Two new parameters to assess anterior chamber angle for SS-OCT images

In this paper, we propose an automatic quantitative assessment method of the anterior chamber angle of the eye using swept source optical coherence tomography (SS-OCT) images. The angle structure was assessed by two new parameters: 1) mean of continuous measurement of angle opening distance (mAOD) centered on Schwalbe's line; and 2) area of the anterior chamber (AAC). In this research, two hundred and fifty-two SS-OCT images were analyzed. The measurements of open and closed angle in SS-OCT images were compared with that of Schwalbe's line based single angle assessment (AOD_sl, ARA_sl). Our continuous based AOD measurement shows over 93% correlation with the single based AOD angle assessment but provides a more reliable and accurate measurement for open and closed angle SS-OCT images. These newly proposed parameters give a better representation of the angle width for capturing the nature of the angle dynamics involved in different forms of angle closure or open angle glaucoma

Optical coherence tomography angiography of the macula and optic nerve head: microvascular density and test-retest repeatability in normal subjects

Abstract Background Despite the potential usefulness of optical coherence tomography angiography in retinal and optic disc conditions, the reliability of the imaging modality remains unclear. This study set out to measure the microvascular density of macula and optic disc by mean of optical coherence tomography angiography and report the repeatability of the vessel density measurements. Methods Cross sectional observational cohort study. Subjects with normal eyes were recruited. Two sets of optical coherence tomography angiography images of macula and optic nerve head were acquired during one visit. Novel in-house developed software was used to count the pixels in each images and to compute the microvessel density of the macula and optic disc. Data were analysed to determine the measurement repeatability. Results A total of 176 eyes from 88 consecutive normal subjects were recruited. For macular images, the mean vessel density at superficial retina, deep retina, outer retina and choriocapillaries segment was OD 0.113 and OS 0.111, OD 0.239 and OS 0.230, OD 0.179 and OS 0.164, OD 0.237 and OS 0.215 respectively. For optic disc images, mean vessel density at vitreoretinal interface, radial peripapillary capillary, superficial nerve head and disc segment at the level of choroid were OD 0.084 and OS 0.085, OD 0.140 and OS 0.138, OD 0.216 and OS 0.209, OD 0.227 and OS 0.236 respectively. The measurement repeatability tests showed that the coefficient of variation of macular scans, for right and left eyes, ranged from 6.4 to 31.1% and 5.3 to 59.4%. Likewise, the coefficient of variation of optic disc scans, for right and left eyes, ranged from 14.3 to 77.4% and 13.5 to 75.3%. Conclusions Optical coherence tomography angiography is a useful modality to visualise the microvasculature plexus of macula and optic nerve head. The vessel density measurement of macular scan by mean of optical coherence tomography angiography demonstrated good repeatability. The optic disc scan, on the other hand, showed a higher coefficient of variation indicating a lower measurement repeatability than macular scan. Interpretation of optical coherence tomography angiography should take into account test-retest repeatability of the imaging system. Trial registration National Healthcare Group Domain Specific Review Board (NHG DSRB) Singapore. DSRB Reference: 2015/00301

Impact of Community Eye Clinics (CEC) on Specialist Eye Clinic Referrals

Community Eye Clinics (CEC) increase accessibility of specialist ophthalmic services in the community, reducing demand for tertiary eye services. This paper aims to evaluate the impact of CEC on first-visit referrals from Hougang Polyclinic (HOU) to Tan Tock Seng Hospital Ophthalmology Specialist Outpatient Clinic (SOC). A retrospective analysis was performed on first-visit referrals from Hougang Polyclinic (HOU) to Tan Tock Seng Hospital Ophthalmology Specialist Outpatient Clinic (SOC) over a similar 3-months period before and after the introduction of CEC in August 2018 (1 January to 31 March in 2018 and 2019, respectively). Data pertaining to patients’ presenting complaints, referral reasons, final diagnoses, follow-up plans, and need for ophthalmic intervention were obtained. We included 978 patients in our study. There was a 27.5% reduction in the number of first-visit referrals seen at SOC after the establishment of CEC. Patients were more likely to be referred on to sub-specialty eye clinics (10.8% vs. 12.9%, p= p = .304) and receive more ophthalmic interventions (15% vs. 16.3%, p = .066) than prior to CEC. The CEC provides greater accessibility to eye care within the community. Optometrists are upskilled to manage patients with stable eye conditions, whilst eye specialists can provide timely care to the SOC for patients with more severe eye conditions.</p

Genome-wide association analyses identify three new susceptibility loci for primary angle closure glaucoma.

Primary angle closure glaucoma (PACG) is a major cause of blindness worldwide. We conducted a genome-wide association study including 1,854 PACG cases and 9,608 controls across 5 sample collections in Asia. Replication experiments were conducted in 1,917 PACG cases and 8,943 controls collected from a further 6 sample collections. We report significant associations at three new loci: rs11024102 in PLEKHA7 (per-allele odds ratio (OR)=1.22; P=5.33×10(-12)), rs3753841 in COL11A1 (per-allele OR=1.20; P=9.22×10(-10)) and rs1015213 located between PCMTD1 and ST18 on chromosome 8q (per-allele OR=1.50; P=3.29×10(-9)). Our findings, accumulated across these independent worldwide collections, suggest possible mechanisms explaining the pathogenesis of PACG

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. PLoS Genet 2014 Mar 6; 10(3):e1004089

Genome-wide association analyses identify three new susceptibility loci for primary angle closure glaucoma

10.1038/ng.2390Nature Genetics44101142-1146NGEN

Association analysis between <i>ABCC5</i> rs1401999 and primary angle closure glaucoma in all chip-typed sample collections (top panel), de-novo genotyped sample collections (middle panel), and PACG cases and clinically certified controls with open angles (bottom panel).

<p>MAF case: Minor allele frequency in PACG cases.</p><p>MAF control: Minor allele frequency in controls.</p><p>OR: Odds ratio.</p><p><i>P</i>: <i>P</i>-value for association with PACG.</p><p>I²: I-squared index for between-collection heterogeneity.</p><p>* Results here are presented based on raw minor allele frequency counts without further adjustment.</p>†<p>PACG patients were recruited from the Beijing Tongren Hospital and controls were recruited from the Handan Eye Study (HES), a population-based study of eye disease in rural Chinese aged 30 years and over.</p