Association between Iris Biological Features and Corneal Biomechanics in Myopic Eyes.

PURPOSE: Iris biological features such as surface features and profile characteristics reflected the development of iris stroma and microvessels. Iris vessels and microcirculation are still lack of effective detection methods, and we can directly observe only the iris surface biological characteristics. This cross-sectional study evaluated the association between iris surface biological features and corneal biomechanics in young adults with myopia. METHODS: We recruited 152 patients with myopia aged ≥18 years, from the Eye Hospital of Wenzhou Medical University, who had complete Corneal Visualization Scheimpflug Technology (Corvis ST) data and graded iris surface features. Iris surface features included crypts, furrows, and color measured from digital slit lamp images. The biomechanical properties of the cornea were assessed using Corvis ST. Only 1 eye of each participant was randomly selected for analysis. Associations between the iris surface features and corneal biomechanics were analyzed using linear regression models. The grade of iris crypts, furrows, and color and corneal biomechanical parameters measured with Corvis ST was the main outcome measures. RESULTS: The iris crypts were significantly associated with deflection amplitude at the first applanation (A1 DLA, ß = 0.001, P = 0.013), A1 delta arc length (A1 dArcL) (ß = -0.001, P = 0.01), maximum delta arc length (dArcLM) (ß = -0.004, P = 0.03), and stiffness at the first applanation (SP-A1) (ß = -2.092, P = 0.016). The iris furrows were only associated with integrated radius (ß = -0.212, P = 0.025). Iris color was found not related with corneal biomechanical parameters measured via Corvis ST. CONCLUSIONS: Iris surface features were associated with corneal biomechanical properties in myopic eyes; more iris crypts were associated with lower corneal stiffness while more extensive furrows were related with higher corneal stiffness. Iris crypts and furrows may provide useful information on corneal biomechanical properties in myopic eyes.

Changes in Iris Stiffness and Permeability in Primary Angle Closure Glaucoma.

Purpose: To evaluate the biomechanical properties of the iris by evaluating iris movement during pupil constriction and to compare such properties between healthy and primary angle-closure glaucoma (PACG) subjects. Methods: A total of 140 subjects were recruited for this study. In a dark room, the anterior segments of one eye per subject were scanned using anterior segment optical coherence tomography imaging during induced pupil constriction with an external white light source of 1700 lux. Using a custom segmentation code, we automatically isolated the iris segments from the AS-OCT images, which were then discretized and transformed into a three-dimensional point cloud. For each iris, a finite element (FE) mesh was constructed from the point cloud, and an inverse FE simulation was performed to match the clinically observed iris constriction in the AS-OCT images. Through this optimization process, we were able to identify the elastic modulus and permeability of each iris. Results: For all 140 subjects (95 healthy and 45 PACG of Indian/Chinese ethnicity; age 60.2 ± 8.7 for PACG subjects and 57.7 ± 10.1 for healthy subjects), the simulated deformation pattern of the iris during pupil constriction matched well with OCT images. We found that the iris stiffness was higher in PACG than in healthy controls (24.5 ± 8.4 kPa vs. 17.1 ± 6.6 kPa with 40 kPa of active stress specified in the sphincter region; P < 0.001), whereas iris permeability was lower (0.41 ± 0.2 mm2/kPa s vs. 0.55 ± 0.2 mm2/kPa s; p = 0.142). Conclusions: This study suggests that the biomechanical properties of the iris in PACG are different from those in healthy controls. An improved understanding of the biomechanical behavior of the iris may have implications for the understanding and management of angle-closure glaucoma.

Expanding the clinical spectrum and management of Traboulsi syndrome: report on two siblings homozygous for a novel pathogenic variant in ASPH.

BACKGROUND: Traboulsi syndrome is a very rare, syndromic form of ectopia lentis that is potentially sight-threatening at a young age. It is characterized by typical facial, skeletal and ocular signs. MATERIALS AND METHODS: Two siblings, born to consanguineous parents, with a clinical phenotype consistent with Traboulsi syndrome, underwent extensive ophthalmic imaging and exome-based genetic testing. Both were treated with unilateral clear lens extraction via a limbal approach. RESULTS: Two siblings, one male and one female, presented with systemic and ocular features consistent with Traboulsi syndrome. Lens subluxation was present in all 4fouraffected eyes, and spontaneous subconjunctival bleb formation was detected in one eye. This eye also showed evidence of keratoconus-related corneal thinning. The clinical diagnosis of Traboulsi syndrome was confirmed molecularly. A homozygous, novel, pathogenic nonsense variant was identified in exon 25 of the ASPH gene: c.2181_2183dup, p.(Val727_Trp728insTer). Excellent visual outcomes following clear lens extraction and postoperative rigid gas-permeable contact lens fitting were obtained. CONCLUSIONS: We expanded the genetic spectrum of Traboulsi syndrome with a novel frameshift variant in the ASPH gene. We showed that lensectomy followed by gas-permeable contact lenses is an efficient therapeutic approach to treat lens subluxation in Traboulsi syndrome. However, lifelong follow-up is crucial to avoid (late) postoperative complications.

A Digital Microscreen for the Enhanced Appearance of Ocular Prosthetic Motility (an American Ophthalmological Society Thesis).

PURPOSE: This study aims to improve the apparent motility of ocular prosthetic devices using technology. Prevailing ocular prostheses are acrylic shells with a static eye image rendered on the convex surface. A limited range of ocular prosthetic movement and lack of natural saccadic movements commonly causes the appearance of eye misalignment that may be disfiguring. Digital screens and computational systems may obviate current limitations in eye prosthetic motility and help prosthetic wearers feel less self-conscious about their appearance. METHODS: We applied convoluted neural networks (CNNs) to track pupil location in various conditions. These algorithms were coupled to a microscreen digital prosthetic eye (DPE) prototype to assess the ability of the system to capture full ocular ductions and saccadic movements in a miniaturized, portable, and wearable system. RESULTS: The CNNs captured pupil location with high accuracy. Pupil location data were transmitted to a miniature screen ocular prosthetic prototype that displayed a dynamic contralateral eye image. The transmission achieved a full range of ocular ductions and with grossly undetectable latency. Lack of iris and sclera color and detail, as well as constraints in luminosity, dimensionality and image stability limited the real eye appearance. Yet, the digitally rendered eye moved in the same amplitude and velocity as the native, tracked eye. CONCLUSIONS: Real-time image processing using CNNs coupled to microcameras and a miniscreen DPE may offer improvements in amplitude and velocity of apparent prosthetic eye movement. These developments, along with ocular image precision, may offer a next-generation eye prosthesis. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Iris and its relevance to angle closure disease: a review.

Glaucoma is a leading cause of irreversible visual impairment, and primary angle closure glaucoma (PACG) affects Asians disproportionately. Whereas advances in ocular imaging have identified several anatomical risk factors, our ability to predict PACG still requires considerable improvement. The iris plays a crucial role in the pathophysiology of angle closure disease, either through a mechanical or vascular mechanism. Irises of closed-angle eyes inhibit vastly different structural constituents as compared with those of open-angle eyes, thereby effecting variations in biomechanical properties and iris fluid conductivity. The clinical consequences include a smaller change in iris volume on pupil dilation in closed-angle eyes, thereby bringing the iris and trabecular meshwork closer in apposition. In this review, we summarise the potential role of the iris in the pathogenesis of angle closure disease.

In vivo estimation of murine iris stiffness using finite element modeling.

The iris plays an important role in certain types of glaucoma, including primary angle-closure glaucoma and pigmentary glaucoma. Iris mechanics are also important in influencing trabecular meshwork deformation in response to intraocular pressure changes in some animal species. Although mice are widely used to study ocular disease, including glaucoma, the in vivo biomechanical properties of the murine iris are unknown. Thus, the primary objective of this study was to estimate murine iris biomechanical stiffness. We used optical coherence tomography (OCT) images of the anterior segment of living mice (n = 13, age = 7.3 ± 3.2 [mean ± SD] months) at sequentially increasing IOP levels, observing IOP-dependent iris deformations. We then used an inverse finite element model to predict iris deformations under the same conditions, estimating iris stiffness by maximizing agreement between OCT data and numerical simulations. Our results show an in vivo murine iris stiffness of 96.1 ± 54.7 kPa (mean ± SD), which did not correlate with age but was dependent on gender. Our results further showed strong evidence of reverse pupillary block, with mean posterior chamber pressure remaining at approximately 12 mmHg even as anterior chamber pressure was set to much higher levels. Our approach to monitoring iris stiffness in vivo is applicable to study potential changes of iris stiffness in various pathophysiological conditions and thus has significant potential for clinical care of ocular disease involving iris biomechanics.

Anatomical Changes in the Anterior Chamber Volume After Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To evaluate changes in the anterior chamber of eyes that have undergone Descemet membrane endothelial keratoplasty (DMEK) and to identify factors that affect these changes. METHODS: This retrospective study included 25 pseudophakic eyes of 25 patients who underwent DMEK. We determined the preoperative and postoperative values of the best spectacle-corrected visual acuity, spherical equivalent (SE), anterior chamber volume (ACV), anterior chamber depth (ACD), central corneal thickness (CCT), and scleral spur angle (SSA) evaluated using anterior segment optical coherence tomography and iris damage score and iris posterior synechiae score. We defined ∆ as the average change rate from the preoperative to postoperative value for each factor at 1 month (SE at 6-12 months) postoperatively. We also analyzed correlations between ∆ACV, ∆SE, and other preexisting factors. RESULTS: Compared with the preoperative ACV value (128 ± 28 mm3), the postoperative value significantly increased to 155 ± 21 mm3 (P < 0.001); ∆SE was +1.01 ± 1.09 diopters. ∆ACV was negatively correlated with preoperative ACD (R = 0.643, P < 0.001) and SSA (R = 0.555, P = 0.001) and positively correlated with ∆ACD (R = 0.799, P < 0.001) and ∆SSA (R = 0.608, P < 0.001). ∆CCT, iris damage score, and iris posterior synechiae score were not significantly correlated with ∆ACV. ∆SE was positively correlated with ∆ACV, ∆ACD, and ∆SSA (R = 0.680, 0.455, and 0.478; P < 0.001, <0.05, and <0.05, respectively). CONCLUSIONS: An increase in the ACV and hyperopic change was noted after successful DMEK, especially in eyes with narrow-angled shallow anterior chambers.

Cloudy complication: management of an opacified intraocular lens and diffuse iris transillumination defects: August consultation #1.

A 76-year-old man with a medical history of type 2 diabetes, hypercholesterolemia, and coronary artery disease presented with blurred vision in the right eye. His ocular history was significant for cataract surgery with posterior chamber intraocular lens (PC IOL) implantation in both eyes 3 years prior to presentation. His specific ocular complaints included blurred vision, whiteout visual episodes lasting 20 minutes, and intractable glare in the right eye. Of note, the patient was on anticoagulation therapy due to a history of stroke.On examination, the corrected distance visual acuity (CDVA) was 20/50 in the right eye and 20/25 in the left eye with a manifest refraction of plano -0.50 × 70 degrees in the right eye and plano -050 × 170 degrees in the left eye. Pupils were round and reactive in both eyes. However, there was a 3+ relative afferent pupillary defect with a corresponding constricted confrontational visual field test in the right eye. The left eye was unremarkable. Intraocular pressure (IOP) measured 14 mm Hg in the right eye and 12 mm Hg in the left eye by applanation tonometry, and the IOP was under excellent control on Timolol 0.5% 1 eyedrop twice a day and latanoprost every night at bedtime in the right eye.Pertinent findings on slitlamp examination of the right eye included a mild protective ptosis of the right upper eyelid, diffuse iris transillumination defects resembling the outline of the PC IOL (), and 2+ pigmented cell in the anterior chamber in the right eye. Gonioscopy revealed 3+ pigmented cell for 360 degrees without peripheral anterior synechiae in the right eye. A 1-piece acrylic toric PC IOL (SN6ATX, Alcon Laboratories, Inc.) was present in the ciliary sulcus with mild pseudophacodonesis and an open posterior capsule. In addition, there was a large discontinuous anterior capsule opening. Optic nerve examination revealed 0.9 cup-to-disc ratio (CDR) with diffuse 2+ pallor in the right eye and 0.4 CDR and a healthy neuroretinal rim in the left eye. The remainder of the dilated fundus examination was unremarkable without diabetic retinopathy or macular edema in either eye.(Figure is included in full-text article.)An opaque contact lens trial was performed for the right eye and the patient noted significant improvement in glare symptoms. Therefore, the surgical plan was to perform IOL exchange with a secondary IOL placement and artificial iris (HumanOptics AG) (AI) implantation using scleral fixation. However, the AI was cost-prohibitive at the time, and the patient decided to proceed with the IOL exchange alone.The patient had uneventful IOL exchange of the malpositioned PC IOL in the sulcus for an AO60 IOL (Bausch & Lomb, Inc.) with a pars plana-assisted anterior vitrectomy. Two months postoperatively, CDVA was 20/30 + 2 in the right eye with a manifest refraction of -0.50-2.00 × 30.At the 2-month postoperative visit, the patient reported increased flashes and cobweb-type floaters. He was diagnosed with a superior retinal horseshoe tear and an early macula-on retinal detachment. He underwent an uneventful pars plana vitrectomy (PPV), endolaser, and SF6 gas. Unfortunately, the patient experienced redetachment 2 weeks later requiring C3F8 gas. At the 6-week IOP check, the patient was noted to have early central opacification of the IOL (). IOL opacification continued to progress and the vision declined to CDVA of 20/200 by 3 months postoperatively ().(Figure is included in full-text article.)(Figure is included in full-text article.)What is the next step in management for this patient given the comorbidities of an opacified IOL, advanced glaucoma, anticoagulation status, and diffuse 360 degrees transillumination iris defects?

Exploring the Occurrence Mechanisms of Acute Primary Angle Closure by Comparative Analysis of Ultrasound Biomicroscopic Data of the Attack and Fellow Eyes.

PURPOSE: To explore the anatomical characteristics and occurrence mechanisms of acute primary angle closure (APAC) by comparing the quantitative data of UBM images of the APAC and fellow eyes. METHODS: 131 patients (262 eyes) were studied over five years by retrospective analysis. The quantitative data from UBM images including angle opening distance at 500 µm (AOD500), trabecular-iris angle (TIA), iris convexity (IC), iris span (IS), iris-lens angle (ILA), iris-lens contact distance (ILCD), iris-ciliary process angle (ICPA), and limbus-ciliary body angle (LCBA) were retrospectively recorded; comparative analysis of the APAC and fellow eyes was performed. RESULTS: The superior, inferior, nasal, temporal, and mean AOD500, TIA, IC, and LCBA (P < 0.001) were significantly smaller in APAC than in fellow eyes. Values of the lens thickness (LT), lens/axial length factor (LAF), lens position (LP), and relative lens position (RLP) were lower in APAC than in fellow eyes (P = 0.021; P = 0.025; P < 0.001; and P < 0.001). In APAC eyes, AOD500 was significantly positively correlated with IC, ILCD, and LCBA; TIA was significantly positively significantly correlated with IC, ILCD, and LCBA. In fellow eyes, AOD500 was significantly negatively correlated with ILA and significantly positively correlated with ILCD, ICPA, LCBA, axial length (AL), central anterior chamber depth (CACD), and LP; TIA was significantly negatively correlated with ILA and significantly positively correlated with IS, ILCD, ICPA, LCBA, AL, CACD, LP, and RLP. CONCLUSIONS: Multiple nonpupillary block factors (plateau iris, anterior attachment and insertion of the iris root, anterior shift of the lens, and anterior rotation of the ciliary body) promote the occurrence of APAC, and abnormal positional relationships of the iris, ciliary body, and lens may contribute to APAC.

Genetic mapping of autosomal recessive microspherophakia to chromosome 14q24.3 in a consanguineous Pakistani family and screening of exon 36 of LTBP2 gene.

Latent transforming growth factor beta binding protein 2 (LTBP2) plays a critical role in the development of connective tissue structure and function. Mutations in gene encoding LTBP2 are known to cause syndromic and a non-syndromic microspherophakia. Here, we present a 'first' report of genetic linkage of microspherophakia (MSP) to LTBP2 locus in a large consanguineous Pakistani family with four affected individuals in three loops. Using polymorphic microsatellite markers, haplotypes and linkage analysis, the diseased phenotype in MSP001 family was mapped to the LTBP2 gene. A maximum two point Logarithm of the odds (LOD) score of 4.16 was obtained with marker D14S284 at θ =0. Mutational analysis of exon 36 of LTBP2 using Sanger's sequencing did not reveal any previously reported mutations. Further analysis of the remaining exons are required to identify the causative variant.

Lower- and higher-order aberrations after photorefractive keratectomy with and without compensation of pupil centroid shift: fellow eye comparison.

PURPOSE: To study the effect of pupil centroid shift (PCS) compensation on lower- and higher-order aberrations (HOAs) after photorefractive keratectomy (PRK). SETTING: Labbafinejad Medical Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran. DESIGN: Prospective intrasubject fellow eye study. METHODS: One hundred twelve eyes of 56 patients with simple myopia or myopic astigmatism scheduled for PRK were enrolled. Preoperatively, the amount of PCS was measured in the horizontal and vertical directions. All eyes received wavefront-optimized treatment with static cyclotorsion compensation. PCS compensation was turned on for the right eye of each subject (PCS-on group), and turned off for the left eye (PCS-off group). Postoperatively, refraction and corneal HOAs were compared between the study groups at 6 months. RESULTS: Mean preoperative myopia was -3.84 diopters (D) ± 2.41 (SD) vs -3.75 ± 2.27 D (P = .408), whereas mean preoperative cylinder was -1.18 D ± 1.15 (SD) vs -1.14 ± 1.16 D (P = .769) in the PCS-on and PCS-off groups, respectively. Mean absolute PCS values were 62.25 µm ± 41.82 (SD) vs 55.92 ± 37.47 µm (P = .45) in the horizontal direction and 65.04 ± 47.16 µm vs 58.40 ± 45.44 µm in the vertical direction (P = .29) in the PCS-on and PCS-off groups, respectively. The study groups were comparable in terms of postoperative refraction and root mean square of total corneal HOAs. CONCLUSIONS: Compensation of PCS did not affect lower- and higher-order aberrations after wavefront-optimized PRK with static cyclotorsion compensation in myopic or myopic astigmatic eyes.

Genetic Heritability of Pigmentary Glaucoma and Associations With Other Eye Phenotypes.

Importance: Mechanisms behind pigmentary glaucoma, a form of early-onset glaucoma that may potentially lead to severe visual impairment or blindness, are poorly understood. Objective: To calculate the single-nucleotide polymorphism (SNP) heritability of pigmentary glaucoma and identify genetic associations with the disease. Design, Setting and Participants: This genome-wide association study included affected individuals from Germany and control participants from the United Kingdom. Genome-wide information was obtained for patients with pigmentary glaucoma and control participants free of glaucoma by using the Illumina Human Omni Express Exome 8v1-2 chip and genomic imputation. The SNP heritability of pigmentary glaucoma was estimated through a restricted maximum likelihood analysis. Associations between the genetic variants and pigmentary glaucoma obtained from age, sex, and principal component-adjusted logistic regression models were compared with those of SNPs previously associated with other eye phenotypes using Pearson product-moment correlations. Data were collected from November 2008 to January 2018, and analysis was completed between April 2018 and August 2019. Main Outcomes and Measures: An estimate of SNP-explained heritability for pigmentary glaucoma; correlations of effect sizes between pigmentary glaucoma and iris pigmentation and myopia; and correlations of effect sizes between pigmentary glaucoma and other eye phenotypes. Results: A total of 227 affected individuals (mean [SD] age, 58.7 [13.3] years) and 291 control participants (mean [SD] age, 80.2 [4.9] years) were included; all were of European ancestry. The SNP heritability of pigmentary glaucoma was 0.45 (SE, 0.22; P = 6.15 × 10-10). Twelve SNPs previously reported with genome-wide significant associations with eye pigmentation were associated with pigmentary glaucoma's SNP heritability (4.9% SNP heritability; 0.022; P = 6.0 × 10-4). Pigmentary glaucoma SNP effect sizes were correlated moderately for myopia (r, 0.42 [95% CI, 0.14-0.63]; P = 4.3 × 10-3) and more strongly with those for iris pigmentation (r = -0.69 [95% CI, -0.91 to -0.20]; P = .01), although this was nonsignificant per a strict adjusted significance threshold (P < .01). Conclusions and Relevance: These findings support the conclusion that pigmentary glaucoma may have a genetic basis and be highly heritable. Variants associated with lighter eye color and myopia appear to be associated with increased risk of pigmentary glaucoma, but no shared genetic basis with primary open-angle glaucoma (or its quantitative endophenotype of cup-disc ratio) was observed.

A C1976Y missense mutation in the mouse Ip3r1 gene leads to short-term mydriasis and unfolded protein response in the iris constrictor muscles.

Ip3r1 encodes an inositol 1,4,5-trisphosphate-responsive calcium channel. Mutations in the IP3R1 gene in humans may cause Gillespie syndrome (GS) typically presents as fixed dilated pupils in affected infants, which was referred to as iris hypoplasia. However, there is no report of mice with Ip3r1 heterozygous mutations showing dilated pupils. Here, we report a new Ip3r1 allele with short-term dilated pupil phenotype derived from an N-ethyl-N-nitrosourea (ENU) mutagenesis screen. This allele carries a G5927A transition mutation in Ip3r1 gene (NM_010585), which is predicted to result in a C1976Y amino acid change in the open reading frame of IP3R1 (NP_034715). We named this novel Ip3r1 allele Ip3r1C1976Y. Histology and pharmacological tests show that the dilated pupil phenotype is a mydriasis caused by the functional defect in the iris constrictor muscles in Ip3r1C1976Y. The dilated pupil phenotype in Ip3r1C1976Y was referred to as mydriasis and excluding iris hypoplasia. IHC analysis revealed increased expression of BIP protein, the master regulator of unfolded protein response (UPR) signaling, in Ip3r1C1976Y mice that did not recover. This study is the first report of an Ip3r1 mutation being associated with the mydriasis phenotype. Ip3r1C1976Y mice represent a self-healing model that may be used to study the therapeutic approach for Ip3r1-related diseases.

Computational Study on the Biomechanics of Pupil Block Phenomenon.

Pupil blocking force (PBF) can indicate the potential risk of pupil block (PB), which is considered as a main pathogenic factor of primary angle-closure glaucoma (PACG). However, the effect of PB on the PBF under different pupil diameters and iris-lens channel (ILC) distance was unknown. Besides, a simple and practical method to assess PBF has not been reported yet. In this study, 21 finite element models of eyes with various pupil diameters (2.4 mm-2.6 mm) and ILC (2 µm-20 µm) were constructed and were conducted to simulate aqueous humor flow by fluid-solid coupling numerical simulation. PBF in each model was calculated based on the numerical simulation results and was fitted using response surface methodology. The results demonstrated that ILC distance had a more significant effect than pupil diameter on PBF. With the decrease of ILC distance, the PBF increased exponentially. When the reduced distance was lower than 5 µm, the PBF exploded quickly, resulting in a high risk of iris bomb. The PBF also varied with pupil diameter, especially under the condition of narrow ILC. Both ILC distance and pupil diameter could explain more than 97% variation in PBF, and a second-order empirical model has been developed to be a good predictor of PBF. Based on the linear relationship between anterior chamber deformation and PBF, a threshold value of PBF was given to guide clinical decisions. This study could be used to investigate PACG pathological correlation and its pathogenesis, so as to provide a reference value for clinical diagnosis of PACG.

The Pupil.

PURPOSE OF REVIEW: The goal of this article is to review the anatomy and physiology of pupillary function and then employ that information to develop a comprehensive framework for understanding and diagnosing pupillary disorders. RECENT FINDINGS: The contribution of rods and cones to the pupillary light reflex has long been known. A third photosensitive cell type, the intrinsically photosensitive retinal ganglion cell, has recently been discovered. This cell type employs melanopsin to mediate a portion of the pupillary light reflex independent of rods and cones (the postillumination pupillary response) and photic regulation of circadian rhythm. SUMMARY: The autonomic nervous system regulates pupil size in response to stimuli. The parasympathetic nervous system causes miosis in response to light and near visual stimuli. These stimuli activate supranuclear pathways that project to the Edinger-Westphal nuclei. The sympathetic nervous system causes mydriasis in response to a variety of arousing factors, both physiologic (wakefulness) and pathologic (pain). Abnormalities of physiologic function cause disturbances of pupil size, shape, and response to stimuli. The clinical approach to pupillary abnormalities should focus on the clinical and pharmacologic assessment of the pupil's expected response to diverse stimuli.

Phacoemulsification Cataract Surgery Affects the Discriminative Capacity of Iris Pattern Recognition.

Cataract is a common ophthalmic disorder and the leading cause of blindness worldwide. While cataract is cured via surgical procedures, its impact on iris based biometric recognition has not been effectively studied. The key objective of this research is to assess the effect of cataract surgery on the iris texture pattern as a means of personal authentication. We prepare and release the IIITD Cataract Surgery Database (CaSD) captured from 132 cataract patients using three commercial iris sensors. A non-comparative non-randomized cohort study is performed on the iris texture patterns in CaSD and authentication performance is studied using three biometric recognition systems. Performance is lower when matching pre-operative images to post-operative images (74.69 ± 9.77%) as compared to matching pre-operative images to pre-operative images (93.42 ± 1.76%). 100% recognition performance is observed on a control-group of healthy irises from 68 subjects. Authentication performance improves if cataract affected subjects are re-enrolled in the system, though re-enrollment does not ensure performance at par with pre-operative scenarios (86.67 ± 5.64%). The results indicate that cataract surgery affects the discriminative nature of the iris texture pattern. This finding raises concerns about the reliability of iris-based biometric recognition systems in the context of subjects undergoing cataract surgery.

Iris recognition under the influence of diabetes.

In this study, iris recognition under the influence of diabetes was investigated. A new database containing 1318 pictures from 343 irides - 546 images from 162 healthy irides (62% female users, 38% male users, 21% <20 years old, 61% (20) < 40 years old, 12% (40) <60 years old and 6% more than 60 years old) and 772 iris images from 181 diabetic eyes but with a clearly visible iris pattern (80% female users, 20% male users, 1% <20 years old, 17.5% (20) <40 years old, 46.5% (40) <60 years old and 35% more than 60 years old) - were collected. All of the diabetes-affected eyes had clearly visible iris patterns without any visible impairments and only type II diabetic patients with at least 2 years of being diabetic were considered for the investigation. Three different open source iris recognition codes and one commercial software development kit were used for achieving the iris recognition system's performance evaluation results under the influence of diabetes. For statistical analysis, the t-test and the Kolmogorov-Simonov test were used.

Static and dynamic pupillary characteristics in high myopic eyes with two implantable collamer lenses.

PURPOSE: To determine static and dynamic pupillometry characteristics before and after implantable collamer lens (ICL) (V4 and V4c) implantation. SETTING: Shanghai, China. DESIGN: Prospective consecutive observational case series. METHODS: Patients who had either V4 or V4c ICL implantation were included in this observational study. An automatic quantitative pupillometry system (MonCv3) was used for pupillometry preoperatively and 1 week, 1 month, and 3 months after surgery. Static pupillometry measurements (pupil diameters [PDs] at 4 standardized illumination levels) and dynamic parameters (including initial PD, amplitude of contraction, latency of contraction, duration of contraction, velocity of contraction, latency of dilation, duration of dilation, and velocity of dilation) were measured. RESULTS: The study comprised 98 eyes (50 patients). Mesopic and low photopic PDs declined by 0.32 mm and 0.27 mm, respectively, at 3 months after ICL implantation; scotopic PD declined at 1 week and recovered to preoperative levels at 3 months; and high photopic PD remained unchanged. Regarding the pupil light reflex, contraction amplitude and velocity declined after surgery, whereas other dynamic parameters remained unchanged. The static and dynamic pupillary characteristics were similar between the V4 and V4c ICL groups. CONCLUSIONS: The V4 and V4c ICLs had similar influences on iris motility. ICL implantation had a miotic effect under mesopic and low photopic illumination conditions, resulting in decreases in pupil contraction amplitude and velocity in light reflexes.

Determination of iris thickness development in children using swept-source anterior-segment optical coherence tomography.

PURPOSE: The uvea comprises the iris, ciliary body, and choroid. However, the development of the anterior part (iris and ciliary body) in children is not yet fully elucidated. We investigated the iris thickness (IT) in children using swept-source anterior-segment optical coherence tomography (ASOCT). METHODS: In this retrospective, clinic-based study, we enrolled 41 children (mean ± standard deviation: 6.8 ± 3.3 years; range: 3-16; 17 males) with normal or mild refractive error. Horizontal scanning images of swept-source ASOCT were analyzed in temporal and nasal angle areas. The ITs at 1 and 2 mm from the pupil edge were measured using swept-source ASOCT. The association between IT and age, sex, and ocular morphological parameters (i.e., axial length, average corneal curvature, central corneal thickness, inter-scleral spur distance, and anterior chamber depth) was assessed using Pearson's correlation coefficient (r) and linear regression analysis. RESULTS: The average IT (temporal and nasal) at 1 and 2 mm were 0.432 ± 0.060 (0.302-0.569 mm) and 0.337 ± 0.045 (0.229-0.414 mm), respectively. There was a significant correlation between age and average IT (r = 0.45, P = 0.002 at 1 mm and r = 0.31, P = 0.042 at 2 mm). Multiple linear regression analysis revealed that age (coefficient: 0.01), axial length (-0.02), average corneal curvature (0.01), and anterior chamber depth (0.01) at 1 mm as well as age (0.00), average corneal curvature (0.09), anterior chamber depth (0.06), and male (-0.02) at 2 mm were identified as predictors of IT. CONCLUSIONS: IT in children increases with age. Additionally, IT was thinner with longer axial length and in males, thicker in eyes with deeper anterior chamber and flatter corneal curvature. Our study may partly explain the development of eyeball structures in children.