Ava G Tan

Publications (12) View all

• Article: The Association between Ocular Biometry and Retinal Vascular Caliber is Comparable from Early Childhood to Adolescence.

  Bamini Gopinath, Jie Jin Wang, Annette Kifley, Ava G Tan, Tien Y Wong, Paul Mitchell
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  ABSTRACT: Purpose. We aimed to establish whether the change in retinal microvascular structure observed cross-sectionally with axial elongation and larger corneal curvature is comparable from early childhood to adolescence. Methods. 1,077 Sydney Paediatric Eye Study participants aged 36-<72 months and 1,740, 2,353, and 1,216 from Sydney Childhood Eye Study aged 6, 12 and 17 years, respectively, were examined. Quantifiable retinal vascular caliber measurements were obtained using validated computer-based methods. Ocular biometry measurements were performed according to standardized protocols. Results. After multivariable-adjustment, in children aged 36-<72 months, each 1.0-mm increase in axial length was associated with 3.67 and 6.53 μm narrowing of mean retinal arteriolar caliber (p=0.005) and venular caliber (p<0.0001), respectively. Each 1.0-mm increase in axial length in children aged 6, 12 and 17 years was associated with 5.30, 3.96 and 4.03 μm decrease in mean retinal arteriolar caliber, respectively. Each 1.0-mm increase in axial length in children aged 6, 12 and 17 years was associated with 7.12, 6.72 and 6.85 μm decrease in retinal venular caliber, respectively. Corneal curvature was inversely associated with retinal vascular caliber among all age-groups (p<0.001). Among those without significant refractive error (>0.00 and <2.00 D), significant inverse associations were observed between axial length and corneal curvature with retinal vessel caliber among all age groups. Conclusions. We demonstrate a similar magnitude of retinal vessel narrowing with axial length elongation and increasing corneal curvature from childhood through to adolescence. These data confirm the robustness of the associations between ocular biometric traits and retinal microvascular structural changes during childhood development.
  Investigative ophthalmology & visual science 01/2013; · 3.43 Impact Factor
• Article: Validity of a new computer-aided diagnosis imaging program to quantify nuclear cataract from slit-lamp photographs.

  Carol Yim-lui Cheung, Huiqi Li, Ecosse L Lamoureux, Paul Mitchell, Jie Jin Wang, Ava Grace Tan, Lily K Johari, Jiang Liu, Joo Hwee Lim, Tin Aung, Tien Yin Wong
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  ABSTRACT: To validate a new computer-aided diagnosis (CAD) imaging program for the assessment of nuclear lens opacity. Slit-lamp lens photographs from the Singapore Malay Eye Study (SiMES) were graded using both the CAD imaging program and manual assessment method by a trained grader using the Wisconsin Cataract Grading System. Cataract was separately assessed clinically during the study using Lens Opacities Classification System III (LOCS III). The repeatability of CAD and Wisconsin grading methods were assessed using 160 paired images. The agreement between the CAD and Wisconsin grading methods, and the correlations of CAD with Wisconsin and LOCS III were assessed using the SiMES sample (5547 eyes from 2951 subjects). In assessing the repeatability, the coefficient of variation (CoV) was 8.10% (95% confidence interval [CI], 7.21-8.99), and the intraclass correlation coefficient (ICC) was 0.96 (95% CI, 0.93-0.96) for the CAD method. There was high agreement between the CAD and Wisconsin methods, with a mean difference (CAD minus Wisconsin) of -0.02 (95% limit of agreement, -0.91 and 0.87) and an ICC of 0.81 (95% CI, 0.80-0.82). CAD parameters were also significantly correlated with LOCS III grading (all P < 0.001). This new CAD imaging program assesses nuclear lens opacity with results comparable to the manual grading using the Wisconsin System. This study shows that an automated, precise, and quantitative assessment of nuclear cataract is possible.
  Investigative ophthalmology & visual science 11/2010; 52(3):1314-9. · 3.43 Impact Factor
• Article: Smoking, socioeconomic factors, and age-related cataract: The Singapore Malay Eye study.

  Renyi Wu, Jie Jin Wang, Paul Mitchell, Ecosse L Lamoureux, Yingfeng Zheng, Elena Rochtchina, Ava G Tan, Tien Yin Wong
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  ABSTRACT: To describe the relationship of smoking, sex, and socioeconomic factors with age-related cataract in Malay adults in Singapore. In a population-based study, 3280 Malay individuals aged 40 to 80 years participated (78.7% response rate). All had interviews, systemic examination, and laboratory investigations. Lens opacity was graded from slitlamp and retroillumination photographs using the Wisconsin Cataract Grading System. Smoking-cataract associations were compared with the Blue Mountains Eye Study in Australia. Of 2927 participants (89.2%) with gradable lens photographs, 1338 (45.7%) had cataract. After adjusting for age, sex, body mass index, hypertension, and diabetes, current smokers had a higher prevalence of nuclear cataract (odds ratio [OR], 2.06; 95% confidence interval [CI], 1.46-2.98), cortical cataract (OR, 1.33; 95% CI, 1.02-1.74), posterior subcapsular cataract (OR, 1.39; 95% CI, 1.02-1.91), or any cataract (OR, 1.48; 95% CI, 1.10-1.99). These associations were not seen in the Blue Mountains Eye Study. Primary or lower education (OR, 1.67; 95% CI, 1.06-2.64) and low monthly income (OR, 1.43; 95% CI, 1.09-1.87) were both associated with nuclear cataract, while small-sized public housing was associated with posterior subcapsular cataract (OR, 1.70; 95% CI, 1.28-2.25). Among men, 43.5% currently smoked compared with only 3.2% of women. The population attributable risk of nuclear cataract due to smoking was estimated to be 17.6% in men. Smoking and indicators of low socioeconomic status were associated with cataract in Malay persons, with 1 in 6 nuclear cataract cases in men attributable to smoking. Smoking-cataract associations were stronger in Malay than in white persons.
  Archives of ophthalmology 08/2010; 128(8):1029-35. · 3.86 Impact Factor
• Article: The long-term relation among retinal arteriolar narrowing, blood pressure, and incident severe hypertension.

  Jie Jin Wang, Elena Rochtchina, Gerald Liew, Ava G Tan, Tien Yin Wong, Stephen R Leeder, Wayne Smith, Anoop Shankar, Paul Mitchell
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  ABSTRACT: The authors assessed associations between retinal vascular signs and incident severe hypertension in an older population-based cohort. At baseline (1992-1994), 3,654 residents aged 49-97 years living in the Blue Mountains area west of Sydney, Australia, were examined; respectively, 2,335 (75.1%) and 1,952 (76%) survivors were reexamined 5 and 10 years later. Retinal arteriolar and venular calibers were measured, and average central retinal artery and central retinal vein equivalents for that eye were estimated. Severe hypertension was defined by previous diagnosis of hypertension plus antihypertensive medication use or by systolic blood pressure > or =160 mmHg and/or diastolic blood pressure > or =100 mmHg at examinations. Of the 1,424 participants at risk, 618 developed severe hypertension over 10 years (cumulative incidence = 47.7%, 95% confidence interval: 44.9, 50.5). Participants who subsequently developed severe hypertension had significantly narrower mean central retinal artery equivalents than those who did not (187.0 vs. 191.9 mum, p < 0.0001). After adjusting for age, sex, body mass index, smoking, mean arterial blood pressure, and plasma glucose and triglyceride levels, baseline narrowing central retinal artery equivalent was associated with increased risk of severe hypertension (per standard deviation reduction, odds ratio = 1.1, 95% confidence interval: 1.1, 1.2; narrowest vs. widest quintile, odds ratio = 1.6, 95% confidence interval: 1.2, 2.1). These findings support structural narrowing in small arteries and arterioles antecedent to clinical onset of severe hypertension.
  American journal of epidemiology 07/2008; 168(1):80-8. · 5.59 Impact Factor
• Article: The LOC387715 polymorphism, inflammatory markers, smoking, and age-related macular degeneration. A population-based case-control study.

  Jie Jin Wang, Robert J Ross, Jingsheng Tuo, George Burlutsky, Ava G Tan, Chi-Chao Chan, Emmanuel J Favaloro, Andrew Williams, Paul Mitchell
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  ABSTRACT: To assess combined effects on the risk of age-related macular degeneration (AMD) by the LOC387715 polymorphism, smoking, and inflammatory or hemostatic factors. Population-based case-control study. Two hundred seventy-eight AMD cases (224 early, 54 late) and 557 controls matched for age, gender, and smoking, drawn from the Blue Mountains Eye Study cohort. Subjects were genotyped for the LOC387715 Ala69Ser polymorphism (rs# 10490924). Smoking was self-reported. Serum high-sensitivity C-reactive protein (CRP), interleukin 6 (IL-6), soluble intercellular adhesion molecule 1 (sICAM-1), fibrinogen, homocysteine, plasminogen activator inhibitor 1 (PAI-1), von Willebrand factor, and white cell count (WCC) were measured. Combined effects of this genetic variant plus any of these study factors on AMD risk were assessed using logistic regression models, adjusted for age and smoking. We defined interaction if the influence of 2 factors departed from the multiplicative scale, confirmed by a statistically significant interaction term. Otherwise, the combined effect was used. Age-related macular degeneration was graded using the Wisconsin grading system. Combined effects on the likelihood of early or late AMD were demonstrated for the LOC387715 Ala69Ser G/T and T/T genotypes with the markers high-sensitivity CRP (odds ratios [ORs], 1.2 for the highest tertile alone, 1.6 for G/T and T/T genotypes alone, and 2.2 for both G/T and T/T genotypes plus the highest tertile, compared with the G/G genotype with the 2 lower tertiles), IL-6 (corresponding ORs, 1.1, 1.6, and 2.2), sICAM-1 (ORs, 1.0, 1.5, and 2.3, respectively), and PAI-1 (ORs, 1.3, 1.7, and 2.3, respectively), but not with WCC, fibrinogen, homocysteine, and von Willebrand factor. Findings were similar for early and late AMD separately. Current smokers with G/T and T/T genotypes had strong combined effects on late AMD risk compared with those who never smoked or past smokers with the G/G genotype (ORs, 1.2 for current smokers alone, 1.8 for G/T and T/T genotypes alone, and 6.1 for current smokers plus G/T and T/T genotypes). We found no significant interaction but combined effects for the LOC387715 genotypes with 3 inflammatory markers and PAI-1 on the risk of early or late AMD, and with current smoking on the risk of late AMD.
  Ophthalmology 05/2008; 115(4):693-9. · 5.45 Impact Factor