Light-induced Pupil Research Articles

A High-Precision Real-Time System for Pupil Size Measurement using an Infrared Camera and LED Light Stimulation

This research is dedicated to the exploration of sophisticated methodologies and the creation of a high-precision system for pupil size measurement that is capable of displaying real-time results. The comprehensive system encompasses an infrared camera, an infrared LED light, an LED light box designed for pupil stimulation, and robust control software that enables analysis, measurement, and real-time documentation of results. Our study yielded promising results with a high degree of precision in pupil size measurements, thereby opening new possibilities for intricate vision-related research and applications. With its potential impact, the system can offer profound contributions to areas including eye-health diagnosis, human-computer interaction research, and studies focusing on light-induced pupil response.

Pupillary Light Reflex Correction for Robust Pupillometry in Virtual Reality

Virtual reality (VR) headsets with an integrated eye tracker enable the measurement of pupil size fluctuations correlated with cognition during a VR experience. We present a method to correct for the light-induced pupil size changes, otherwise masking the more subtle cognitively-driven effects, such as cognitive load and emotional state. We explore multiple calibration sequences to find individual mapping functions relating the luminance to pupil dilation that can be employed in real-time during a VR experience. The resulting mapping functions are evaluated in a VR-based n-back task and in free exploration of a six-degrees-of-freedom VR scene. Our results show estimating luminance from a weighted average of the fixation area and the background yields the best performance. Calibration sequence composed of either solid gray or realistic scene brightness levels shown for 6 s in a pseudo-random order proved most robust.

Melatonin Prevents Non-image-Forming Visual System Alterations Induced by Experimental Glaucoma in Rats.

Glaucoma is a blindness-causing disease that involves selective damage to retinal ganglion cells (RGCs) and their axons. A subset of RGCs expressing the photopigment melanopsin regulates non-image-forming visual system functions, such as pupillary light reflex and circadian rhythms. We analyzed the effect of melatonin on the non-image-forming visual system alterations induced by experimental glaucoma. For this purpose, male Wistar rats were weekly injected with vehicle or chondroitin sulfate into the eye anterior chamber. The non-image-forming visual system was analyzed in terms of (1) melanopsin-expressing RGC number, (2) anterograde transport from the retina to the olivary pretectal nucleus and the suprachiasmatic nuclei, (3) blue- and white light-induced pupillary light reflex, (4) light-induced c-Fos expression in the suprachiasmatic nuclei, (5) daily rhythm of locomotor activity, and (6) mitochondria in melanopsin-expressing RGC cells. Melatonin prevented the effect of experimental glaucoma on melanopsin-expressing RGC number, blue- and white light-induced pupil constriction, retina-olivary pretectal nucleus, and retina- suprachiasmatic nuclei communication, light-induced c-Fos expression in the suprachiasmatic nuclei, and alterations in the locomotor activity daily rhythm. In addition, melatonin prevented the effect of glaucoma on melanopsin-expressing RGC mitochondrial alterations. These results support that melatonin protected the non-image-forming visual system against glaucoma, probably through a mitochondrial protective mechanism.

Vault Changes Caused by Light-Induced Pupil Constriction and Accommodation in Eyes With an Implantable Collamer Lens.

Purpose:An appropriate vault after implantation of a posterior chamber phakic intraocular lens with a central hole (ICL KS-AP) is important for successful long-term outcomes. In the present study, we used anterior segment optical coherence tomography (AS-OCT) to examine dynamic pupil and vault changes under photopic and scotopic conditions and during accommodation in eyes with ICL KS-AP.Methods:This retrospective study included patients at an outpatient ophthalmology clinic who underwent ICL KS-AP implantation >1 month before enrollment. All patients underwent dynamic AS-OCT imaging under photopic and scotopic conditions. Patients aged <40 years also underwent imaging in the accommodative and nonaccommodative states. Primary outcome measures were the pupil size and vault at the maximum and minimum pupil sizes.Results:This study included 91 eyes of 47 patients (35.5 ± 8.6 years, 21 men). Accommodation was examined in 51 eyes of 26 patients (28.9 ± 5.0 years, 10 men) younger than 40 years. The pupil size was significantly smaller under photopic conditions (3.64 ± 0.77 mm) than under scotopic conditions (4.91 ± 0.75 mm, P < 0.001) and during accommodation (3.88 ± 0.64 vs. 4.10 ± 0.61 mm, P < 0.001). Vault was also significantly lower under photopic conditions (476.1 ± 219.6 μm) than under scotopic conditions (521.1 ± 220.4 μm, P < 0.001) and during accommodation (454.8 ± 224.9 vs. 481.6 ± 219.1 μm, P < 0.001).Conclusions:Vault can be significantly lowered by light-induced pupil constriction and accommodation in eyes with ICL KS-AP.

New Findings for an Old Disease

To review our previous studies regarding the morphology of the cornea in pseudoexfoliation syndrome (PEX) and anatomical discrepancies between PEX and contralateral eyes in unilateral PEX. We used in vivo confocal microscopy to observe the corneas of PEX, contralateral, and normal control eyes. Morphological alterations correlated with the corneal sensitivity of the eyes with PEX. Anterior segment optical coherence tomography was used to study patients diagnosed with unilateral PEX. Dynamic dark-light changes of the anterior chamber angle and iris were captured by anterior segment optical coherence tomography real-time video recording. Anterior chamber angle parameters and iridolenticular contact distance were analyzed. The result of a national survey on the etiology of bullous keratopathy is presented. Corneal cell density was decreased in PEX eyes compared with that of normal control eyes. The density of the subbasal nerve plexus was significantly decreased but with increased tortuosity. Morphological changes correlated with decreased corneal sensitivity. Contralateral PEX eyes shared similar morphological changes with PEX eyes. Eyes with PEX had a significantly shallower anterior chamber and decreased angle openness during light-induced pupil constriction. The iridolenticular contact distance was significantly greater in PEX eyes than in contralateral eyes. A Japanese national survey demonstrated the increased incidence of PEX endotheliopathy as the cause of unknown bullous keratopathy. PEX keratopathy involves all layers of the cornea. Morphological changes of the anterior chamber may contribute to PEX progression. Contralateral eyes were at preclinical stages of the PEX process. PEX endotheliopathy accounts for an increased incidence of bullous keratopathy, especially in a country with a large aged population, such as Japan.

Dose-Dependent Effects of Androgens on the Circadian Timing System and Its Response to Light

The hypothalamic suprachiasmatic nucleus (SCN) is the locus of a master clock that regulates circadian rhythms in physiology and behavior. Gonadectomy in male mice lengthens the period of circadian rhythms and increases the day-to-day variability of activity onset time. Both of these responses are rescued by the nonaromatizable androgen dihydrotestosterone. Androgen receptors (AR) are localized in SCN neurons that receive direct retinal input. To explore how androgens affect circadian clock function and its responsiveness to photic cues, we measured wheel-running behavior and SCN AR expression in intact, gonadectomized, and testosterone-replaced mice, held under various photic conditions. Gonadectomy lengthened circadian period in constant dim light but not in constant darkness. Increasing intensities of constant light parametrically increased circadian period, and this was potentiated at all intensities by gonadectomy. In contrast, gonadectomy did not alter light-induced pupil constriction, suggesting a nonretinal locus of hormone action. In hormone-replaced animals housed in constant darkness, T concentration was positively correlated with precision of activity onset and with SCN AR expression and negatively correlated with duration of activity. We infer the existence of two androgenic mechanisms: one modulates SCN responsiveness to light, and the second modulates SCN timekeeping and locomotor activity in a dose-dependent manner. Finally, the effects of androgens on period are a result of hormonal modulation of the SCN's response to photic input rather than to a change in the inherent period of oscillators in the absence of light.

Akkommodationsmechanismus am jungen menschlichen Auge - einige neue Aspekte

The basics of the model of accommodation were described by Hermann von Helmholtz 150 years ago and are accepted until today. Twenty-five healthy young phakic test persons (age range 14 to 28 years) were examined using the IOL Master (Carl Zeiss Jena GmbH), slit lamp photography (Scheimpflug camera EAS 1000, Nidek) and pupillography (AMTech GmbH). Measurements were taken of disaccommodated and accommodated eyes. The mesopic and photopic pupil size are statistically significant (p < 0.05) smaller in accommodated eyes than in disaccommodated. Also, a significantly shorter reaction time of the light-induced pupil reaction with accommodation could be shown compared to disaccommodation. The central vertical and horizontal radii of curvature of the cornea increased with accommodation. This is likewise a decrease of the central anterior corneal curvature by near fixation. Due to the axial lens thickening, the anterior chamber angle and the anterior chamber depth decreased. Consequently, a decrease of the lens transparence resulted with accommodation. As a result of our measurements the existing model of accommodation, developed by Hermann von Helmholtz 150 years ago, can be modified.

Pupillographic Evaluation of the Time Course of Atropine Effects in the Mouse Eye

The nonselective muscarinic antagonist atropine is currently the most potent drug against myopia development in both humans and animal models. However, the mechanism by which myopia is suppressed is still unknown, and the time course of its action is not well documented. Therefore, we have studied the duration of mydriasis in the mouse, a new model of myopia, after topical application of a single eye drop with different doses of atropine. The light-induced pupil response of the C57BL/6 (B6) wildtype strain was studied in alert mice that were restrained by grasping their necks. A video image-processing program detected the pupil and measured its diameter at 25 Hz sampling rate. To stimulate, an arrangement of green LEDs, which was attached to the recording video camera, could be flashed for 40 ms by pressing a key on the keyboard. A single drop of atropine solution (1, 0.5, or 0.1%) was instilled in one eye and the recovery of the pupil responses was followed for at least 150 h. Both eyes were measured. 1) Under the defined stimulation conditions, untreated wildtype mice displayed a pupil constriction of 23.7 +/- 2.4%. 2) All doses of atropine caused complete suppression of the pupil responses in the treated eyes within 1 min. 3) The pupil responses of the fellow eyes remained unaffected and were not different from those in untreated animals. 4) The recovery from mydriasis was very slow and did not show clear differences with dose. The extrapolated duration of complete recovery was about 10 d (0.1%: 217 h; 0.5%: 230 h; 1%: 294 h). Atropine caused a longlasting suppression of the pupil responses in the mouse eye. That the duration of recovery was not obviously dose-dependent suggests that all doses used in this study were saturating the receptors in the iris musculature.

Pupil cycle induction test: a way of evaluating the pupillary light reflex.

The Pupil Cycle Induction Test (PCIT) described here is a simple and sensitive clinical method for the evaluation of afferent pupillary defect. It assesses the difficulty in setting up regular and sustained light-induced pupil oscillations, in contrast to methods assessing the light reflex by timing the oscillations. PCIT was applied to 186 presumably normal eyes (with normal visual acuity and normal fundi). In ten eyes, sustained oscillations could not be induced; further investigation showed that four of these eyes had altered visual-evoked response. The test was also carried out in 34 patients suffering from anterior visual pathway disorders. Sustained pupil oscillations could not be set up in 44 out of the 57 affected eyes. In the present series, significant alteration of light-induced pupil oscillations has been observed in several patterns: (1) immediate alteration; (2) delayed interruption of oscillations without spontaneous recovery, and (3) intermittent periods with oscillations of relatively small amplitude lasting more than three pupil cycles. PCIT assesses changes in light threshold for pupil response. It is suggested that delayed and transient alterations of oscillations are related to time-dependent afferent pupil defects similar to intermittent abnormalities of visual function reported in patients with diseases of the optic nerve or the chiasm.