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The timecourse and extent of changes in pupil area in response to light are reviewed in all classes of vertebrate and cephalopods. Although the speed and extent of these responses vary, most species, except the majority of teleost fish, show extensive changes in pupil area related to light exposure. The neuromuscular pathways underlying light-evoked pupil constriction are described and found to be relatively conserved, although the precise autonomic mechanisms differ somewhat between species. In mammals, illumination of only one eye is known to cause constriction in the unilluminated pupil. Such consensual responses occur widely in other animals too, and their function and relation to decussation of the visual pathway is considered. Intrinsic photosensitivity of the iris muscles has long been known in amphibia, but is in fact widespread in other animals. The functions of changes in pupil area are considered. In the majority of species, changes in pupil area serve to balance the conflicting demands of high spatial acuity and increased sensitivity in different light levels. In the few teleosts in which pupil movements occur they do not serve a visual function but play a role in camouflaging the eye of bottom-dwelling species. The occurrence and functions of the light-independent changes in pupil size displayed by many animals are also considered. Finally, the significance of the variations in pupil shape, ranging from circular to various orientations of slits, ovals, and other shapes, is discussed., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Purpose: To study the effect of the internal fixation lamp on anterior chamber width measured by anterior segment optical coherence tomography., Methods: In a prospective cross sectional observational study, consecutive 22 right eyes of 22 patients (4 men and 18 women) with suspected primary angle closure underwent swept source domain anterior segment optical coherence tomography (AS-OCT), (CASIA SS-1000, Tomey, Nagoya, Japan). Anterior chamber parameters of angle opening distance (AOD), trabecular-iris angle (TIA), angle recess area (ARA) at 500 or 750 µm from scleral spur and pupil diameter were measured by AS-OCT in a three-dimensional mode in 4 quadrants (superior, inferior, temporal and nasal) in dark room setting both with and without internal fixation lamp., Results: Anterior segment parameters of AOD 500 in superior, inferior and temporal quadrants, AOD 750 at superior and nasal, TIA 500 at superior, and inferior and TIA 750 at superior and nasal, and ARA 500 or 750 at superior and inferior with internal fixation lamp were greater and the pupil diameter was significantly (all P < 0.05, paired t test) smaller than when measured without fixation lamp., Conclusions: Internal fixation lamp of the anterior segment OCT makes the pupil constrict and angle wider. When using AS-OCT with usual setting with internal fixation lamp on with eyes in which the anterior chamber angle is narrow but open, it is recommended that the internal fixation lamp be turned off to ensure a clear indication as to whether the angle is open or closed in the dark.

Purpose: We estimate and compare change in iris cross-sectional area (IA) after physiologic and pharmacologic mydriasis in subjects with different dominant mechanisms for primary angle closure., Methods: Anterior segment optical coherence tomography (AS-OCT) measurements in light, dark, and following pharmacologic dilation were obtained on primary angle closure suspects (PACS), primary angle closure (PAC), and primary angle closure glaucoma (PACG) examined during the 5-year follow-up of the Handan Eye Study. Subjects were categorized into three subgroups according to their dominant angle closure (AC) mechanisms as determined by AS-OCT: pupillary block (PB), plateau iris configuration (PIC), and thick peripheral iris roll (TPIR). The IA and other biometric parameters measured using the Zhongshan Angle Assessment Program in the right eyes of all subjects were analyzed., Results: A total of 364 right eyes of subjects with PACS (333), and PAC/PACG (31) was included in the analysis. Significant differences in the change of IAs (P = 0.030), IA loss per mm pupil diameter (PD) increase (P = 0.001) in light versus pharmacologic dilation, and IA loss per mm PD increase (P = 0.011) from dark versus pharmacologic dilation were observed among the three groups. The smallest decrease occurred in the PB group., Conclusions: There are significant differences in IA and IA loss per mm of pupil change following physiologic or pharmacologic mydriasis in Chinese subjects with dissimilar dominant mechanisms for AC. Dynamic iris change may have a more important role in angle closure where PB is the dominant mechanism., (Copyright 2015 The Association for Research in Vision and Ophthalmology, Inc.)

Purpose: To determine the photopic pupil diameter and its determinants in a sample derived from a population-based survey in Tehran., Methods: In a cross-sectional study with a stratified random cluster sampling approach, 410 people age 14 years and over were selected from those residing in the first four municipality districts of Tehran after applying exclusion criteria, and 800 eyes (399 right eyes and 401 left eyes) were examined with the Orbscan II. The main outcome measure was the mean pupil diameter under photopic conditions, and possible correlations with potential determinants were evaluated through linear regression analyses. The design effect of a cluster sampling approach was observed and adjusted for., Results: The mean age of the participants was 40.6 +/- 16.8 years and 38.8% were male. The mean photopic pupil diameter (PPD) was 3.70 mm (range 2.30 to 5.10; 95% confidence interval (CI) 3.62 to 3.78). The mean PPD was 3.67 mm (95% CI, 3.54 to 3.81) in men and 3.72 mm (95% CI, 3.63 to 3.81) in women (p = 0.481). There was a significant reduction of 0.021 mm in PPD per year of aging (r = -0.49, p < 0.001). There was also a significant inverse correlation between PPD and spherical equivalent (r = -0.12, p = 0.034), while there was 0.66-mm increase in PPD with every 1.0-mm increase in the anterior chamber depth (ACD) (p < 0.001). Anisocoria, defined as a pupil diameter difference more than 0.4 mm between two eyes, was observed in 12.2% of the study population., Conclusion: While the mean PPD measured with the Orbscan II was 3.70 mm in a sample derived from a population-based survey in Tehran, the scarcity of similar studies and reports concerning the pupil diameter measured with the Orbscan II makes it difficult to draw eligible comparisons. The pupil diameter has reverse correlations with age and spherical equivalent, a direct correlation with ACD, but is not correlated with gender.

Purpose: This study was conducted to determine the magnitude of pupil center shift between the illumination conditions provided by corneal topography measurement (photopic illuminance) and by Hartmann-Shack aberrometry (mesopic illuminance) and to investigate the importance of this shift when calculating corneal aberrations and for the success of wavefront-guided surgical procedures., Methods: Sixty-two subjects with emmetropia underwent corneal topography and Hartmann-Shack aberrometry. Corneal limbus and pupil edges were detected, and the differences between their respective centers were determined for both procedures. Corneal aberrations were calculated using the pupil centers for corneal topography and for Hartmann-Shack aberrometry. Bland-Altmann plots and paired t-tests were used to analyze the differences between corneal aberrations referenced to the two pupil centers., Results: The mean magnitude (modulus) of the displacement of the pupil with the change of the illumination conditions was 0.21+/-0.11 mm. The effect of this pupillary shift was manifest for coma corneal aberrations for 5-mm pupils, but the two sets of aberrations calculated with the two pupil positions were not significantly different. Sixty-eight percent of the population had differences in coma smaller than 0.05 microm, and only 4% had differences larger than 0.1 microm. Pupil displacement was not large enough to significantly affect other higher-order Zernike modes., Conclusions: Estimated corneal aberrations changed slightly between photopic and mesopic illumination conditions given by corneal topography and Hartmann-Shack aberrometry. However, this systematic pupil shift, according to the published tolerances ranges, is enough to deteriorate the optical quality below the theoretically predicted diffraction limit of wavefront-guided corneal surgery.

Purpose: Contraction anisocoria describes a phenomenon in which the pupil of a directly illuminated eye constricts more than the pupil of the consensual (not illuminated) eye. The purpose of this study was to investigate the lateralization of contraction anisocoria in young female and male subjects., Methods: Infrared binocular pupillography was used to measure pupillary light reflex (PLR) in 44 healthy children (23 girls, 21 boys) from 6 to 16 years of age. Measurements were conducted in both light-adapted and dark-adapted conditions with different stimulus intensities. Relative constriction amplitude was obtained by dividing the maximal pupil area change by the initial static pupil area. Contraction anisocoria was calculated by subtracting relative constriction amplitude in the consensual eye from that of the direct eye. Values of contraction anisocoria obtained by stimulating a subject's right or left eye were compared to determine any potential lateralization., Results: It was found that stimulating the right eye led to larger contraction anisocoria than stimulating the left eye. Such right-side lateralization of contraction anisocoria is much greater in males than in females. In addition, the effects of sex were related to the ambient light level and stimulus intensity., Conclusions: These results provide evidence that contraction anisocoria is more laterally asymmetric in males than in females.

Purpose: To estimate the change in iris cross-sectional (CS) area with pupil dilation using anterior segment optical coherence tomography comparing eyes with angle closure (AC) to open angle glaucoma (OAG)., Methods: Sixty-five patients from the Wilmer Glaucoma service, 36 with definite or suspected OAG and 29 with definite or suspected AC, underwent anterior segment optical coherence tomography imaging under 3 conditions (pupil constriction to light, physiologic dilation in the dark, and after pharmacologic dilation). The nasal and temporal iris CS areas were measured with custom software, 3 times in each of 4 meridians. The principal outcome variables were iris CS area and change in iris CS area/mm pupil diameter change. The relation of these parameters to potential variables that would influence iris area was estimated by multivariate regression., Results: CS area was smaller in eyes with larger pupil diameter, those that had undergone trabeculectomy, and those of European-derived persons (P<0.05 for all in a univariate analysis). In a multivariate model with CS area as the dependent variable, larger pupil diameter (with a 0.19 mm decrease in CS area for each 1 mm of pupil enlargement, P=0.0002), and trabeculectomy remained significant factors. In a second multivariate model, AC irides had less change in CS area/mm pupil enlargement than OAG or OAG suspects (P=0.01). Change in iris CS area was essentially complete in 5 seconds (n=10 eyes)., Conclusions: The iris loses nearly half its volume from a pupil diameter of 3 to 7 mm, probably by eliminating extracellular fluid. Smaller iris CS area change with physiologic pupil dilation is a potential risk factor for AC. Dynamic iris CS area change deserves testing as a prospective indicator of AC.

Purpose: We aimed to evaluate the dynamic function of iris muscle in asymmetric pseudoexfoliation patients by videonystagmography., Methods: 15 patients with asymmetric pseudoexfoliation and 15 control subjects were included. The function of iris muscle was assessed by the pupillometry test of the videonystagmography by calculating the percent of change in pupillary diameter in unit time during fixation to an accommodative target, light reaction, convergence, and divergence., Results: There were significant differences between groups in the reaction during fixation (p: 0.01), in light reaction (p: 0.014), and in divergence-induced mydriasis (p: 0.003). In all of these, the difference between control eyes and pseudoexfoliative eyes of patients with PXS was significant., Conclusions: Pupillometry seems to be a promising noninvasive method to detect the clinical signs of PXS and may be useful for an accurate diagnosis.

Objective: To determine the pathogenesis of the bullous keratopathy that is frequently observed in patients after argon laser iridotomy (ALI) by comparing the changes in aqueous flow after ALI with those that follow peripheral iridectomy in rabbit eyes., Methods: Silicone particles were injected into the anterior chamber of rabbit eyes as tracers to monitor aqueous flow. Particle tracking velocimetry with image analysis was used to determine the direction and speed of aqueous flow in 5 pigmented rabbits that underwent ALI and 5 that underwent peripheral iridectomy., Results: In the ALI group, silicone particles were found to stream through the iridotomy window against the corneal endothelium immediately after the pupil was constricted by a light stimulus. The mean +/- SD speed of the particles was 2.97 +/- 1.51 mm/s. In contrast, the mean +/- SD flow rate through the iridectomy window in the peripheral iridectomy group was significantly slower at 0.36 +/- 0.30 mm/s (P = .01)., Conclusion: Constriction of the pupil elicited marked aqueous streaming through the ALI window against the corneal endothelium. Clinical Relevance The mechanical stress to the corneal endothelium by the abnormal aqueous stream may be partially responsible for the corneal decompensation that follows ALI.

Purpose: To evaluate the effectiveness of the pupil center as an anatomic landmark for excimer laser treatments., Setting: Sekal-Microchirurgia-Rovigo Centre, Rovigo, Italy., Methods: Pupillometry with the Costruzione Strumenti Oftalmici S.R.L. (CSO) pupil-measuring module (incorporated in Eye Top videokeratoscope) was performed in 52 patients with a diagnosis of myopia and in 25 patients with a diagnosis of hyperopia. Measurements both in mesopic and photopic conditions consisted of pupil diameters, spatial shift of the pupil center, and the distance between the pupil center and keratoscopic axis., Results: The mean pupil diameter in photopic conditions of illumination in myopic eyes was 3.52 mm +/- 0.56 (SD), while in mesopic conditions it was 5.37 +/- 0.78 mm; in hyperopic eyes the mean photopic pupil diameter was 3.01 +/- 0.46 mm, while the mean mesopic diameter was 5.12 +/- 0.48 mm. The mean spatial shift of the pupil center in myopic eyes was 0.086 mm (maximum 0.269 mm), while in the hyperopic eyes it was 0.095 mm (maximum 0.283 mm). The mean distance between the pupil center and keratoscopic axis in myopic eyes was 0.226 +/- 0.13 mm (maximum 0.75 mm), while in hyperopic eyes it was 0.45 +/- 0.19 mm (maximum 0.8 mm)., Conclusions: The mean of the measured pupil sizes was greater in myopic eyes than in hyperopic eyes. The spatial shift of the pupil center, as the pupil dilates, was relatively small in all groups; therefore, the pupil center is a good anatomic landmark for both traditional refractive surgery and wavefront-guided treatments. The mean distance between the keratoscopic axis and pupil center was greater in the hyperopic group than in the myopic group. Therefore, centration of any laser treatment on the basis of the keratoscopic analysis should be done carefully, especially in hyperopic eyes and in cases in which the pupil center is meaningfully shifted from keratoscopic axis, even in photopic conditions of illumination.

The irises of both Lophius piscatorius (goosefish) and Opsanus tau (toadfish), like those of many other vertebrates, have a photosensitive sphincter pupillae that responds autonomously to light. The iris also constricts when exposed to either cholinergic or adrenergic agonists. Our data suggest that the adrenergic response is nonspecific and that the irises of both species receive primarily cholinergic innervation. However, both cholinergic and adrenergic agonists are capable of modifying the autonomous response of the iris to light.