ORCID Profile
0000-0001-6919-5211
Current Organisations
UNSW Sydney
,
Singhealth
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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: American Medical Association (AMA)
Date: 12-12-2017
Publisher: Springer Science and Business Media LLC
Date: 12-06-2020
DOI: 10.1038/S41598-020-66736-W
Abstract: A major complication of hypertension is microvascular damage and capillary rarefaction is a known complication of hypertensive end-organ damage which confers a higher risk of systemic disease such as stroke and cardiovascular events. Our aim was to study the effect of hypertension on the retinal microvasculature using non-invasive optical coherence tomography angiography (OCTA). We performed a case-control study of 94 eyes of 94 participants with systemic hypertension and 46 normal control eyes from the Singapore Chinese Eye Study using a standardized protocol to collect data on past medical history of hypertension, including the number and type of hypertensive medications and assessed mean arterial pressure. Retinal vascular parameters were measured in all eyes using OCTA. In the multivariate analysis adjusting for confounders, compared to controls, eyes of hypertensive patients showed a decrease in the macular vessel density at the level of the superficial [OR 0.02 95% CI, 0 to 0.64 P 0.027] and deep venous plexuses [OR 0.03 95% CI, 0 to 0.41 P 0.009] and an increase in the deep foveal avascular zone. This shows that hypertension is associated with reduced retinal vessel density and an increased foveal avascular zone, especially in the deep venous plexus, as seen on OCTA and there is a potential role in using OCTA as a clinical tool to monitor hypertensive damage and identifying at risk patients
Publisher: BMJ
Date: 02-02-2019
DOI: 10.1136/BJOPHTHALMOL-2018-313282
Abstract: Diabetes is a major public health problem in migrants and ethnic minorities worldwide. We determined the incidence and risk factors of diabetic retinopathy (DR) in migrant Indians living in Singapore. We included data from 759 Indian adults with diabetes, who participated in the baseline (aged 40–80 years, 2007–2009) and 6-year follow-up 2012–2015 of the Singapore Indian Eye Study. Retinal photographs were graded for the presence and severity of DR using modified Airlie House Classification. Incidence was assessed in participants who were free of DR at baseline visit (n=501), while progression in those with DR but free of proliferative DR at baseline visit (n=189). Risk factors included demographic, lifestyle, socioeconomic, family history, genes, duration of diabetes, glycaemic control, insulin use, ocular and clinical factors. The 6-year age-standardised DR incidence and progression were 21.89% and 33.45%, respectively. HbA1c (risk ratio (RR) 1.41, 95% CI 1.28 to 1.55 per unit increase), current smoking (RR 1.63, 95% CI 1.02 to 2.62) and insulin use (RR 2.63, 95% CI 1.44 to 4.82) were associated with higher incidence, whereas estimated cerebrospinal fluid pressure (RR 0.90, 95% CI 0.82 to 0.98) and body mass index (BMI) (RR 0.74, 95% CI 0.60 to 0.93) were associated with lower incidence of DR. Higher HbA1c (RR 1.26, 95% CI 1.13 to 1.42), BMI (RR 1.26, 95% CI 1.02 to 1.56) and estimated cerebrospinal fluid pressure (RR 1.11, 95% CI 1.02 to 1.21) were associated with DR progression. The population attributable risk of HbA1c % was 41.29% and 49.63% for DR incidence and progression. DR incidence and progression in migrant Indians living in Singapore was more than double that reported in Indians living in urban India. Consistent with past studies, poor glycaemic control was an important predictor for incidence and progression of DR.
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.OPHTHA.2017.08.002
Abstract: To quantitatively determine how the reliability indices in standard automated perimetry (SAP) affect the global indices of visual field (VF) results in nonglaucomatous eyes. Observational, cross-sectional study. A total of 830 adults aged 40 to 80 years, without visual impairment, glaucoma, significant cataract, and major eye diseases, were selected from the population-based Singapore Chinese Eye Study (SCES). Study participants underwent a comprehensive and standardized ocular examination and VF assessment using a Humphrey Field Analyzer II (Carl Zeiss Meditec, Inc., Dublin, CA). The effects of the test reliability, as indicated by the false-negative (FN), false-positive (FP), and fixation loss (FL) rates, on global indices, as indicated by the mean deviation (MD) and pattern standard deviation (PSD), were analyzed with multivariable regression models. The MD and PSD. A total of 1828 VF results from 1235 normal eyes of 830 study subjects were included in the analyses. The multivariable regression analyses adjusted for age, gender, best-corrected visual acuity, and test duration showed that at lower frequencies of false answers (<15%), FNs decreased the MD (β [change in decibels {dB} per 5% increment in false answers] = -0.71 dB P < 0.001), whereas FPs increased the MD (β = 0.65 dB P < 0.001). At higher frequencies (≥15%), the false answers influenced the MD to a greater extent, where the β for the associations with FN and FP rates was -1.15 and 1.26 dB, respectively (both P < 0.001). We also found that when FN rate was <15%, higher FN rate increased the PSD (β = 0.51 dB P < 0.001), and the effect was slightly larger when FN rate was ≥15% (β = 0.71 dB P < 0.001). The effect of FPs on PSD was observed only when FP rate was <15% (β = -0.22 dB P < 0.001). The FL had no associations with the MD, and had minimal effects on the PSD. We quantified the effect of unreliable responses on the MD and PSD in SAP. Our study may allow clinicians to estimate how VF results are affected by varying degrees of unreliability, instead of relying on cutoff values for reliability indices.
Publisher: BMJ
Date: 20-05-2021
DOI: 10.1136/BJOPHTHALMOL-2020-315840
Abstract: To investigate the determinants of lamina cribrosa depth (LCD) in healthy eyes of Chinese and Indian Singaporean adults. The optic nerve head (ONH) of the right eye of 1396 subjects (628 Chinese and 768 Indian subjects) was imaged with optical coherence tomography (OCT, Spectralis, Heidelberg, Germany). LCD was defined as the distance from the Bruch’s membrane opening (LCD-BMO) or the peripapillary sclera (LCD-PPS) reference plane to the laminar surface. A linear regression model was used to evaluate the relationship between the LCD and its determinants. Both LCDs were significantly different between the two races (LCD-BMO: 421.95 (95% CI 365.32 to 491.79) µm in Chinese vs 430.39 (367.46–509.81) µm in Indians, p=0.021 and LCD-PPS: 353.34 (300.98–421.45) µm in Chinese vs 376.76 (313.39–459.78) µm in Indians, p .001). In the multivariable regression analysis, the LCD-PPS of the whole cohort was independently associated with females (β=−31.93, p .001), Indians subjects (β=21.39, p=0.004) (Chinese as the reference), axial length (Axl) (β=−6.68, p=0.032), retinal nerve fibre layer thickness (RNFL) (β=0.71, p=0.019), choroidal thickness (ChT) (β=0.41, p .001), vertical cup disc ratio (VCDR) (β=24.42, p .001) and disc size (β=−60.75, p=0.001). For every 1 year older in age, the LCD-PPS was deeper on average by 1.95 µm in Chinese subjects (p=0.01) but there was no association in Indians subjects (p=0.851). The LCD was influenced by age, gender, race, Axl, RNFL, ChT, VCDR and disc size. This normative LCD database may facilitate a more accurate assessment of ONH cupping using OCT in Asian populations.
Publisher: BMJ
Date: 10-08-2019
DOI: 10.1136/BJOPHTHALMOL-2018-312447
Abstract: To evaluate racial differences, and ocular and systemic determinants of macular thickness (MT), measured by spectral-domain optical coherence tomography (SD-OCT) in a normal multiethnic Asian population. MT was measured from a 6×6 mm 2 central macular area using the Cirrus high-definition OCT (HD-OCT) (Carl Zeiss Meditec, Dublin, CA). The associations between ocular and systemic factors with MT were evaluated using linear regression analyses with generalised estimating equation models to account for intereye correlation. 7447 healthy eyes (2577 Chinese, 2072 Malays and 2798 Indians) of 4510 subjects were included. Multivariable analysis showed that older age (per decade, β=−4.39), female gender (β=−5.74), diabetes (β=−1.10), chronic kidney disease (CKD) (β=−3.21), longer axial length (per mm, β=−2.34), flatter corneal curvature (per mm, β=−1.79) and presence of cataract (β=−0.94) were associated with thinner overall average MT (OMT) (all p≤0.026) higher total cholesterol (β=0.44 p=0.010) was associated with thicker OMT. All these factors were also associated with thinner central subfield MT (CSMT) (all p≤0.001), except for cataract, total cholesterol and CKD. Meanwhile, longer axial length (β=2.51 p .001) was associated with thicker CSMT. OMT (mean±SD) was thickest in Chinese (279.9±12.5 µm), followed by Malays (276.5±13.7 µm) and Indians (272.4±13.1 µm), with p≤0.003 for all interethnic comparisons. Similar trend was observed for CSMT. There are interethnic differences in MT profile among Asians, particularly between Chinese and Indians. Ocular and systemic factors affect MT measurements as well. This Asian-specific information may be incorporated into existing clinical interpretation of macular OCT scans to aid in improving the diagnostic and monitoring accuracy of macular diseases among Asians.
No related grants have been discovered for Quang Duc Nguyen.