ORCID Profile
0000-0002-6474-5293
Current Organisations
Duke-NUS Medical School
,
Singapore Eye Research Institute
,
Singapore National Eye Center
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Publisher: Elsevier BV
Date: 11-2015
DOI: 10.1016/J.OPHTHA.2015.06.052
Abstract: To determine the prevalence of age-related cataract and its ancestral and socioeconomic risk factors in a multi-ethnic Asian population. Population-based, cross-sectional study. A total of 10 033 adults (3353 Chinese, 3280 Malays, and 3400 Indians) aged >40 years in the Singapore Epidemiology of Eye Diseases Study. Study participants were invited for a structured interview and received a standardized comprehensive eye examination. Digital lens photographs were taken from eyes of each participant and graded for nuclear, cortical, and posterior subcapsular (PSC) cataract, following the Wisconsin Cataract Grading System. Prevalence data were compared with the Blue Mountains Eye Study (BMES) in Australia. Information on medical and lifestyle factors was collected using questionnaires and blood s les. To increase the precision of racial definition, genetic ancestry was derived from genome-wide single nucleotide polymorphism markers using principal component analysis. Regression models were used to investigate the association of cataract with socioeconomic factors (education and income) and genetic ancestry. Age-related cataract. A total of 8750 participants (94.0%) had gradable lens photographs. The age-standardized prevalence of cataract surgery in Chinese (16.0%), Malays (10.6%), and Indians (20.2%) was higher than in white subjects (4.1%). We found the age-standardized cataract prevalence in Chinese (30.4%), Malays (37.8%), and Indians (33.1%) was higher than in whites (18.5%). Cataract was 1.5 to 2 times more common in Asians and began 10 years earlier than in white subjects. Malays had significantly higher age-standardized prevalence of nuclear, cortical, and PSC cataract than Chinese (P<0.001). The severity of nuclear, cortical, and PSC cataract was significantly correlated with genetic ancestry in our South East Asian population. Less education and lower income were associated with cataract for Chinese and Indians but not Malays. The presence of visual impairment associated with cataract was higher in people aged ≥60 years and Malays. We showed that people of different Asian ethnicities had a higher prevalence and earlier age of onset of cataract than Europeans. People of Malay ancestry have a greater severity for all cataract subtypes than people of Chinese ancestry. Education and income were associated with cataract for certain Asian subgroups.
Publisher: Elsevier BV
Date: 10-2014
DOI: 10.1016/J.OPHTHA.2014.04.041
Abstract: To determine the ethnic differences in the distribution of intraocular pressure (IOP) and central corneal thickness (CCT) in a multi-ethnic Asian population by self-reported ethnicity and genetic ancestry. Population-based, cross-sectional study. A total of 10 033 adults (3353 Chinese, 3280 Malays, and 3400 Indians) aged >40 years. Participants underwent standardized systemic and ocular examinations and interviewer-administered questionnaires for risk factor assessment. The IOP readings were obtained by Goldmann applanation tonometry (Haag-Streit, Konig, Switzerland) before pupil dilation. The CCT was measured with ultrasound pachymetry. Genetic ancestry was derived using principal component (PC) analysis. Regression models were used to investigate the association of IOP and CCT with potential risk factors and genetic ancestry. Intraocular pressure and CCT. After excluding participants with a history of glaucoma surgery or medication, refractive surgery, corneal edema, or corneal dystrophy, IOP and CCT readings were available for 3251 Chinese, 3232 Malays, and 3317 Indians. The mean IOP readings in the Chinese, Malay, and Indian participants were 14.3±3.1, 15.3±3.7, and 15.8±2.9 mmHg, respectively (P < 0.001). The prevalence of participants with IOP ≥21 mmHg was 2.6% in Chinese, 6.2% in Malays, and 4% in Indians (P < 0.001). In the multivariate regression analysis, the Malay and Indian participants on average had 0.81 and 1.43 mmHg higher IOP levels, respectively, than Chinese (P < 0.001). The mean CCT reading was 552.3±33.4 μm in Chinese, 540.9±33.6 μm in Malays, and 540.4±33.6 μm in Indians (P < 0.001). The percentage of participants with CCT <555 μm was 52.8% in Chinese, 68.5% in Malays, and 66.2% in Indians (P < 0.001). The IOP and CCT levels are significantly correlated with genetic ancestry in our South East Asian population. Chinese have the thickest CCT but lowest IOP among the 3 major ethnic groups. In addition, there is a higher proportion of Malays with IOP ≥21 mmHg and CCT <555 μm compared with the Chinese or Indians. This disparity across ethnic groups should be taken into account by future studies investigating IOP and CCT as risk factors or diagnostic tests for glaucoma in Asian populations.
Publisher: BMJ
Date: 27-05-2020
DOI: 10.1136/BJOPHTHALMOL-2020-316111
Abstract: To compare the retinal vessel diameter measurements obtained from the swept-source optical coherence tomography angiography (OCTA Plex Elite 9000, Carl Zeiss Meditec, USA) and adaptive optics ophthalmoscope (AOO RTX1, Imagine Eyes, France). Fifteen healthy subjects, 67% women, mean age (SD) 30.87 (6.19) years, were imaged using OCTA and AOO by a single experienced operator on the same day. Each eye was scanned using two OCTA protocols (3×3 mm 2 and 9×9 mm 2 ) and two to five AOO scans (1.2×1.2 mm 2 ). The OCTA and AOO scans were scaled to the same pixel resolution. Two independent graders measured the vessel diameter at the same location on the region-of-interest in the three coregistered scans. Differences in vessel diameter measurements between the scans were assessed. The inter-rater agreement was excellent for vessel diameter measurement in both OCTA protocols (ICC=0.92) and AOO (ICC=0.98). The measured vessel diameter was widest from the OCTA 3×3 mm 2 (55.2±16.3 µm), followed by OCTA 9×9 mm 2 (54.7±14.3 µm) and narrowest by the AOO (50.5±15.6 µm p .001). Measurements obtained from both OCTA protocols were significantly wider than the AOO scan (OCTA 3×3 mm 2 : mean difference Δ=4.7 µm, p .001 OCTA 9×9 mm 2 : Δ=4.2 µm, p .001). For vessels µm, it appeared to be larger in OCTA 3×3 mm 2 scan than the 9×9 mm 2 scan (Δ=1.9 µm p=0.005), while vessels µm appeared smaller in OCTA 3×3 mm 2 scan (Δ=−1.3 µm p=0.009) The diameter of retinal vessels measured from OCTA scans were generally wider than that obtained from AOO scans. Different OCTA scan protocols may affect the vessel diameter measurements. This needs to be considered when OCTA measures such as vessel density are calculated.
Publisher: Elsevier BV
Date: 12-2013
DOI: 10.1016/J.EXPNEUROL.2013.09.007
Abstract: Pattern recognition has been used for the complete and statistically rigid classification of retinal neurons in vertebrates such as the adult cat, primate, rat and goldfish. Here, we label the mouse retina with antibodies against seven amino acids and use pattern recognition to characterize distinct retinal neurochemical cell classes based on their unique amino acid signatures. We followed the development of the cell classes in the X-inactivation transgenic mouse expressing the lacZ reporter gene on one X-chromosome. This mouse allows clonally related cells to be identified through differential β-galactosidase activity due to random X-chromosome inactivation. Pattern recognition analysis partitioned the retina into nine neuronal classes at birth, increasing to 19 classes at eye opening and 26 classes by adulthood. Emergence of new cell classes was partly attributed to new neuron types and partly to the splitting of classes from early ages from refinement of their amino acid profiles. All six GABAergic amacrine cell classes and most ganglion cell classes appeared by P7 whilst all the glycinergic amacrine cell classes did not appear till adulthood. Separable bipolar cell classes were not detected till eye opening. Photoreceptor cell classes were detected at P3 but inner and outer segments did not form separable classes until adulthood. More importantly, we show that cells which share common amino acid profiles also shared cell dispersion patterns. GABAergic amacrine cell classes with conventional and displaced counterparts transgressed clonal boundaries whereas GABAergic amacrine cell classes found exclusively in the inner nuclear layer and all glycinergic amacrine cell classes did not transgress. Ganglion cells displayed both dispersion patterns. This study provides a comprehensive neurochemical atlas of the developing mouse retina, tracking the amino acid levels within distinct neuronal populations and highlighting unique migratory patterns within subpopulations of inner retinal neurons.
Publisher: MDPI AG
Date: 25-11-2022
DOI: 10.3390/NU14235021
Abstract: Diabetic retinopathy (DR) is a common microvascular complication of diabetes mellitus. The evidence connecting dietary intake and DR is emerging, but uncertain. We conducted a systematic review to comprehensively summarize the current understanding of the associations between dietary consumption, DR and diabetic macular edema (DME). We systematically searched PubMed, Embase, Medline, and the Cochrane Central Register of Controlled Trials between January 1967 to May 2022 for all studies investigating the effect of diet on DR and DME. Of the 4962 articles initially identified, 54 relevant articles were retained. Our review found that higher intakes of fruits, vegetables, dietary fibers, fish, a Mediterranean diet, oleic acid, and tea were found to have a protective effect against DR. Conversely, high intakes of diet soda, caloric intake, rice, and choline were associated with a higher risk of DR. No association was seen between vitamin C, riboflavin, vitamin D, and milk and DR. Only one study in our review assessed dietary intake and DME and found a risk of high sodium intake for DME progression. Therefore, the general recommendation for nutritional counseling to manage diabetes may be beneficial to prevent DR risk, but prospective studies in erse diabetic populations are needed to confirm our findings and expand clinical guidelines for DR management.
Publisher: Informa UK Limited
Date: 05-2013
DOI: 10.1111/CXO.12015
Abstract: Advances in basic retinal anatomy, genetics, biochemical pathways and neurochemistry have not only provided a better understanding of retinal function but have also allowed us to link basic science to retinal disease. The link with disease allowed measures to be developed that now provide an opportunity to intervene and slow down or even restore sight in previously 'untreatable' retinal diseases. One of the critical advances has been the understanding of the retinal amino acid neurotransmitters, related amino acids, their metabolites and functional receptors. This review provides an overview of amino acid localisation in the retina and ex les of how retinal anatomy and amino acid neurochemistry directly links to understanding retinal disease. Also, the implications of retinal remodelling involving amino acid (glutamate) receptors are outlined in this review and insights are presented on how understanding of detrimental and beneficial retinal remodelling will provide better outcomes for patients using strategies for the preservation or restoration of vision. An internet-based database of retinal images of amino acid labelling patterns and other amino acid-related images in health and disease is located at www.aminoacidimmunoreactivity.com.
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.OPHTHA.2016.06.034
Abstract: To determine the association of iris surface features with iris volume change after physiologic pupil dilation in adults. Cross-sectional observational study. Chinese adults aged ≥ 50 years without ocular diseases. Digital iris photographs were taken from eyes of each participant and graded for crypts (by number and size) and furrows (by number and circumferential extent) following a standardized grading scheme. Iris color was measured objectively, using the Commission Internationale de l'Eclairage (CIE) L* color parameter (higher value denoting lighter iris). The anterior segment was imaged by swept-source optical coherence tomography (SS-OCT) (Casia Tomey, Nagoya, Japan) under bright light and dark room conditions. Iris volumes in light and dark conditions were measured with custom semiautomated software, and the change in iris volume was quantified. Associations of the change in iris volume after pupil dilation with underlying iris surface features in right eyes were assessed using linear regression analysis. Iris volume change after physiologic pupil dilation from light to dark condition. A total of 65 Chinese participants (mean age, 59.8±5.7 years) had gradable data for iris surface features. In light condition, higher iris crypt grade was associated independently with smaller iris volume (β [change in iris volume in millimeters per crypt grade increment] = -1.43, 95% confidence interval [CI], -2.26 to -0.59 P = 0.001) and greater reduction of iris volume on pupil dilation (β [change in iris volume in millimeters per crypt grade increment] = 0.23, 95% CI, 0.06-0.40 P = 0.010), adjusting for age, gender, presence of corneal arcus, and change in pupil size. Iris furrows and iris color were not associated with iris volume in light condition or change in iris volume (all P > 0.05). Although few Chinese persons have multiple crypts on their irides, irides with more crypts were significantly thinner and lost more volume on pupil dilation. In view that the latter feature is known to be protective for acute angle-closure attack, it is likely that the macroscopic and microscopic composition of the iris is a contributing feature to angle-closure disease.
Publisher: BMJ
Date: 18-03-2016
DOI: 10.1136/BJOPHTHALMOL-2015-308256
Abstract: To characterise the association of iris surface features (crypts, furrows and colour) with iris volume and curvature assessed by swept-source optical coherence tomography (SSOCT) in Asian eyes. Iris crypts (by number and size) and furrows (by number and circumferential extent) were graded from iris photographs. Iris colour was measured by a customised algorithm written on MATLAB (MathWorks, Natick, Massachusetts, USA). The iris was imaged by SSOCT (SS-1000, CASIA, Tomey, Nagoya, Japan). The associations of surface features with iris parameters were analysed using a generalised estimating equation. A total of 1704 subjects (3297 eyes) were included in the analysis. The majority was Chinese (86.4%), and 63.2% were females, and their mean age (±SD) was 61.4±6.6 years. After adjusting for age, sex, ethnicity, pupil size and corneal arcus, higher iris crypt grade was independently associated with smaller iris volume (β=-0.54, p<0.001), whereas darker irides and higher iris furrow grade were associated with larger iris volume (β=-0.041, p<0.001) and (β=0.233, p<0.001), respectively. Lighter coloured irides with more crypts and/or more furrows were also associated with less convexity (crypts: β=-0.003, p=0.03 furrows: β=-0.004, p=0.007 and colour: β=-0.001, p=0.005). Iris surface features were highly correlated with iris volume and curvature. Irides with more crypts have a smaller volume and darker irides with more furrows have a larger volume. Lighter irides with more crypts and/or furrows have less convexity.
Publisher: Wiley
Date: 04-06-2013
DOI: 10.1002/CNE.23307
Abstract: We studied the anatomical remodeling and gliosis of retinal Müller cells in the rd/rd mouse model of photoreceptor degeneration. A computational calculation of glutamine synthetase immunoreactivity was developed so we could specifically quantify changes in Müller cell anatomy between control mice (C57Bl/6) and the dystrophic strain. We found no change in the number of Müller cell somata between mice strains, indicating no cell proliferation as a function of development and degeneration. The retinal area occupied by the total Müller cell body (soma and processes) was significantly less in the rd/rd mouse retina compared with control mice. When only the outer retina was considered, we found rd/rd Müller cell processes were dramatically reduced during the cone phase of photoreceptor degeneration. However, at older ages an increase in Müller cell processes was seen. Conversely, glial fibrillary acidic protein (GFAP) expression showed a significant increase during cone degeneration followed by a reduction in older ages. Müller cell electrophysiology, particularly K(+) currents and membrane potential, was similar between rd/rd and control Müller cells during cone degeneration. Together, these results show that glial remodeling in the rd/rd retina follows separate phases-an initial conservative glial response involving the loss of Müller cells processes, hyperexpression of GFAP, and preservation of normal electrophysiology followed by an active growth of Müller cell processes, glial seal formation, and attenuation of GFAP expression after complete photoreceptor loss.
Publisher: American Medical Association (AMA)
Date: 05-2017
Publisher: BMJ
Date: 05-05-2020
DOI: 10.1136/BJOPHTHALMOL-2020-315985
Abstract: To identify factors that influence the diagnostic performance of circumpapillary retinal nerve fibre layer (RNFL) thickness measurements in the detection of primary open-angle glaucoma (POAG). 1592 eyes from 1076 healthy controls and 758 eyes from 502 patients with POAG underwent optical coherence tomography (OCT) imaging to assess RNFL parameters. Visual field (VF) mean deviation (MD) from standard automated perimetry was used to indicate severity in subjects with glaucoma. RNFL thickness significantly decreased with age (ρ=−0.10 to −0.16, p .001) and increased with spherical equivalent (SE) refractive error (ρ=0.23–0.29, p .001) in healthy and glaucoma groups but showed a significant reduction with SE (ρ=−0.20, p .001) in the temporal RNFL of healthy subjects. RNFL measurements significantly decreased with VF MD (ρ=0.08–0.53, p .05) in subjects with POAG. When healthy subjects and subjects with glaucoma were matched to subgroups within a factor, significant differences in area under the curve (AUC) between subgroups were only found with SE AUCs increased significantly with disease severity, particularly in the global, inferior and superior measurements (p .001). Overall, the diagnostic performance of the inferior and global RNFL measurements were found to be more resilient to different factors. Diagnostic accuracy in glaucoma was influenced by SE but could be mitigated by using controls with similar refractive characteristics. Increasing disease severity led to significantly better diagnostic accuracy. These factors should be considered when using OCT for glaucoma diagnosis in practice.
Publisher: American Medical Association (AMA)
Date: 08-2015
DOI: 10.1001/JAMAOPHTHALMOL.2015.1478
Abstract: Glaucoma can remain asymptomatic until a severe stage, resulting in a high prevalence of undiagnosed glaucoma worldwide. Asia accounts for 60% of the world's total glaucoma cases. To our knowledge, no epidemiological studies have assessed ethnic differences in undiagnosed glaucoma among various Asian subgroups. To determine the prevalence of, risk factors for, and visual features of undiagnosed primary glaucoma in a multiethnic Asian population. The Singapore Epidemiology of Eye Diseases Study is a population-based trial in which 3353 Chinese (2009-2011), 3280 Malays (2004-2006), and 3400 Indians (2007-2009) aged 40 to 80 years were invited for an eye examination, including visual field assessment, to establish glaucoma diagnosis. Participants with undiagnosed glaucoma (ie, answering no to whether they previously had been told by a physician that they had glaucoma, not using glaucoma medication, or not having undergone glaucoma surgery) were identified. Prevalence of, risk factors for, and visual features of undiagnosed glaucoma. Of 272 participants with primary glaucoma, 196 (72.1%) were previously undiagnosed. The overall prevalence of undiagnosed primary glaucoma was highest among Malays (2.65% 95% CI, 2.10%-3.31%), followed by Chinese (1.51% 95% CI, 1.13%-2.01%) and Indians (0.97% 95% CI, 0.64%-1.43%). In multivariable analysis, variables associated with higher risk of undiagnosed glaucoma were younger age (odds ratio [OR], 1.04 95% CI, 1.00-1.09 P = .04), Malay ethnicity (OR, 3.65 95% CI, 1.31-10.13 P = .01), presence of primary open-angle glaucoma (OR, 3.82 95% CI, 1.60-9.14 P = .003), absence of yearly eyeglass checks (OR, 9.29 95% CI, 3.43-25.21 P < .001), and lack of cataract surgery (OR, 4.19 95% CI, 1.68-10.48 P < .001). No patients were blind in both eyes. A mean (SD) of 4.1% (2.8%) (n = 8) of the newly diagnosed patients were blind in 1 eye, and a mean (SD) of 56.0% (7.2%) (n = 102) had noteworthy visual field damage (mean deviation worse than -6 dB) in at least 1 eye. The prevalence of undiagnosed primary glaucoma varied among ethnic populations in whom a mean (SD) of 49.0% (14.0%) (n = 24) of affected in iduals 50 to 59 years old already had clinically significant visual field loss. Such data may assist policymakers in implementing cost-effective public health interventions to reduce the effect of blindness associated with undiagnosed glaucoma.
Publisher: Springer Science and Business Media LLC
Date: 18-02-2020
DOI: 10.1038/S41598-020-59792-9
Abstract: We evaluated the changes in visual field mean deviation (VF MD) and retinal nerve fibre layer (RNFL) thickness in glaucoma patients undergoing trabeculectomy. One hundred patients were examined with VF and spectral-domain optical coherence tomography (OCT) before trabeculectomy and 4 follow-up visits over one year. Linear mixed models were used to investigate factors associated with VF and RNFL. VF improved during the first 3 months of follow-up (2.55 ± 1.06 dB/year) and worsened at later visits (−1.14 ± 0.29 dB/year). RNFL thickness reduced by −4.21 ± 0.25 µm/year from 1st month of follow-up. Eyes with an absence of initial VF improvement (β = 0.64 0.30–0.98), RNFL thinning (β = 0.15 0.08–0.23), increasing intraocular pressure (IOP β = −0.11 −0.18 to −0.03) and severe glaucoma (β = −10.82 −13.61 to −8.02) were associated with VF deterioration. Eyes with VF deterioration (β = 0.19 0.08–0.29), increasing IOP (β = −0.09 −0.17 to −0.01), and moderate (β = −6.33 −12.17 to −0.49) or severe glaucoma (β = −19.58 −24.63 to −14.52) were associated with RNFL thinning. Changes in RNFL structure and function occur over a 1-year follow-up period after trabeculectomy. Early VF improvement is more likely to occur in patients with mild/moderate glaucoma, whereas those with severe glaucoma show greater decline over one year. Our findings indicate that progression is observable using OCT, even in late-stage glaucoma.
Publisher: Wiley
Date: 2006
DOI: 10.1002/CNE.21225
Abstract: Ionotropic glutamate receptors have been associated with early development of the visual process by regulating cell differentiation, cell motility, and synaptic contacts. We determined the expression of functional ionotropic glutamate receptors during development of the mouse retina by assessing 1-amino-4-guanidobutane (agmatine AGB) immunolabelling after application of a range of glutamate analogs. Colocalization of AGB with calretinin and islet-1 allowed the identification of functional receptors in neurochemically defined neurons. Activation with kainate (KA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and N-methyl-D-aspartate (NMDA) resulted in AGB entry into neurons consistent with that found previous receptor subunit localization studies in the developing retina. Temporal analysis revealed that application of 50 microM KA activated receptors as early as embryonic day 18 in the ventricular zone and in the ganglion cell layer, whereas 30 muM AMPA activated cells predominantly in the ganglion cell layer. Cholinergic amacrine cells showed functional KA and AMPA receptors upon their insertion into the conventional amacrine cell layer from postnatal day 1 (P1). OFF cone bipolar cells showed functional KA receptors from P6, at a developmental age when they are known to make contact with ganglion cells. NMDA activation led to diffuse AGB labeling at birth among cells in the ganglion cell layer, whereas, at P1, regularly spaced cholinergic amacrine cells in the conventional amacrine cell layer started to be responsive to NMDA. Non-NMDA receptors were first to show functional activation in the developing retina, and cholinergic amacrine cells displayed functional ionotropic glutamate receptors after reaching their final destination.
Publisher: Wiley
Date: 25-03-2020
DOI: 10.1111/AOS.14419
Publisher: BMJ
Date: 22-05-2020
DOI: 10.1136/BJOPHTHALMOL-2019-314086
Abstract: To compensate the retinal nerve fibre layer (RNFL) thickness assessed by spectral-domain optical coherence tomography (SD-OCT) for anatomical confounders. The Singapore Epidemiology of Eye Diseases is a population-based study, where 2698 eyes (1076 Chinese, 704 Malays and 918 Indians) with high-quality SD-OCT images from in iduals without eye diseases were identified. Optic disc and macular cube scans were registered to determine the distance between fovea and optic disc centres (fovea distance) and their respective angle (fovea angle). Retinal vessels were segmented in the projection images and used to calculate the circumpapillary retinal vessel density profile. Compensated RNFL thickness was generated based on optic disc (ratio, orientation and area), fovea (distance and angle), retinal vessel density, refractive error and age. Linear regression models were used to investigate the effects of clinical factors on RNFL thickness. Retinal vessel density reduced significantly with increasing age (1487±214 µm in 40–49, 1458±208 µm in 50–59, 1429±223 µm in 60–69 and 1415±233 µm in ≥70). Compensation reduced the variability of RNFL thickness, where the effect was greatest for Chinese (10.9% p .001), followed by Malays (6.6% p=0.075) and then Indians (4.3% p=0.192). Compensation reduced the age-related RNFL decline by 55% in all participants (β=−3.32 µm vs β=−1.50 µm/10 years p .001). Nearly 62% of the in iduals who were initially classified as having abnormally thin RNFL (outside the 99% normal limits) were later reclassified as having normal RNFL. RNFL thickness compensated for anatomical parameters reduced the variability of measurements and may improve glaucoma detection, which needs to be confirmed in future studies.
Publisher: Springer Science and Business Media LLC
Date: 15-08-2018
DOI: 10.1038/S41598-018-30004-9
Abstract: We evaluated the prevalence of visual impairment (VI) and blindness among Chinese adults in the Singapore Chinese Eye Study (SCES, 2009–2011), and compared the trends with the Tanjong Pagar Survey, Singapore (TPS), conducted a decade earlier. The SCES comprised of 3,353 Chinese adults aged ≥40 years (response rate, 72.8%). Participants underwent standardized examinations, including measurements of presenting, and best-corrected visual acuity (VA). Bilateral VI (VA 20/40 to ≥20/200) and blindness (VA 20/200) were defined based on the United States definition (better-seeing eye). Age-standardized prevalence was calculated using the 2010 Singapore Chinese Population Census. Primary causes and factors associated with VI and blindness were evaluated. In SCES, the age-standardized prevalence of presenting bilateral VI and blindness were 17.7% and 0.6%, respectively the age-standardised prevalence of best-corrected bilateral VI and blindness were 3.4% and 0.2%, respectively. The previous TPS reported similar rates of best-corrected bilateral VI (3.8%) and blindness (0.3%). In SCES, cataract remains the main cause for both best-corrected bilateral VI (76.0%) and blindness (50.0%). Older age, female, lower income, lower educational level, and smaller housing type were associated with presenting bilateral VI or blindness (all P ≤ 0.025). These findings will be useful for the planning of eye care services and resource allocation.
Publisher: Elsevier BV
Date: 09-2020
Publisher: Springer Science and Business Media LLC
Date: 26-11-2019
DOI: 10.1038/S41598-019-54171-5
Abstract: Optical coherence tomography angiography (OCTA) is a well-established non-invasive retinal vascular imaging technique. It has been recently adapted to image the anterior segment and has shown good potential to image corneal vascularisation. The purpose of the study is to evaluate the usefulness of OCTA to monitor regression of corneal vessels following anti-VEGF (vascular endothelial growth factor) treatment using a previously established corneal vascularisation rabbit model. The regression of vessels following the treatment with aflibercept and ranibizumab anti-VEGFs using both topical instillation and sub-conjunctival injection was quantified using OCTA and compared with ICGA (indocyanine green angiography). Overall vessel density measurements using OCTA showed good correlation (r = 0.988, p 0.001) with ICGA, with no significant difference between the two treatment groups (p = 0.795). It was also shown that OCTA provided good repeatability outcomes of the quantitative measurements. Using Bland-Altman plots, vessel growth density values between anti-VEGF treatments were compared to control saline group. It was observed that aflibercept provided longer lasting effect than ranibizumab. We also observed that in both drugs, the topical route of administration topical provided longer regression outcomes compared to one-time sub-conjunctival injection. Thereby, with this pilot study, it was demonstrated that OCTA is a reliable imaging technique to follow-up and monitor corneal vascularisation and its treatment quantitatively.
Publisher: Springer Science and Business Media LLC
Date: 20-12-2017
DOI: 10.1038/S41598-017-18039-W
Abstract: We introduced a new method for detecting iris surface furrows and identify its associations with dynamic changes in iris volume in healthy eyes. Swept-source optical coherence tomography was performed on 65 subjects with open angle under light and dark conditions. Iris boundaries were identified and a reconstruction of the anterior iris surface was obtained. Furrows were detected by identifying locally deep (minima) points on the iris surface and reported as furrow length in millimetres. Iris volume was quantified. Associations between furrow length and dynamic changes in iris volume were assessed using linear regression model. With pupil dilation, furrow length increased (15.84 mm) whereas iris volume decreased (−1.19 ± 0.66 mm 3 ). Longer furrow length was associated with larger static iris volume, as well as smaller loss of iris volume with pupil dilation (β = −0.10, representing 0.1 mm 3 less loss in iris volume per 10 mm increase in iris furrow length P = 0.002, adjusted for age, gender and changes in pupil size). Our iris furrow length measurements are robust and intuitive. Eyes with longer furrows have larger iris volume and lose less volume during physiological pupil dilation. These findings highlight the potential for iris surface features as indicators of iris morphological behavior.
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.JTOS.2017.04.004
Abstract: To evaluate the incidence of symptomatic dry eye disease (SDED) and associated risk factors in a well-characterized cohort of ethnic Malays in Singapore. We included 1682 participants (mean age [SD]: 57 [10]years 55.4% female) without SDED from the Singapore Malay Eye Study (SiMES), a population-based longitudinal study with baseline examination (SiMES-1) conducted between 2004 and 2006, and follow-up examination (SiMES-2) conducted between 2010 and 2013. SDED was considered to be present if a participant answered "often" or "all the time" to any of the six questions from the Salisbury Eye Evaluation Study dry eye questionnaire. Age-standardized incidence of SDED was calculated as the crude 6-year cumulative incidence standardized to Singapore's population census. Gender-stratified multivariable log-binomial regression models were utilized to determine the independent risk factors of incident SDED. At the 6-year follow-up, 86 of 1682 participants had developed SDED, which was equivalent to an age-standardized 6-year incidence of 5.1% (95% CI 4.1-6.4%). There were no differences in the incidence of SDED between men and women (P = 0.9). Multivariable models revealed that presence of glaucoma and poorer self-rated health were independently associated with incident SDED in men (P = 0.003 and 0.03, respectively), while contact lens wear (P = 0.002), history of thyroid disease (P = 0.03), and having had cataract surgery (P = 0.02) were predictive of incident SDED in women. One in twenty adult Malays developed SDED over a 6-year period. Risk factors for incident SDED were different between men and women. Future studies and public health interventions should consider this gender-specific difference in risk factors.
Publisher: BMJ
Date: 04-10-2020
DOI: 10.1136/BJOPHTHALMOL-2019-314706
Abstract: To assess the agreement in measuring retinal nerve fibre layer (RNFL) thickness between spectral-domain (SD Cirrus HD, Carl Zeiss Meditec, USA) optical coherence tomography (OCT) and swept-source (SS Plex Elite 9000, Carl Zeiss Meditec) OCT using an OCT angiography (OCTA) scanning protocol. 57 participants (12 glaucomatous, 8 ocular hypertensive and 74 normal eyes) were scanned with two OCT instruments by a single experienced operator on the same day. Circumpapillary RNFL thicknesses were automatically segmented for SD-OCT and manually segmented for SS-OCTA scans. Agreement of global RNFL thickness, as well as average thickness in four quadrants was assessed using intraclass correlation coefficients (ICCs). There was excellent agreement in the inferior and superior quadrants and the global (all ICC .90), followed by good agreement in the temporal (ICC=0.79) and nasal (ICC=0.73) quadrants. The ICC values were similar in the subgroups except within the ocular hypertension group, where the nasal quadrant was less agreeable (ICC=0.31). SS-OCTA-derived RNFL thickness was on average 3 µm thicker than SD-OCT, particularly in the nasal (69.7±11.5 µm vs 66.3±9.3 µm p .001) and temporal (75.6±13.7 µm vs 67.9±12.3 µm p .001) quadrants. RNFL measurements taken with SS-OCTA have good-to-excellent agreement with SD-OCT, which suggests that the RNFL thickness can be sufficiently extracted from wide-field OCTA scans.
Publisher: American Medical Association (AMA)
Date: 12-2016
Publisher: Springer Science and Business Media LLC
Date: 10-02-2020
Publisher: Wiley
Date: 08-12-2022
DOI: 10.1111/AOS.15077
Abstract: To investigate the response of the superficial and deep capillary plexuses to hyperoxia and hypoxia using optical coherence tomography angiography (OCT-A) and retinal vessel analyzer. Twenty-four healthy volunteers participated in this randomized, double-masked, cross-over study. For each subject, two study days were scheduled: on one study day, hyperoxia was induced by breathing 100% oxygen whereas on the other study day, hypoxia was induced by breathing a mixture of 88% nitrogen and 12% oxygen. Perfusion density was calculated in the superficial vascular plexus (SVP) and the deep capillary plexus (DCP), using OCT-A before (normal breathing) and during breathing of the gas mixtures. Retinal vessel calibres in major retinal vessels were measured using a dynamic vessel analyzer. During 100% oxygen breathing, a significant decrease in DCP perfusion density from 41.7 ± 2.4 a.u to 35.6 ± 3.1 a.u. (p < 0.001) was observed, which was accompanied by a significant decrease in vessel diameters in major retinal arteries and veins (p < 0.001 each). No significant change in perfusion density in the SVP occurred (p = 0.33). In contrast, during hypoxia, perfusion density in the SVP significantly increased from 34.4 ± 3.0 a.u. to 37.1 ± 2.2 a.u. (p < 0.001), while it remained stable in the DCP (p = 0.25). A significant increase in retinal vessel diameters was found (p < 0.01). Systemic oxygen saturation correlated negatively with perfusion density in the SVP and the DCP and retinal vessel diameters (p < 0.005 each). Our results show that systemic hyperoxia induces a significant decrease in vessel density in the DCP, while hypoxia leads to increased vessel density limited to the SVP. These results indicate that the retinal circulation shows the ability to adapt its blood flow to metabolic changes with high local resolution dependent on the capillary plexus.
Publisher: American Medical Association (AMA)
Date: 03-2017
DOI: 10.1001/JAMAOPHTHALMOL.2016.5318
Abstract: There is limited understanding of the associations between systemic medication use and intraocular pressure (IOP) in the general population. To examine the association between systemic medication use and IOP in a multiethnic Asian population. In this post hoc analysis of the Singapore Epidemiology of Eye Diseases study, a population-based study of 10 033 participants (78.7% response rate) from 3 racial/ethnic groups (Chinese [recruited from February 9, 2009, through December 19, 2011], Malays [recruited from August 16, 2004, though July 10, 2006], and Indians [recruited from May 21, 2007, through December 29, 2009]), participants with glaucoma, previous ocular surgery, or trauma and an IOP asymmetry greater than 5 mm Hg between eyes were excluded. Intraocular pressure was measured using Goldmann applanation tonometry. An interviewer-administered questionnaire was conducted to collect data on medication and other variables. Data analysis was performed from August 1 through October 31, 2015. Associations between medication and IOP were assessed using linear regression models adjusted for age, sex, body mass index, ethnicity, and the medical condition for which the medication was taken (angiotensin-converting enzyme inhibitors [ACEIs], angiotensin receptor blockers [ARBs], and β-blockers adjusted for blood pressure, statins adjusted for lipids, and biguanides, sulfonylureas, α-glycosidase inhibitors [AGIs], and insulin adjusted for glycosylated hemoglobin). Medications associated with significant IOP differences were incorporated into regression models adjusted for concomitant use of multiple medications. Generalized estimating equation models were used to account for correlation between eyes. Of the 10 033 participants, we analyzed 8063 (mean [SD] age, 57.0 [9.6] years 4107 female [50.9%] 2680 Chinese [33.2%], 2757 Malay [34.2%], and 2626 Indian [32.6%] in iduals). Systemic β-blocker use was independently associated with an IOP of 0.45 mm Hg lower (95% CI, -0.65 to -0.25 mm Hg P < .001). Conversely, higher mean IOP was associated with use of ACEIs (0.33 mm Hg higher 95% CI, 0.08 to 0.57 mm Hg P = .008), ARBs (0.40 mm Hg higher 95% CI, 0.40-0.75 mm Hg P = .02), statins (0.21 mm Hg higher 95% CI, 0.02-0.4 mm Hg P = .03), and sulfonylureas (0.34 mm Hg higher 95% CI, 0.05-0.63 mm Hg P = .02). An interaction between medication classes for additive, synergistic, or antagonistic effects on IOP was not identified. Although systemic β-blocker use was associated with lower IOP and systemic ACEI, ARB, statin, and sulfonylurea use was associated with higher IOP in this study, the associations were modest at best. Only the associations with systemic hypoglycemic agents were greater than 1 mm Hg, a threshold that has translated to a 14% greater risk of incident glaucoma across 5 years in other studies. At this point, the effect of systemic medication on IOP in eyes with glaucoma is not well elucidated but important. Our findings indicate that patients with glaucoma may potentially be at risk of higher or lower IOP, depending on medication class, and this would in turn affect management of IOP control.
Publisher: Springer Science and Business Media LLC
Date: 13-08-2019
DOI: 10.1038/S41598-019-47770-9
Abstract: Retinal arterioles, venules and capillaries are differentially affected in diabetes, and studying vascular alterations may provide information on pathogenesis of diabetic retinopathy (DR). We conducted a cross-sectional study on 49 diabetic patients, who underwent fundus photography and optical coherence tomographic angiography (OCT-A). Fundus photographs were analysed using semi-automated software for arteriolar and venular parameters, including central retinal arteriolar equivalent (CRAE), central retinal venular equivalent (CRVE) and fractal dimension (FD). Capillary parameters were measured using OCT-A, including capillary density index (CDI) and capillary FD of superficial (SVP) and deep (DVP) vascular plexuses. Severe DR was defined as severe non-proliferative DR and proliferative DR. We found that eyes with severe DR had narrower CRAE and sparser SVP CDI than eyes without. In logistic regression analysis, capillary parameters were more associated with severe DR than arteriolar or venular parameters. However, combining arteriolar, venular and capillary parameters provided the strongest association with severe DR. In linear regression analysis, eyes with poorer visual acuity had lower CRAE and FD of arterioles, venules, and DVP capillaries. We concluded that the retinal microvasculature is globally affected in severe DR, reflecting widespread microvascular impairment in perfusion. Arteriolar, venular and capillary parameters provide complementary information in assessment of DR.
Publisher: Wiley
Date: 18-05-2020
DOI: 10.1111/AOS.14464
Publisher: Elsevier BV
Date: 09-2017
DOI: 10.1016/J.OPHTHA.2017.03.055
Abstract: To investigate the difference in corneal hysteresis (CH) and corneal resistance factor (CRF) between Indian and Chinese populations. Population-based cross-sectional study. Three hundred eighty-two Singaporean Indian persons and 764 Singaporean Chinese 50 years of age or older were included from the Singapore Indian Eye Study and Singapore Chinese Eye Study, respectively. Participants underwent standardized systemic and ocular examinations and interviewer-administered questionnaires for risk factor assessment. The CH and CRF were measured with the Ocular Response Analyzer (Reichert Ophthalmic Instruments, Buffalo, NY). Information on genetic ancestry was derived using principal component analysis. Linear regression models were used to investigate the association of CH and CRF with potential risk factors. Corneal hysteresis and CRF. After excluding participants with a history of intraocular surgery, a diagnosis of glaucoma suspect or glaucoma, refractive surgery, or presence of corneal abnormalities, CH and CRF readings were available for 382 Indian persons. For each Indian participant, 2 Chinese participants were selected and matched for age and gender (n = 764). There were no differences in the clinical measurements of CH (10.6±1.6 mmHg P = 0.670) or CRF (10.3±1.7 mmHg P = 0.103) between the ethnic groups. However, after adjusting for covariates, Indian persons had, on average, 0.18-mmHg higher CH levels than in Chinese (95% confidence interval [CI], 0.02-0.38 P = 0.031). Consistently, CH level was correlated significantly with genetic ancestry in the Southeast Asian population. Corneal resistance factor level was not associated independently with self-reported ethnicity (95% CI, -0.10 to 0.29 P = 0.335). Chinese have lower CH than Indian persons, and this disparity may reflect biomechanical differences of the cornea.
Publisher: Wiley
Date: 20-04-2021
DOI: 10.1111/AOS.14862
Abstract: We aimed to describe the global and localized correlations among visual field (VF) sensitivity, optic nerve head (ONH) perfusion measured by laser speckle flowgraphy (LSFG) and neural structure measured by optical coherence tomography (OCT) in open‐angle glaucoma (OAG) and to compare the floor effect for LSFG and OCT. Cross‐sectional, multicenter study including one eye each from fifty OAG patients (mean age 69.3 years average VF mean deviation, MD, −8.5 dB, range −25.17 to 0.85 dB) and fifty‐one controls. Patients underwent SITA standard 24‐2 automated perimetry and measurement of ONH perfusion, peripapillary retinal nerve fibre layer thickness (RNFLT) and macular ganglion cell‐inner plexiform layer thickness (GCIPLT). We tested the presence of a significant change (breakpoint) in the correlation slope with VF sensitivity to assess floor effect. The correlation between the LSFG parameter Mean All (MA) of the global disc area and MD ( r = 0.56, p 0.001) did not show a breakpoint, in contrast to the correlations between MD and OCT global parameters, which showed breakpoints at −8.53 and −4.05 dB for RNFLT and GCIPLT, respectively. Global and localized correlations with VF sensitivity were stronger for LSFG compared to OCT. In particular, LSFG outperformed OCT in the correlation with the central VF sector ( r = 0.50, p 0.001 and r = 0.06, p = 0.67 for MA and RNFLT, respectively). The global and sectoral correlations with VF sensitivity and the favourable floor effect compared to OCT indicate LSFG as a promising tool to monitor progression particularly in late‐stage glaucoma. Further longitudinal studies are warranted.
Publisher: BMJ
Date: 09-02-2022
DOI: 10.1136/BJOPHTHALMOL-2021-319739
Abstract: To use optical coherence tomography angiography (OCTA) parameters from both the retinal and choroidal microvasculature to detect the presence and severity of diabetic retinopathy (DR). This is a cross-sectional case–control study. OCTA parameters from retinal vasculature, fovea avascular zone (FAZ) and choriocapillaris were evaluated from 3×3 mm 2 fovea-centred scans. Areas under the receiver operating characteristic (ROC) curve were used to compare the discriminative power on the presence of diabetes mellitus (DM), the presence of DR and need for referral: group 1 (no DM vs DM no DR), group 2 (no DR vs any DR) and group 3 (non-proliferative DR (NPDR) vs proliferative DR (PDR)). 35 eyes from 27 participants with no DM and 132 eyes from 75 with DM were included. DR severity was classified into three groups: no DR group (62 eyes), NPDR (51 eyes), PDR (19 eyes). All retinal vascular parameters, FAZ parameters and choriocapillaris parameters were strongly altered with DR stages (p .01), except for the deep plexus FAZ area (p=0.619). Choriocapillaris parameters allowed to better discriminate between no DM versus DM no DR group compared with retinal parameters (areas under the ROC curve=0.954 vs 0.821, p=0.006). A classification model including retinal and choroidal microvasculature significantly improved the discrimination between DR and no DR compared with each parameter separately (p=0.029). Evaluating OCTA parameters from both the retinal and choroidal microvasculature in 3×3 mm scans improves the discrimination of DM and early DR.
Publisher: Wiley
Date: 06-04-2009
DOI: 10.1002/CNE.22029
Abstract: Retinitis pigmentosa reflects a family of diseases that result in retinal photoreceptor death and functional blindness. The natural course of retinal changes secondary to photoreceptor degeneration involves anatomical remodeling (cell process alterations and soma displacement) and neurochemical remodeling. Anatomical remodeling predominantly occurs late in the disease process and cannot explain the significant visual deficits that occur very early in the disease process. Neurochemical remodeling includes modified glutamate receptor disposition and altered responses secondary to functional activation of glutamate receptors. We investigated the neurochemical remodeling of retinal neurons in the rd/rd (rd1) mouse retina by tracking the functional activation of glutamate receptors with a cation probe, agmatine. We provide evidence that bipolar cells and amacrine cells undergo selective remodeling of glutamate receptors during the early phases of retinal degeneration. These early neurochemical changes in the rd/rd mouse retina include the expression of aberrant functional ionotropic glutamate receptors on the cone ON bipolar cells from postnatal day 15 (P15), poor functional activation of metabotropic glutamate receptors on both rod and cone ON bipolar cells throughout development/degeneration, and poor functional activation of N-methyl-D-aspartate receptors on amacrine cells from P15. Our results suggest that major neurochemical remodeling occurs prior to anatomical remodeling, and likely accounts for the early visual deficits in the rd/rd mouse retina.
Publisher: Wiley
Date: 04-2014
DOI: 10.1111/CEO.12331
Publisher: Wiley
Date: 12-12-2019
DOI: 10.1111/AOS.14327
Publisher: BMJ
Date: 04-01-2022
DOI: 10.1136/BJOPHTHALMOL-2020-317632
Abstract: To quantify retinal and choriocapillaris (CC) microvasculature in highly myopic (HM) eyes with myopic macular degeneration (MMD) using swept-source optical coherence tomography angiography (SS-OCTA). 162 HM eyes (spherical equivalent ≤ -6.0 dioptres or axial length (AL) ≥26.5 mm) from 98 participants were enrolled, including 60 eyes (37.0%) with tessellated fundus, 54 eyes (33.3%) with peripapillary diffuse chorioretinal atrophy (PDCA), 27 eyes (16.7%) with macular diffuse chorioretinal atrophy (MDCA) and 21 eyes (13.0%) with patchy or macular atrophy. PLEX Elite 9000 SS-OCTA was performed to obtain perfusion densities (PD) of the superficial and deep retinal capillary plexus, and CC signal voids (number, area and density). Retinal PD decreased with increasing severity of MMD. Multivariable analysis showed that after adjustment of age and other factors, retinal PD decreased significantly in eyes with longer AL (β≤-0.51, p<0.001) and with an MMD severity of MDCA or worse (β≤-1.63, p<0.001). Reduced retinal PD were significantly associated with worse vision (β≤-0.01, p≤0.04). In terms of CC signal voids, multivariable analysis showed that longer AL (p<0.001), but not MMD severity (p≥0.12) was significantly associated with CC signal void changes in the earliest stage of MMD. We demonstrate significant OCTA alterations in the retina and CC in HM eyes with varying severities of MMD. In eyes with early-stage PDCA, lower retinal PD and more extensive CC signal voids are predominantly associated with increasing AL. In contrast, in eyes with MDCA or worse, MMD itself was associated with sparser retinal and CC circulation.
Publisher: BMJ
Date: 04-10-2020
DOI: 10.1136/BJOPHTHALMOL-2019-314769
Abstract: To assess specific layers of the choroid in highly myopic young adults and to examine their associations with levels of myopia. We recruited 51 young myopes (n=91 eyes) from the Singapore Cohort of Risk Factors for Myopia cohort. We performed standardised optical coherence tomography (OCT) and OCT angiography imaging and developed a novel segmentation technique assessing choroidal layers’ thickness (overall choroidal thickness (CT), medium-vessel choroidal layer (MVCL) thickness, large-vessel choroidal layer (LVCL)) and vasculature (choroidal vessel density (%), choroidal branch area (CBA, %) and mean choroidal vessel width (MCVW, mm)). We found that eyes with extreme myopia (EM) had thinner vascular layers compared with high myopia (HM), that is, LVCL (36.0±1.5 vs 39.2±1.2 µm, p=0.002) and MVCL (185.5±5.7 vs 198.2±4.6 µm, p=0.014). Overall CT was thinnest in the nasal and inferior quadrants in EM (nasal: 157.1±9.6 vs 187.2±8.3 µm, p .001 superior: 236.6±11.1 vs 257.0±9.5 µm, p=0.02 temporal: 228.0±10.6 vs 254.3±8.8 µm, p=0.012 and inferior quadrant: 198.7±10.0 vs 239.8±8.3 µm, p= .001) when compared with HM. We also observed significantly more vessel branching in eyes with EM as compared with eyes with HM (CBA, 10.2%±0.7% vs 9.95%±0.8%, p=0.018). The novel segmentation technique and introduced choroidal parameters may serve as new biomarkers to study disease conditions in myopia.
Publisher: Public Library of Science (PLoS)
Date: 27-01-2017
Publisher: Wiley
Date: 29-06-2020
DOI: 10.1111/AOS.14527
Publisher: Wiley
Date: 21-12-2013
DOI: 10.1016/J.IJDEVNEU.2013.12.005
Abstract: This study characterizes the developmental patterns of seven key amino acids: glutamate, γ-amino-butyric acid (GABA), glycine, glutamine, aspartate, alanine and taurine in the mouse retina. We analyze amino acids in specific bipolar, amacrine and ganglion cell sub-populations (i.e. GABAergic vs. glycinergic amacrine cells) and anatomically distinct regions of photoreceptors and Müller cells (i.e. cell bodies vs. endfeet) by extracting data from previously described pattern recognition analysis. Pattern recognition statistically classifies all cells in the retina based on their neurochemical profile and surpasses the previous limitations of anatomical and morphological identification of cells in the immature retina. We found that the GABA and glycine cellular content reached adult-like levels in most neurons before glutamate. The metabolic amino acids glutamine, aspartate and alanine also reached maturity in most retinal cells before eye opening. When the overall amino acid profiles were considered for each cell group, ganglion cells and GABAergic amacrine cells matured first, followed by glycinergic amacrine cells and finally bipolar cells. Photoreceptor cell bodies reached adult-like amino acid profiles at P7 whilst Müller cells acquired typical amino acid profiles in their cell bodies at P7 and in their endfeet by P14. We further compared the amino acid profiles of the C57Bl/6J mouse with the transgenic X-inactivation mouse carrying the lacZ gene on the X chromosome and validated this animal model for the study of normal retinal development. This study provides valuable insight into normal retinal neurochemical maturation and metabolism and benchmark amino acid values for comparison with retinal disease, particularly those which occur during development.
Publisher: Elsevier BV
Date: 05-2017
DOI: 10.1016/J.DIABRES.2017.03.007
Abstract: The aim of this work was to determine the cumulative incidence and independent risk factors of prediabetes and type 2 diabetes (T2DM) in a well-characterized cohort of Malays in Singapore. We included 1137 participants (mean age [SD]: 55 (10) years 53.6% female) without diabetes (DM) at baseline from the Singapore Malay Eye Study, a population-based longitudinal study with baseline (2004-2006), and follow-up (2010-2013) examinations. Prediabetes was defined as an HbA1c between 5.7% and 6.4%, with no self-reported DM history or insulin/DM medication use. T2DM was defined as a random glucose level ≥200mg/dL or HbA1c>6.4% or use of insulin/DM medication. Age-standardized cumulative incidence was calculated as the crude 6-year cumulative incidence standardized to Singapore's Malay population census. Multivariable modified poisson regression models were utilized to determine the risk factors of incident prediabetes and T2DM. The age-standardized 6-year cumulative incidence was 11.2% (95% CI 9.5, 13.1%) for T2DM, and 20.4% (95% CI 16.4, 25.2%) for prediabetes. Hypertension, higher body mass index (BMI) and higher Hba1c levels were associated with increased risk of T2DM, while older age and higher high density lipoprotein (HDL) cholesterol were protective (all P<0.05). Only higher BMI and HbA1c levels were independently associated with incident prediabetes (all P≤0.001). While only one in ten adult Malays developed T2DM over 6-years, one in five developed prediabetes over the same time period. Our results suggest that evidence-based interventions addressing modifiable risk factors (obesity, prediabetes, hypertension, low HDL cholesterol) are needed to delay or prevent their onset.
Publisher: Wiley
Date: 09-2023
DOI: 10.1111/NYAS.15060
Publisher: Public Library of Science (PLoS)
Date: 28-04-2017
Publisher: BMJ
Date: 07-04-2022
DOI: 10.1136/BJOPHTHALMOL-2021-318907
Abstract: To examine the relationship between macular perfusion, as assessed using optical coherence tomography angiography (OCTA), and long-term visual outcome after surgical repair of macula-off rhegmatogenous retinal detachment (RRD). A prospective study of 29 patients who had undergone successful surgical repair of macula-off RRD. OCTA imaging was performed at month 3 and repeated at months 6 and 12 after surgery. Associations between OCTA parameters including, foveal avascular zone (FAZ) area, vessel density (VD) in the superficial capillary plexus (SCP) and deep capillary plexus (DCP), choriocapillaris flow deficit features and logMAR best-corrected visual acuity (VA) were assessed using a random intercept hybrid linear mixed model. Over the 1-year follow-up, VA improved (0.025 logMAR/ month, 95% CI 0.015 to 0.035) and FAZ area decreased (-0.020 mm OCTA measures of vascular perfusion in the macula may provide new pathophysiological insights and prognostic information related to macula-off RRD.
Publisher: Springer Science and Business Media LLC
Date: 09-04-2019
DOI: 10.1038/S41598-019-41917-4
Abstract: We investigated the characteristics of the choriocapillaris flow voids using optical coherence tomography angiography (OCTA) in 85 patients (164 eyes) with hypertension (mean ± SD age, 56 ± 11 years 45% women 20% poorly controlled BP 16% diabetes) who are without ocular diseases and determined possible correlations with systemic vascular risk factors. Data on 24-hour ambulatory blood pressure (BP), serum creatinine, and urine microalbumin/creatinine ratio (MCR) were collected. Estimated glomerular filtration rate (eGFR) was calculated based on CKD-EPI Creatinine Equation. OCTA imaging (6 × 6 mm scans AngioVue) with quantitative microvascular analysis of the choriocapillaris was performed. Linear regression was used to investigate the association of systemic risk factors with area (percentage), size (pixels) and number of choriocapillaris flow voids. Diabetes (β = 0.33 95% CI, 0.02 to 0.63) and daytime systolic BP (β = −0.13 95% CI, −0.24 to −0.02) were associated with areas of flow voids. Age (β = 0.21 95% CI, 0.06 to 0.36) and daytime diastolic BP (β = −0.18 95% CI, −0.34 to −0.02) were associated with size of flow voids. Age (β = −21.21 95% CI, −31.79 to −10.63) and nighttime diastolic BP (β = 13.89 95% CI, 0.61 to 27.17) were associated with number of flow voids. Kidney parameters were not associated with any features of flow voids. In patients with hypertension, a higher BP appeared to increase blood flow in the choriocapillaris which needs to be considered when using the OCTA to study eye diseases in hypertensives.
Publisher: BMJ
Date: 07-03-2017
DOI: 10.1136/BJOPHTHALMOL-2016-309842
Abstract: To determine the relationship between iris surface features and acute primary angle closure (APAC) in eyes with angle closure. Case-control study involving Asian patients diagnosed with previous APAC, primary angle closure suspect (PACS), primary angle closure (PAC) and primary angle closure glaucoma (PACG) at an eye centre in Singapore between August 2012 and January 2015. Participants underwent ophthalmic examination and digital slit-l iris photography. Iris surface features were graded based on crypts, furrows and colour. Fellow eyes of APAC were compared with PACS and PAC/PACG eyes with regard to their iris surface features. Occurrence of APAC. A total of 309 patients (71 APAC, 139 PACS, 47 PAC and 52 PACG) were included (mean age: 67.7±7.2 years and 36.6% male). Compared with PACS, higher crypt grade was significantly associated with lower odds of APAC (OR=0.58 for one grade higher in crypt grade p=0.027, adjusted for age, gender, ethnicity and pupil diameter). The results remained similar when compared with PAC/PACG group (OR=0.58 for one grade higher in crypt grade p=0.043). We did not observe any significant associations between iris furrows or colour with presence of APAC. Our study comprising Asian eyes with angle closure suggests that the presence of a higher crypt grading may be protective for APAC. As such, assessing iris surface architecture for crypts could be a new measure for risk stratification of developing APAC in eyes with angle closure.
Publisher: Springer Science and Business Media LLC
Date: 15-01-2018
DOI: 10.1038/S41598-017-18930-6
Abstract: In this cross-sectional study, we evaluated the association of dietary fish intake with varying severity of diabetic retinopathy (DR) and retinal vascular caliber in Asians with type 2 diabetes mellitus. 357 Asians (median age: 58 years 31% women 78% Chinese) were recruited from a tertiary eye care institution in Singapore. Fish consumption was evaluated using a validated food frequency questionnaire. Digital retinal photographs assessed for DR severity and retinal vascular caliber. Ordered logistic and linear regression models were used to investigate the association of fish intake with DR severity and vascular caliber. Increasing frequency of fish consumption was significantly associated with lower odds of having severe DR (odds ratio [OR] = 0.91, 95% CI: 0.84–0.99 per 1-unit increase of fish intake P = 0.038). Among those with no retinopathy, persons in quartile 4 fish intake had a wider retinal vascular caliber for arteriolar (β = 22.27 µm, 95% CI: 12.64–31.90 P-trend 0.001) and venular (β = 32.00 µm, 95% CI: 17.56–46.43 P-trend 0.001), than those in quartile 1 fish intake. Persons with higher fish intake had a decreased likelihood of having severe DR. In diabetics without retinopathy, higher fish intake was associated with wider retinal vascular caliber. Future research is needed to reinforce the direction of the casualty.
Publisher: Wiley
Date: 03-2016
DOI: 10.1111/CEO.12717
Publisher: Springer Science and Business Media LLC
Date: 30-12-2019
DOI: 10.1038/S41598-019-56996-6
Abstract: We characterized the age-related changes of the intra-retinal layers measured with spectral-domain optical coherence tomography (SD-OCT Cirrus high-definition OCT [Carl Zeiss Meditec]. The Singapore Epidemiology of Eye Diseases is a population-based, cross-sectional study of Chinese, Malays and Indians living in Singapore. Iowa Reference Algorithms (Iowa Institute for Biomedical Imaging) were used for intra-retinal layer segmentation and mean thickness of 10 intra-retinal layers rescaled with magnification correction using axial length value. Linear regression models were performed to investigate the association of retinal layers with risk factors. After excluding participants with history of diabetes or ocular diseases, high-quality macular SD-OCT images were available for 2,047 participants (44–89 years old). Most of the retinal layers decreased with age except for foveal retinal nerve fiber layer (RNFL) and the inner/outer segments of photoreceptors where they increased with age. Men generally had thicker retinal layers than women. Chinese have the thickest RNFL and retinal pigment epithelium amongst the ethnic groups. Axial length and refractive error remained correlated with retinal layers in spite of magnification correction. Our data show pronounced age-related changes in retinal morphology. Age, gender, ethnicity and axial length need be considered when establishing OCT imaging biomarkers for ocular or systemic disease.
No related grants have been discovered for Jacqueline Chua.