Evaluating Chatbot responses to patient questions in the field of glaucoma.

Objective: The aim of this study was to evaluate the accuracy, comprehensiveness, and safety of a publicly available large language model (LLM)-ChatGPT in the sub-domain of glaucoma. Design: Evaluation of diagnostic test or technology. Subjects participants and/or controls: We seek to evaluate the responses of an artificial intelligence chatbot ChatGPT (version GPT-3.5, OpenAI). Methods intervention or testing: We curated 24 clinically relevant questions in the domain of glaucoma. The questions spanned four categories: pertaining to diagnosis, treatment, surgeries, and ocular emergencies. Each question was posed to the LLM and the responses obtained were graded by an expert grader panel of three glaucoma specialists with combined experience of more than 30 years in the field. For responses which performed poorly, the LLM was further prompted to self-correct. The subsequent responses were then re-evaluated by the expert panel. Main outcome measures: Accuracy, comprehensiveness, and safety of the responses of a public domain LLM. Results: There were a total of 24 questions and three expert graders with a total number of responses of n = 72. The scores were ranked from 1 to 4, where 4 represents the best score with a complete and accurate response. The mean score of the expert panel was 3.29 with a standard deviation of 0.484. Out of the 24 question-response pairs, seven (29.2%) of them had a mean inter-grader score of 3 or less. The mean score of the original seven question-response pairs was 2.96 which rose to 3.58 after an opportunity to self-correct (z-score - 3.27, p = 0.001, Mann-Whitney U). The seven out of 24 question-response pairs which performed poorly were given a chance to self-correct. After self-correction, the proportion of responses obtaining a full score increased from 22/72 (30.6%) to 12/21 (57.1%), (p = 0.026, χ2 test). Conclusion: LLMs show great promise in the realm of glaucoma with additional capabilities of self-correction. The application of LLMs in glaucoma is still in its infancy, and still requires further research and validation.

Three-Year Outcomes of the Paul Glaucoma Implant for Treatment of Glaucoma.

PRCIS: In our case series, the 3-year failure for Paul Glaucoma Implant (PGI) implantation was 14.6%. At 3 years postoperatively, there was a significant reduction in mean intraocular pressure (IOP) and the number of glaucoma medications used. OBJECTIVE: To determine the 3-year efficacy and safety of the PGI, a novel glaucoma tube shunt in patients with glaucoma. METHODS: Retrospective review of all patients who had undergone PGI implantation in a single tertiary institution in Singapore between May 1, 2017 and January 1, 2022. Data were extracted from electronic health records (Computerized Patient Support System 2 and Epic). The primary outcome measure was failure, defined as IOP >18 mm Hg or <6 mm Hg on 2 consecutive visits after 3 months, reoperation for IOP-related indication, explantation of implant, or loss of light perception vision. Complete success was defined as the absence of failure without medications at 36 months, and qualified success similarly, but with medications. Postoperative mean IOP, mean number of IOP-lowering medications used, and visual acuity were also assessed. RESULTS: Forty-eight eyes in 48 patients were identified. Thirty-one patients (64.6%) had primary open angle and angle closure glaucoma, and 18 (37.5%) had previous existing tube implants or trabeculectomy. At 3 years postoperatively, 7 cases (14.6%) fulfilled the criteria for failure and 36 (75%) met the criteria for complete success. The mean IOP at 36 months was 14.9 ± 4.11 mm Hg, from the mean preoperative IOP of 20.6 ± 6.13 mm Hg ( P < 0.001). The mean number of IOP-lowering medications used was reduced from 3.13 ± 0.959 preoperatively to 0.167 ± 0.476 at 36 months ( P < 0.001). The most common postoperative complication was hypotony (n = 17, 35.4%), of which the majority were self-limiting, followed by hyphema (n = 5, 10.4%) and tube exposure (n = 4, 8.3%). CONCLUSION: The PGI demonstrated sustained IOP reduction and a reduction of medication burden at 3 years postoperatively.

Two-Year Outcomes of the Paul Glaucoma Implant for Treatment of Glaucoma.

PURPOSE: To determine 2-year efficacy of the PAUL Glaucoma Implant (PGI), a novel glaucoma tube shunt in patients with advanced glaucoma. PARTICIPANTS: Patients with glaucoma refractory to maximum medical therapy or previous failed glaucoma surgery. METHODS: Retrospective review of all patients who had underwent PGI implantation in a single tertiary institution between May 1, 2017 and March 30, 2021. MAIN OUTCOME MEASURES: Primary outcome measure was failure defined as intraocular pressure (IOP) >18 mm Hg or <6 mm Hg on 2 consecutive visits after 3 months, reoperation for IOP-related indication, explantation of implant or loss of light perception vision. Complete success was defined as unmedicated IOP ≤18 mm Hg or ≥6 mm Hg in the absence of failure. RESULTS: Forty-five eyes in 45 patients were identified, with mean follow-up duration of 24.9±2.0 months. Thirty patients (66.7%) had primary glaucoma and 11 (24.4%) with previous glaucoma surgery. At 2 years following surgery, 8 eyes (17.8%) fulfilled the failure criteria with 32 eyes (71.1%) achieving complete success. Compared with mean medicated preoperative IOP (19.8±6.3 mm Hg), postoperative IOP at 24 months was 13.9±3.7 (P<0.01). Mean number of medications decreased from 3.2±0.8 preoperatively to 0.29±0.65 at 24 months (P<0.01). Significant complications included self-limiting shallow anterior chamber (n=10; 22.2%), hypotony requiring intervention (n=4; 8.9%) and tube occlusion (n=4; 8.9%). CONCLUSIONS: The PGI was able to achieve sustained IOP reduction with reduction of medications at 2 years postsurgery in patients with advanced glaucoma.

Comparison of refractive outcomes after combined cataract and glaucoma surgery: trabeculectomy and glaucoma drainage device implantation.

PURPOSE: To investigate the refractive outcome of combined cataract surgery and glaucoma drainage device (GDD) implantation compared with trabeculectomy and cataract surgery. SETTING: Department of Ophthalmology, National University Health System, Singapore. DESIGN: Retrospective cohort study. METHODS: 206 eyes were enrolled for analysis: 50 had combined cataract surgery and trabeculectomy (trabeculectomy group), 50 had combined cataract surgery and GDD implantation (GDD group), and 106 had cataract surgery alone (control group). Refractive prediction error and absolute prediction error of each glaucoma surgery group were compared with the control group. Subgroup analysis was performed in the following axial length (AL) subgroups: short (<22.5 mm), medium (≥22.5 to <25.5 mm), and long (≥25.5 mm). RESULTS: In total, 206 eyes were examined. There was no statistically significant difference in the overall refractive prediction error between the GDD (0.00 ± 0.54 diopters [D]) and the control group (0.10 ± 0.53 D, P = .58). There was significant myopic refractive prediction error in the trabeculectomy group (-0.18 ± 0.88 D, P = .020). In eyes with short AL, a greater absolute prediction error was observed in the GDD group (-0.75 ± 0.43 D, P = .039). CONCLUSIONS: Apart from a significant deviation in short AL eyes, combined cataract surgery and GDD implantation demonstrated no significant postoperative refractive prediction error.

Efficacy and Safety of Repeated Micropulse Transscleral Diode Cyclophotocoagulation in Advanced Glaucoma.

PRECIS: Repeat micropulse transscleral cyclophotocoagulation (MPTCP) has some benefit in lowering intraocular pressure (IOP). There was a small risk of loss of vision, prolonged hypotony, and phthisis bulbi. AIM: This study aimed to determine the efficacy and safety of repeated MPTCP for an Asian population with refractory glaucoma. METHODS: This is a retrospective case series of 43 eyes (43 patients) with severe glaucoma which underwent repeated MPTCP. Baseline parameters were taken from the visit just before the second MPTCP session. Success was defined as IOP of 6 to 21 mm Hg or ≥20% reduction in IOP without an increase in glaucoma medication from baseline, without further glaucoma reoperation, and ≤3 total MPTCP episodes. The IOP, number of IOP-lowering medications, and best-corrected visual acuity were documented preoperatively and postoperatively. Postoperative complications were also analyzed. RESULTS: The mean age±SD was 57.4±18.2 years with a mean follow-up duration of 28.9±27.5 months. Neovascular glaucoma was the most common type of glaucoma [18 eyes (41.9%)]. The success rates at postoperative years 1, 2, and 3, and the latest follow-up were 36.4%, 42.9%, 32.0%, and 39.5%, respectively. The median survival time of repeat MPTCP was 4.6 months. Compared with the preoperative mean IOP (35.2±11.0 mm Hg), the mean IOP at postoperative years 1, 2, and 3, and latest follow-up, was 27.8±13.7 mm Hg (P=0.004), 27.4±12.4 (P=0.003), 31.8±13.2 (P=0.35), and 27.1±13.8 mm Hg (P=0.002), respectively. The mean number of IOP-lowering medications was reduced from 3.3±0.9 preoperatively to 2.8±1.3 at the final follow-up (P=0.007). Postoperative complications included prolonged hypotony [3 eyes (7.0%)] and phthisis bulbi [2 eyes (4.7%)]. CONCLUSION: Repeated MPTCP is at best moderately effective in lowering IOP for eyes with advanced glaucoma.

Clinical Efficacy and Safety Outcomes of Micropulse Transscleral Diode Cyclophotocoagulation in Patients With Advanced Glaucoma.

PRECIS: Micropulse transscleral cyclophotocoagulation (MPTCP) is only moderately effective in lowering intraocular pressure (IOP) and is useful as an adjunct procedure to other glaucoma surgeries. There was a small risk of loss of vision, prolonged hypotony, and phthisis bulbi. AIM: The aim of this study was to determine the efficacy and safety of a single MPTCP treatment for an Asian population with advanced glaucoma. METHODS: This is a retrospective single-center study of 207 eyes (207 patients) with advanced glaucoma which underwent first-time MPTCP between January 1, 2008, and March 31, 2018. Success was defined as IOP of 6 to 21 mm Hg or ≥20% reduction in IOP without an increase in glaucoma medication from baseline, and without glaucoma reoperation. The IOP, best-corrected visual acuity, and number of glaucoma medications were also analyzed. RESULTS: The mean (SD) age was 64.9±16.9 years. The mean follow-up duration was 18.7±16.2 months. The rate of success at postoperative years 1 and 2 follow-up was 44.1% and 32.6%, respectively. The median survival time of MPTCP was 9.0 months and 85 (40.9%) eyes received reoperation. The mean IOP decreased from 31.5±12.0 mm Hg preoperatively to 22.1±10.3 and 23.8±11.8 mm Hg at postoperative years 1 and 2, respectively (P<0.0001). The mean number of glaucoma medications was reduced from 3.3±1.0 preoperatively to 2.6±1.1 and 2.4±1.1 at postoperative years 1 and 2, respectively (P<0.0001). Significant complications included prolonged hypotony [1 eye (0.5%)], phthisis bulbi [7 eyes (3.4%)], and best-corrected visual acuity reduction [29 eyes (13.9%)]. CONCLUSION: Single first-time MPTCP for advanced glaucoma eyes was moderately effective in lowering IOP but >50% failed by 1 year.

Evolving Practice Patterns in Singapore's Public Sector Ophthalmology Centers During the COVID-19 Pandemic.

Coronavirus disease 19 (COVID-19) was first reported in Wuhan, China, in December 2019, and has since become a global pandemic. Singapore was one of the first countries outside of China to be affected and reported its first case in January 2020. Strategies that were deployed successfully during the 2003 outbreak of severe acute respiratory syndrome have had to evolve to contain this novel coronavirus. Like the rest of the health care services in Singapore, the practice of ophthalmology has also had to adapt to this rapidly changing crisis. This article discusses the measures put in place by the 3 largest ophthalmology centers in Singapore's public sector in response to COVID-19, and the challenges of providing eye care in the face of stringent infection control directives, staff redeployments and "social distancing." The recently imposed "circuit breaker," effectively a partial lockdown of the country, has further limited our work to only the most essential of services. Our staff are also increasingly part of frontline efforts in the screening and care of patients with COVID-19. However, this crisis has also been an opportunity to push ahead with innovative practices and given momentum to the use of teleophthalmology and other digital technologies. Amidst this uncertainty, our centers are already planning for how ophthalmology in Singapore will be practiced in this next stage of the COVID-19 pandemic, and beyond.

Reliability of Graders and Comparison with an Automated Algorithm for Vertical Cup-Disc Ratio Grading in Fundus Photographs.

INTRODUCTION: We aimed to investigate the intergrader and intragrader reliability of human graders and an automated algorithm for vertical cup-disc ratio (CDR) grading in colour fundus photographs. MATERIALS AND METHODS: Two-hundred fundus photographs were selected from a database of 3000 photographs of patients screened at a tertiary ophthalmology referral centre. The graders included glaucoma specialists (n = 3), general ophthalmologists (n = 2), optometrists (n = 2), family physicians (n = 2) and a novel automated algorithm (AA). In total, 2 rounds of CDR grading were held for each grader on 2 different dates, with the photographs presented in random order. The CDR values were graded as 0.1-1.0 or ungradable. The grading results of the 2 senior glaucoma specialists were used as the reference benchmarks for comparison. RESULTS: The intraclass correlation coefficient values ranged from 0.37-0.74 and 0.47-0.97 for intergrader and intragrader reliability, respectively. There was no significant correlation between the human graders' level of reliability and their years of experience in grading CDR (P = 0.91). The area under the curve (AUC) value of the AA was 0.847 (comparable to AUC value of 0.876 for the glaucoma specialist). Bland Altman plots demonstrated that the AA's performance was at least comparable to a glaucoma specialist. CONCLUSION: The results suggest that AA is comparable to and may have more consistent performance than human graders in CDR grading of fundus photographs. This may have potential application as a screening tool to help detect asymptomatic glaucoma-suspect patients in the community.

Outcomes and Complications of Scleral-Fixated Intraocular Lens Combined with Ahmed Tube Surgery.

BACKGROUND: To evaluate the outcome and complications of transscleral suture-fixated posterior chamber intraocular lens (PCIOL) implantation combined with Ahmed glaucoma valve (AGV) surgery in Asian eyes. DESIGN: This was a retrospective study that included 22 eyes from 22 participants. The surgeries were performed at Singapore's National University Hospital. Participants underwent an Ahmed tube surgery, together with transscleral suture-fixated posterior chamber intraocular lens. MAIN OUTCOME MEASURES: Complete success was defined as 6 ≤ intraocular pressure (IOP) ≤ 21 mmHg without medications at the last follow-up visit, with no reoperation required and no progression to no perception of light (NPL). RESULTS: At the last follow-up, there was a significant reduction in mean IOP (22.4 ± 6.5 mmHg versus 13.9 ± 3.9 mmHg; p < 0.001) and mean number of intraocular pressure-lowering medications (2.45 ± 1.30 versus 0.05 ± 0.21; p < 0.001). There was no significant change in visual acuity [1.43 ± 1.21 (LogMAR) versus 1.09 ± 1.31 (p = 0.204)]. Sixteen eyes (72.7%) achieved complete success. The 3 commonest complications were bullous keratopathy, choroidal detachment, and displacement of intraocular lens. CONCLUSION AND RELEVANCE: This technique showed good success for intraocular pressure control and vision preservation. Postoperative complications were relatively common although most were self-limiting. Patients at increased risk of trabeculectomy failure may be suitable for this procedure.

Cup-to-Disc Ratio From Heidelberg Retina Tomograph 3 and High-Definition Optical Coherence Tomography Agrees Poorly With Clinical Assessment.

PURPOSE: To investigate the agreement of vertical cup-to-disc ratio (VCDR) measured from Heidelberg Retina Tomograph 3 (HRT-3), high-definition optical coherence tomography (HD-OCT), and clinical grading. METHODS: A total of 933 consecutive subjects underwent optic nerve head imaging with HRT-3 and HD-OCT during a single visit. The vertical dimensions of the disc and cup were measured by slit-lamp examination using an eyepiece graticule. Bland-Altman plots evaluated the agreement in the VCDR obtained by the 2 instruments and clinical grading. RESULTS: We found a significant trend for the difference in VCDR measured clinically and with HRT and HD-OCT (P<0.001 for both). The mean VCDR differed significantly between clinical measurement and that evaluated by HRT and HD-OCT, respectively (0.40 ± 0.12 vs. 0.37 ± 0.21 and 0.40 ± 0.12 vs. 0.50 ± 0.14, P<0.001 for both), with significantly poor correlation (r(2)=0.35 and 0.34, P<0.001 for both). CONCLUSIONS: In general, there is poor correlation and a lack of agreement of VCDR measured using HRT-3, HD-OCT, and clinical grading. HD-OCT has somewhat better agreement with clinical measurements of VCDR. Compared with clinical grading, HD-OCT tended to overestimate VCDR, whereas HRT-3 tended to underestimate it.

Meta-analysis of Genome-Wide Association Studies Identifies Novel Loci Associated With Optic Disc Morphology.

Primary open-angle glaucoma is the most common optic neuropathy and an important cause of irreversible blindness worldwide. The optic nerve head or optic disc is divided in two parts: a central cup (without nerve fibers) surrounded by the neuroretinal rim (containing axons of the retinal ganglion cells). The International Glaucoma Genetics Consortium conducted a meta-analysis of genome-wide association studies consisting of 17,248 individuals of European ancestry and 6,841 individuals of Asian ancestry. The outcomes of the genome-wide association studies were disc area and cup area. These specific measurements describe optic nerve morphology in another way than the vertical cup-disc ratio, which is a clinically used measurement, and may shed light on new glaucoma mechanisms. We identified 10 new loci associated with disc area (CDC42BPA, F5, DIRC3, RARB, ABI3BP, DCAF4L2, ELP4, TMTC2, NR2F2, and HORMAD2) and another 10 new loci associated with cup area (DHRS3, TRIB2, EFEMP1, FLNB, FAM101, DDHD1, ASB7, KPNB1, BCAS3, and TRIOBP). The new genes participate in a number of pathways and future work is likely to identify more functions related to the pathogenesis of glaucoma.

The relationship between quality of life and adherence to medication in glaucoma patients in Singapore.

PURPOSE: (i) To evaluate the medication adherence rate of glaucoma patients in Singapore. (ii) To evaluate patients' quality of life status. (iii) To explore the factors related to patients' nonadherence to medication. PATIENTS AND METHODS: A cross-sectional, prospective study, using interviewer-administered survey questionnaires. A total of 314 patients were interviewed altogether, of which 175 (55.7%) were male and 139 (44.3%) were female. (i) Patients' medication adherence was assessed using the Reported Adherence to Medication scale. (ii) Patients' beliefs about glaucoma and treatment were evaluated using the Brief Illness Perception Questionnaire and the Beliefs about Medicine-Specific Questionnaire. (iii) Patients' quality of life was evaluated using Glaucoma Symptom Scale and The Glaucoma Quality of Life-15 questionnaire. RESULTS: Sixty-two (19.7%) patients reported themselves to be adherent to their medication. Male patients (P=0.044) and smokers (P=0.002) were more likely to be nonadherent to their medication regimen. Nonadherent patients were more likely to have (i) more concerns about their glaucoma medications (P=0.000); (ii) less belief in the effects of their medications (P=0.026); (iii) a lower quality of life (higher score of GQOL-15, P=0.014); (iv) less symptoms from their glaucoma (lower score of Glaucoma Symptom Scale, P=0.026); and (v) more effect on their lives from glaucoma (P=0.01). CONCLUSIONS: The full-adherence rate is low among glaucoma patients. Having less belief in the need for and more concerns about their medication are the 2 factors associated with nonadherence. In the future, effective strategies should be explored to improve patients' beliefs. Nonadherence has an association with decreased quality of life. Strategies to improve adherence will need to deal with these areas.

Micropulse versus continuous wave transscleral diode cyclophotocoagulation in refractory glaucoma: a randomized exploratory study.

BACKGROUND: The aim of this study was to compare the efficacy and safety of micropulse and continuous wave diode transscleral cyclophotocoagulation in refractory glaucoma. DESIGN: Randomized, comparative, exploratory study in a tertiary hospital setting. PARTICIPANTS: Patients with refractory, end-stage glaucoma. METHODS: Forty-eight patients were randomized to either treatment. The intraocular pressure, visual acuity, number of medicines and repeat treatment were monitored for 18 months. Complications that include visual acuity decline, prolonged anterior chamber inflammation, phthisis bulbi, scleral thinning and ocular pain were noted. MAIN OUTCOME MEASURE: Intraocular pressure between 6 and 21 mmHg and at least a 30% reduction with or without anti-glaucoma medications after 18 months. RESULTS: A successful primary outcome was achieved in 75% of patients who underwent micropulse cyclophotocoagulation and 29% of patients who received continuous wave cyclophotocoagulation after 12 months (P < 0.01). At 18 months, successful outcome was 52% and 30% (P = 0.13), respectively. The mean intraocular pressure was reduced by 45% in both groups (P = 0.70) from a baseline of 36.5 mmHg and 35.0 mmHg (P = 0.50) after 17.5 ± 1.6 months (range 16-19) follow up. No significant difference in retreatment rates or number of intraocular pressure lowering medications was noted. The ocular complication rate was higher in continuous wave treated eyes (P = 0.01). CONCLUSION: Diode transscleral cyclophotocoagulation in both micropulse and continuous modes was effective in lowering intraocular pressure. The micropulse mode provided a more consistent and predictable effect in lowering intraocular pressure with minimal ocular complications.

Facial Scanning With a Digital Camera: A Novel Way of Screening for Primary Angle Closure.

PURPOSE: We hypothesize that patients with primary angle closure (PAC) have common significant facial characteristics that set them apart from an age-matched, sex-matched, and race-matched control population. The primary objective of this study was to test whether a 3-dimensional (3D) camera could pick up these differences in order to differentiate PAC patients from controls. PATIENTS: A total of 55 patients with PAC and 38 controls were included in the study. MATERIALS AND METHODS: Cases and controls had their facial photographs taken using a 3-dimensional digital camera (3dMdFace System). The facial features in the captured photographs were analyzed using a computer software (Neural Network Toolbox). A regression formula was devised to show whether these facial parameters could be used to distinguish between patients and controls. RESULTS: Thirteen facial parameters were measured, and using a regression formula and neural network classification we were able to mathematically distinguish patients from controls using this method of screening. CONCLUSIONS: PAC patients have distinct facial features that may be differentiated from those of normal individuals mathematically using 3D photography. There is potential for this 3D facial scanning technology in screening for PAC in the general population.

Meta-analysis of genome-wide association studies identifies novel loci that influence cupping and the glaucomatous process.

Glaucoma is characterized by irreversible optic nerve degeneration and is the most frequent cause of irreversible blindness worldwide. Here, the International Glaucoma Genetics Consortium conducts a meta-analysis of genome-wide association studies of vertical cup-disc ratio (VCDR), an important disease-related optic nerve parameter. In 21,094 individuals of European ancestry and 6,784 individuals of Asian ancestry, we identify 10 new loci associated with variation in VCDR. In a separate risk-score analysis of five case-control studies, Caucasians in the highest quintile have a 2.5-fold increased risk of primary open-angle glaucoma as compared with those in the lowest quintile. This study has more than doubled the known loci associated with optic disc cupping and will allow greater understanding of mechanisms involved in this common blinding condition.

Can an inexperienced observer accurately plot disc contours using Heidelberg retinal Tomograph?

OBJECTIVE: To examine the reliability of inexperienced observers in plotting optic disc contours on Heidelberg retinal tomography images before and after training. DESIGN: Observational study. PARTICIPANTS: One hundred eyes that were randomly selected from the Singapore Indian Eye Study. METHODS: Both eyes of subjects were imaged with Heidelberg Retina Tomograph 3 (HRT-3; Heidelberg Engineering, Heidelberg, Germany). Optic disc contours were plotted on the same images by 2 new observers on 2 separate occasions, before and after 2-hour standardized training on the skills and tools available to accurately identify and delineate optic disc contours. These plottings were compared with an experienced, trained glaucoma expert (gold standard). Agreement and variability were analyzed by interclass correlation tests and Bland-Altman plots. RESULTS: A total of 182 images (18 excluded because of poor quality) from 89 Indian subjects were included. The mean age was 53.27 ± 7.25 years and 54.8% were male. There was moderate-to-high agreement between pretraining (both new observers) and experienced observer's results (interclass correlation values range, 0.76-0.99). The interclass correlation improved for all the HRT-3 parameters after the 2 new observers were adequately trained. Comparing the interclass correlation values before and after training, the differences for mean retinal nerve fibre layer thickness for Observer 1 and all the HRT-3 parameters for Observer 2 were statistically significant. CONCLUSIONS: This study shows that it is easy to train a new inexperienced observer to plot optic disc contours on HRT images, which translates into improved and acceptable interobserver variability and agreement.

ABCC5, a gene that influences the anterior chamber depth, is associated with primary angle closure glaucoma.

Anterior chamber depth (ACD) is a key anatomical risk factor for primary angle closure glaucoma (PACG). We conducted a genome-wide association study (GWAS) on ACD to discover novel genes for PACG on a total of 5,308 population-based individuals of Asian descent. Genome-wide significant association was observed at a sequence variant within ABCC5 (rs1401999; per-allele effect size =  -0.045 mm, P = 8.17 × 10(-9)). This locus was associated with an increase in risk of PACG in a separate case-control study of 4,276 PACG cases and 18,801 controls (per-allele OR = 1.13 [95% CI: 1.06-1.22], P = 0.00046). The association was strengthened when a sub-group of controls with open angles were included in the analysis (per-allele OR = 1.30, P = 7.45 × 10(-9); 3,458 cases vs. 3,831 controls). Our findings suggest that the increase in PACG risk could in part be mediated by genetic sequence variants influencing anterior chamber dimensions.

Laser iridotomy and the corneal endothelium: a systemic review.

This study aims to systemically review the effect of laser iridotomy on the corneal endothelium. Searches were performed for studies that either compared corneal endothelial cell density/count, corneal thickness and morphology pre- and postiridotomy, or evaluated the postiridotomy development of corneal decompensation. There were 26 eligible studies. Our review shows that the effect of laser iridotomy on the corneal endothelium has been investigated with varying results. Although it has been demonstrated to be a relatively safe procedure, there is still the potential long-term risk of corneal decompensation, for which a corneal transplantation may be indicated eventually. The longest interval between laser iridotomy and corneal decompensation reported was 8 years. Mechanisms proposed for endothelial damage include direct focal injury, thermal damage, mechanical shock waves, iris pigment dispersion, transient rise in intraocular pressure, inflammation, turbulent aqueous flow, time-dependent shear stress on endothelium, chronic breakdown of blood-aqueous barrier and damage from bubbles that settled onto the endothelium. Inherent risk factors identified were iridotrabecular contact, current or prior acute angle closure, pigmented irides, small iris-to-endothelium distance, pre-existing endothelial disease and diabetes. Intervention-related risk factors include laser type, delivery and quantity. The significance of the risk factors and their direct association with the development of corneal decompensation remain to be determined. Understanding these risk factors may allow physicians to counsel their patients better. They may offer opportunities for preventive strategies, allowing us to ensure that a procedure performed to prevent disease progression and visual loss does not cause further morbidity.

Pretreatment anterior segment imaging during acute primary angle closure: insights into angle closure mechanisms in the acute phase.

OBJECTIVE: To describe anterior segment optical coherence tomography (ASOCT) parameters during acute primary angle closure (APAC) before therapeutic interventions and comparative analyses of biometric parameters of APAC eyes with fellow eyes. DESIGN: Prospective, comparative case series. PARTICIPANTS: Thirty-one consecutive patients with APAC. METHODS: All patients underwent ASOCT imaging of both eyes during the attack, before therapeutic interventions were administered. Custom software was used to measure anterior chamber depth (ACD), anterior chamber area (ACA), anterior chamber volume (ACV), iris curvature (I-Curv), iris area (I-Area), lens vault (LV), and angle opening distance (AOD750), trabecular iris space area (TISA750), and iris thickness (IT750) at 750 µm from the scleral spur. Multivariate logistic regression modeling using forward selection was used to determine the most important biometric variables associated with APAC compared with the fellow eye during the attack. MAIN OUTCOME MEASURES: Anterior segment biometric parameters associated with APAC. RESULTS: The mean age of the patients was 60.9±7.5 years, and 11 patients (35.5%) were male. The mean intraocular pressure was 3.8±9.2 mmHg in the APAC eye and 4.2±4.3 mmHg in the fellow eye before treatment (P <0.001). After adjustment for pupil diameter, APAC eyes had smaller ACD, ACA, ACV, I-Curv (all P <0.001), AOD750 (P = 0.037), TISA750 (P = 0.043), I-Area (P = 0.027), and IT750 (P = 0.002) and larger LV (P = 0.041) than fellow eyes. An optimal model consisting of 3 variables (pupil diameter, ACD, and I-Curv) explained 36.7% of the variance in APAC occurrence, with ACD accounting for 18.1% and I-Curv accounting for 14.1% of this variance. CONCLUSIONS: Shallower ACD and smaller I-Curv were the 2 main anterior segment biometric parameters associated with APAC during the attack. These findings present new insights into the anterior segment biometric parameters of APAC and fellow eyes before therapeutic interventions. Anatomic changes in the anterior segment explained only about one third of the variance in APAC occurrence, and the role of nonanatomic factors require further investigation.