Variations in ocular biometry in an adult Chinese population in Singapore:The Tanjong Pagar survey

PURPOSE. To describe the variation in ocular biometry in adult Chinese indi viduals in Singapore. METHODS. This study was a population-based, cross-sectional survey of adult Chinese persons aged 40 to 81 years residing in Tanjong Pagar district, Si ngapore. Axial ocular dimensions, including axial length (AL), anterior cha mber depth (ACD), lens thickness (LT), and vitreous chamber depth (VCD) wer e measured using an A-scan ultrasound device. Corneal curvature (CC) and no ncycloplegic refraction were measured with an autorefractor, with refractio n further refined subjectively. Lens nuclear opacity (NO) was graded clinic ally using the modified Lens Opacity Classification System III (LOCS III) s core. RESULTS. A total of 1717 subjects were eligible for the survey, of whom 123 2 (71.8%) participated. Biometric and refraction data were available for 10 04 (58.5%) phallic subjects. The AL, ACD, LT, VCD, CC, and LOGS III scores were 25.23 +/- 1.17 mm, 2.90 +/- 0.44 mm, 4.75 +/- 0.47 mm, 15.58 +/- 1.11 mm, 7.65 +/- 0.27 mm, and 3.2 +/- 0.9 (mean +/- SD), respectively. On avera ge, people aged 40 to 49 years, when compared with those 70 to 81 years, ha d longer ALs (mean difference, +0.58 mm), deeper ACDs (+0.52 mm), longer VC Ds (+0.72 mm), but thinner lenses (-0.70 mm) and less severe NO (-1.7 LOGS III score). CCs did not vary significantly with age. After controlling for age, women had shorter ALs and VCDs, shallower ACDs, but thicker lenses and steeper CCs than men. The variation in noncycloplegic refraction with age was nonlinear. Among people aged 40 to 59 years, a higher prevalence of hyp eropia was seen in older compared with younger persons (on average, a diffe rence of +1.3 D for every 10-year difference in age. P < 0.001), explained principally by shorter AL (and VCD) in older persons. Among those 60 to 81 years, this pattern was not obvious (a difference of -0.03 D for every 10-y ear difference in age, P = 0.12), as NO became an additional determinant of refraction, with greater degrees of NO in older person's driving refractio n in the "minus" direction. CONCLUSIONS. Ocular dimensions vary with age and gender in adult Chinese pe rsons in Singapore. The variation in noncycloplegic refraction in people 40 years and order may be explained by differences in axial lengths (principa lly vitreous chamber depths) between older and younger persons and, from 60 years onwards, differences in lens nuclear opacification as well.