and simulated APDs of 0.9 log units or more could be distinguished from healthy volunteers with 80% sensitivity and 92% specificity. Responses from those with real and simulated small APDs of 0.3 to 0.6 log units could not be distinguished reliably. CONCLUSIONS: Portable, personal-computer driven, electronic, infrared pupillography can record the swinging flashlight test accurately and identify large afferent pupillary defects. An affordable, portable, reliable device for identifying relative APDs would be useful in the identification and follow-up of patients with neurogenic vision loss.     

Effects of unilateral topical atropine on binocular pupil responses and eye growth in mice

Purpose

Studies on drugs selected to target myopia development often use the vehicle-treated fellow eye as a control. However, it is not clear how much of the drug reaches the fellow eye, rendering it a potentially invalid control. Therefore, in this study, pupil responses were used to probe the effects of atropine in both eyes in mice, after unilateral topical application. In a second experiment, interocular differences in refractive development and axial eye growth were studied while atropine was applied daily to one eye.

Methods

In 20 C57BL/6 (B6) wildtype mice, a single drop of 1% atropine solution was instilled into one eye. Mice were gently restrained by holding their necks while video image processing software detected the pupil and measured its diameter at a sampling rate of 30 Hz. A bright green LED, attached to the photoretinoscope of the video camera, was flashed. Pupil responses were quantified daily over a period of 2 weeks. In another group of 24 mice, one drop of 1% atropine was applied daily for 28 days. Axial length was measured pre- and post-treatment, using low coherence interferometry (the Zeiss AC-Master). Refractive development was measured by infrared photorefraction.

Results

Similar to previous findings with the same device, untreated eyes displayed a pupil constriction of 24.84 ± 1.73% upon stimulation with the green LED. A single drop of 1% atropine caused complete suppression with no significant recovery over the whole observation period of two weeks. The responses in the fellow eye were temporarily reduced to about 75% and then recovered towards baseline. After daily atropine application, there was significant reduction in axial length of the eyes, relative to the saline-treated fellow eyes (3.234 ± 0.186 versus 3.378 ± 0.176 mm, n = 24, p < 0.01, paired t-test) and the refractions became more hyperopic/less myopic (+13.46 ± 2.15 D versus +10.06 ± 2.02 D, n = 24, p < 0.01).

Conclusions

In line with previous findings, one drop of atropine solution caused a long lasting suppression of pupil responses in the mouse eye. New data show that the transfer to the fellow eye was limited, making interocular comparisons feasible. It is also new that topical atropine reduced axial eye growth even when mice had largely normal vision.     

The role of the pupil light reflex in aiding adaptation to the dark.

Various proposals for the function of the pupillary light reflex are discussed in quantitative terms. Two proposals are examined experimentally. It is suggested that the major purpose of pupillary constriction to light is to reduce retinal illumination and prepare the eye for a return to darkness. A mobile pupil (as opposed to a fixed) produces a substantial improvement in stimulus detection during the first few minutes of dark adaptation.     

Pupillary micro movements apparently related to pulse frequency

Pupillary micro changes in diameter apparently related to pulse frequency are superimposed on the larger fluctuations called the pupillary unrest. This small component of the pupillary unrest waxes and wanes with each pulsation of the blood. The effect was found to vary inversely with the average pupil diameter which can be controlled by making the eye accommodate or allowing more or less light to enter the eye.     

Pupillary response to four concentrations of pilocarpine in normal subjects: application to testing for Adie tonic pupil

PURPOSE: To determine the amount of pupillary constriction to four different concentrations of pilocarpine in normal human subjects and to determine if pupillary constriction correlates with bioavailability of the instilled concentrations. The amount of pupillary constriction to dilute pilocarpine is utilized as a diagnostic test for Adie tonic pupil as distinguished from a normal pupil response. DESIGN: Twenty healthy volunteers had automated binocular infrared pupillography in the dark after instillation of four different concentrations of dilute pilocarpine. Ocular penetration of eye drops was also assessed using 2% fluorescein sodium as a tracer. METHODS: Prospective institutional double-masked study of both eyes of twenty healthy volunteers, ten with brown irides, ten with blue irides, between the ages of 20-40 years. RESULTS: A pilocarpine dose-dependent curve showed decreased pupil size within 15 minutes, peaking at 30-60 minutes. No difference was noted between right and left eyes, iris color, or corneal permeability. CONCLUSIONS: Normal pupils constrict to dilute concentrations of pilocarpine (0.25% or 0.125%), but constrict insignificantly to concentrations of 0.0313% or 0.0625%. Pupil constriction with 0.0625% pilocarpine should distinguish an Adie pupil from normal. This confirms the utility of this simple office diagnostic procedure.     

Dark adaptation during transient hyperglycemia in type 2 diabetes

It was the purpose of the present study to examine dark adaptation in subjects with type 2 diabetes during transient hyperglycemia. Twenty-four subjects with type 2 diabetes and minimal diabetic retinopathy were randomized to undergo an oral glucose tolerance test (OGTT) or to remain fasting. Dark adaptometry was measured in one eye, chosen at random, using a computer-controlled dark adaptometer. Dark adaptation and capillary blood glucose were measured at baseline and 80 minutes into the OGTT/fasting test. Blood glucose remained stable throughout the examination in the 12 fasting subjects, whereas glycemia increased in the 12 OGTT subjects, from 8.6 ± 2.1 at baseline to 21.1 ± 3.6 mM after 80 min. In the OGTT group, four out of seven subjects with delayed dark adaptation at baseline reached normal values during hyperglycemia. All examined aspects of rod adaptation were accelerated by hyperglycemia (time to rod-cone break −26%; time to rod intercept −16%, rod sensitivity recovery slope (log units/min) +35%), whereas no measurable change in cone adaptation was seen. The results are consistent with rod adaptation being limited by glycemia and with rod adaptation being delayed in subjects with diabetes compared with healthy subjects, the delay being reversible in response to hyperglycemia.     

Ideal concentration of tropicamide with hydroxyamphetamine 1% for routine pupillary dilation

In this double-masked clinical study, we evaluated four concentrations of tropicamide (0.05%, 0.1%, 0.25%, and 0.5%) combined with hydroxyamphetamine 1% to find the combination that gives maximal pupillary dilation and inhibition of responsiveness to light and minimal paralysis of accommodation. With all concentrations, pupil size was maximal at 60 minutes, and there was no significant difference between the groups in mean pupillary diameter. Inhibition of the pupillary responses to light and loss of accommodation were directly related to the concentration of tropicamide. Tropicamide 0.25% combined with hydroxyamphetamine 1% was considered ideal for dilation and inhibition of the light response without inhibiting accommodation for near vision.     

Beeinflussung der Pupillenreaktion durch Brimonidin

PURPOSE: The effect of brimonidine in comparison with acetazolamide on pupillary reflex was investigated in 18 volunteers.METHODS: Infrared pupillography was performed with white diode light of 200 ms duration to measure pupil diameter, constriction latency, reaction time, constriction amplitude, and relative constriction amplitude. The measurements were performed according to a fixed schedule including a phase without medication to determine the baseline level. Data were analyzed by Student's paired t-test.RESULTS: Application of brimonidine and acetazolamide led to a significantly reduced intraocular pressure as well as static and dynamic differences in the pupillary reflex. The pupil diameter measurements were significantly smaller after both medications in comparison to baseline. The reduction of pupil diameter after brimonidine led to significantly reduced contraction amplitude and prolonged latency.CONCLUSION: Application of brimonidine leads to significant miosis, which might due to the affinity to alpha(2)-receptors with reduction of noradrenaline release in the synapse. This effect may play a role in a higher decrease of intraocular pressure by increasing aqueous humor outflow in comparison to clonidine and apraclonidine, but further investigations are required.     

A technique for estimating the contribution of photomechanical responses to visual adaptation

This paper presents a technique for isolating and quantifying the contribution of photomechanical responses to visual adaptation. The technique is developed in the context of the pupillary mechanism that is active in the primary visual cells of the insect eye. Using a feedback-control model to represent the combination of retinular cell and pupil, it is shown that the effect of pupillary movements on retinal illumination can be inferred by analysing an intensity-response function of the pupil. When the technique is applied to the pupils of the butterfly and the fly, the results indicate that, in each case, the pupil decreases retinal illumination by approximately 0.7 log units when the ambient light level is increased from pupillary threshold to a level 2.5 log units higher. The validity of the technique is examined by applying it to the human pupil. The results predict changes of retinal illumination which are in close agreement with those expected on the basis of changes in iris diameter, including the Stiles-Crawford effect. The procedure presented here is simple and can, in principle, be applied to many forms of photomechanical adaptation.     

Pupillary light reflexes in patients with Leber’s hereditary optic neuropathy

 Background: According to a recent pupillographic study, patients with Leber’s hereditary optic neuropathy (LHON) show the same pupillary behaviour as normals. Because this raises many questions concerning the real nature of LHON and challenges our concept of the afferent pupillary system, we tried to verify the results of this study. · Methods: Pupillary function was assessed in 34 normal subjects and 40 patients with LHON. Pupillary light reflexes were recorded by means of the Compact Integrated Pupillograph (CIP, AMTech). Under mesopic conditions 200-ms stimuli were presented at two different stimulus intensities. Latency, constriction amplitude and baseline diameter were defined automatically. Pupil light reflexes were compared between LHON patients and normals and between the better and the worse eye in 20 LHON patients with different visual acuities. · Results: For both stimuli there were significant differences in latency between LHON patients and controls. The latency of the pupil light reflex proved to be about 20 ms longer for LHON patients, and the amplitude was significantly smaller for the bright stimulus. Within LHON patients, the eyes with the worse visual acuity had a significantly smaller constriction amplitude than the eyes with the better visual acuity. · Conclusion: The results of our study confirm that LHON really is an optic nerve disease and that the pupillary light reflexes are not normal. Received: 5 January 1998 Revised version received: 28 February 1998 Accepted: 11 March 1998     

The pupillary light reflex in normal and innate microstrabismic cats, I: Behavior and receptive-field analysis in the nucleus praetectalis olivaris

Neurons in the nucleus praetectalis olivaris (NPO) were antidromically identified by electrical stimulation of the nucleus of Edinger-Westphal (EW), the location of preganglionic pupilloconstrictor motoneurons. Electrical stimulation within the NPO leads to bilateral pupil constriction. Single neurons recorded in the NPO respond tonically to light stimuli, and their discharge frequency increases linearly with logarithmic increase in light intensity. This characteristic identifies NPO neurons as luminance detectors. They have large receptive fields mostly lying in the upper and contralateral quadrant of the visual field. Cats with impaired binocular vision show a significantly reduced binocular summation of the pupillary light reflex (BSP), i.e. the increase of pupil constriction during binocular illumination when compared to monocular illumination is less than in normal animals. The investigation of ocular dominance and subthreshold binocular interactions in the NPO of normal and innate microstrabismic cats revealed two possible mechanisms for BSP and its reduction in strabismic subjects. First, the percentage of neurons increasing their discharge rate by illuminating either eye is significantly reduced in the NPO of innate microstrabismic cats (6.6%) when compared to normal cats (22% of all neurons tested). Second, in most NPO neurons of normal cats the subthreshold influence of the ipsilateral eye leads to an increase in neuronal activity during binocular stimulation when compared to monocular stimulation of the contralateral eye (binocular summation). The subthreshold influence of the ipsilateral eye in most NPO neurons of microstrabismic cats, however, is inhibitory, i.e. the neuronal discharge rate during binocular stimulation is decreased when compared to monocular stimulation of the contralateral eye (binocular inhibition). However, there is no significant correlation between BSP and binocularity in the NPO in individual animals. This suggests that BSP may be additionally influenced by visual structures other than NPO.     

Kestenbaum's number as an indicator of pupillomotor input asymmetry

We compared the direct light response of both eyes in 90 patients who had anterior visual pathway disease using two different testing methods. We measured Kestenbaum's number in millimeters of pupillary diameter. Kestenbaum's number (K) is the difference in the pupil size attained in each eye under direct illumination while the other eye is occluded. We then measured the relative afferent pupillary defect (RAPD) in log units using neutral density filters. The two tests gave similar results (K = 0.88 x RAPD). Kestenbaum's number is the less precise measure, but it can be quickly and cheaply estimated even in dark brown eyes. The filter test requires a set of filters and at least one well-innervated iris sphincter. Kestenbaum's number can be measured without filters, but the iris sphincter and dilator muscles in both eyes must be normally innervated.     

虹膜松驰综合征两种处理方式的对比研究

目的比较前房内注入肾上腺素联合利多卡因和应用瞳孔扩张器两种方式处置虹膜松驰综合征（IFIS）的有效性。方法 43例（43只眼）发生IFIS患者中,25例采用前房内注入0.1%肾上腺素联合0.5%利多卡因处置,18例采用瞳孔扩张器处置,观察虹膜涌动、瞳孔缩小及虹膜脱出的改善程度。结果 25例IFIS患者采用前房内注入0.1%肾上腺素联合0.5%利多卡因处置,仅9例（36.0%）恢复瞳孔扩张状态,其中11例虹膜脱出者中仅2例（18.2%）未再发生虹膜脱出;18例IFIS患者采用瞳孔扩张器处置,均恢复瞳孔扩张状态（100.0%）,其中8例虹膜脱出者仅1例（12.5%）术中未再发生虹膜脱出。结论前房内注入肾上腺素联合利多卡因不能有效阻止IFIS的发生,对手术操作帮助不大;瞳孔扩张器能有效阻止虹膜涌动及瞳孔缩小,降低手术难度,但不能有效防止虹膜脱出,应特别注意。