Seng Chee Loon

Quantitative evaluation of anterior chamber parameters using anterior segment optical coherence tomography in primary angle closure mechanisms

Background:  To evaluate different mechanisms of primary angle closure and to quantify anterior chamber parameters in these mechanisms using anterior segment optical coherence tomography in an Asian population.

Primary external dacryocystorhinostomy versus primary endonasal dacryocystorhinostomy: a review

This paper aims to compare the efficacy, mean operative time and adverse effects of primary external dacryocystorhinostomy (DCR) versus primary endonasal DCR in treating acquired nasolacrimal duct obstruction. Searches were performed for studies comparing the two procedures. Two reviewers independently extracted data from 14 eligible studies. A random effects model was used to analyse the studies. Outcome measures were defined as patency of the nasolacrimal canal and mean operative time, and adverse effects as cutaneous scarring and bleeding. Both procedures were comparable in efficacy in terms of full success, partial success and anatomic patency. Subgroup analysis showed no significant difference between prospective and retrospective studies as well as between non‐laser endonasal DCR versus external DCR and laser endonasal DCR versus external DCR. Endonasal DCR had a significantly shorter mean operative duration, be it laser endonasal DCR (mean difference: 37.65 min, 95% confidence intervals: 3.54–71.75 min, P: 0.03) or non‐laser endonasal DCR (mean difference: 19.22 min, 95% confidence intervals: 2.15–36.28 min, P: 0.03). The odds of postoperative bleeding was not significantly different between the two procedures, whereas postoperative cutaneous scarring was unique to external DCR and occurred in 50 out of 402 (12.44%) external DCRs recorded. Endonasal DCR has comparable success rates with external DCR and has a shorter operative time and no cutaneous scar. However, drawbacks include the steep learning curve and higher costs.

Outcomes following acute primary angle closure in an Asian population

Background:  Data regarding development of primary angle closure glaucoma (PACG) following acute primary angle closure (APAC) is conflicting. This study looks at outcomes after an APAC episode with a secondary aim to identify any risk factors that could predict progression to PACG.

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.

A Major Review of Antimetabolites in Glaucoma Therapy

Antimetabolites have been used in combination with filtering surgery to improve surgical results for more than 10 years. Based on research published since the introduction of antimetabolites right up to date, we discuss the various forms of antimetabolites that have been used, including drugs and irradiation. Among the drugs used, mitomycin C and 5-fluorouracil are the most prominent. We discuss the background of these agents, the progress in the use of antimetabolites and the research done on these drugs. These agents have been used both intra-operatively and perioperatively. We discuss the indications for their use, their mode of action, the techniques of usage, their variations as well as the complications and the treatment of complications.

Lens Opacities Classification System III: Cataract grading variability between junior and senior staff at a Singapore hospital

PURPOSE: To test the reliability of the Lens Opacities Classification System III (LOCS III) cataract grading between observers at different levels of ophthalmology experience. SETTING: Ophthalmology Department, National University Hospital, Singapore, Singapore. METHODS: In this comparative study, a non‐ophthalmology trainee, a basic ophthalmology trainee, and an ophthalmology consultant graded cataracts in 28 patients preoperatively. The observers had a meeting to discuss their interpretations of the LOCS III manual to standardize the grading system and then graded 37 additional patients. RESULTS: There was a statistically significant increase in inter‐observer agreement in all 3 LOCS III categories after standardization of the LOCS III system. The κ values after standardization fell in the moderate (0.41 to 0.60) to substantial (0.61 to 0.80) range. There was no statistically significant relationship between the observers experience and the κ values. CONCLUSIONS: There was an increase in inter‐observer agreement in all categories after standardization between operators.

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

The aim of this study was to compare the efficacy and safety of micropulse and continuous wave diode transscleral cyclophotocoagulation in refractory glaucoma.

Prevalence and risk factors of ocular trauma in an urban south‐east Asian population: the Singapore Malay Eye Study

Purpose:  To describe the prevalence and risk factors of ocular trauma in an urban Asian population.

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.

Quantitative assessment of changes in trabeculectomy blebs after laser suture lysis using anterior segment coherence tomography

PurposeTo quantify changes in bleb morphology after laser suture lysis (LSL) using anterior segment optical coherence tomography (AS-OCT). Patients and MethodsThis was a prospective observational case series of patients who underwent trabeculectomy surgery with mitomycin-C and required subsequent LSL. Subjects were assessed before and immediately after LSL, and at 3 months after LSL. At each visit, a standardized cross-sectional AS-OCT image of the bleb was obtained, from which a masked observer measured bleb height (hB), cavity height (hC), wall cross sectional area (AW), cavity cross sectional area (AC), and bleb cross sectional area (AB) using custom software. ResultsTwenty-five subjects (25 eyes) were examined. LSL was performed at a mean of 21.5±16.3 days after trabeculectomy. Immediately after LSL, there was a significant increase in mean hB (P=0.026) and mean hC (P=0.45) from pre-LSL. At 3 months after LSL, there was a significant increase in mean hB (P=0.003), mean AC (P=0.047), and mean AB (P=0.006) as compared with before LSL. Increase in hB and hC immediately after LSL was predictive of outcome at month 3. ConclusionsAS-OCT was able to quantify changes in bleb morphology after LSL, some of which were predictive of eventual outcome.