Changes of Anterior Segment During Childhood: A Biometric Study

We reviewed data of biometric ocular components in 2006 survey of myopia conducted in Taiwan on prematurely born 108 schoolchildren to find the trend of ocular development and possible factors to change the ocular development in Taiwan. The refractive status was measured with an autorefractometer under cycloplegia. Lens thickness (LT), anterior chamber depth (ACD), and axial length (AL) were measured with biometric ultrasound. The results showed that AL of myopic group prominently increased with age from 7 years to 18 years. However, hyperopic and emmetropic eyes showed slight increase with age. The crystalline lens became thinner between the ages of 7 years and 11 years. Subsequent increases in the LT correlated with age and the stability of myopia. This phenomenon was found not only in myopic eyes but also in emmetropic and hyperopic eyes. The changes of ACD inversely correlated with changes of the lens. Among the school-age children, the ratio of lens/AL was found to be approximately 0.147 for emmetropes. However, the ratio was found to increase with age. The ratio of anterior segment (AS)/AL was found to be approximately 0.3 for emmetropic eyes among all age groups and less than 0.3 for the myopic eyes of schoolchildren. The refractive status of preterm children was probably decided by a complex combination among various components, usually with shorter ACD and thicker crystalline lens depending on how the ratio of each component matches. In addition, we found that the ratios of AS/AL (approximately 0.308), LT/AL (0.158), ACD/AL (0.151) were the possible ratios for the development of emmetropic eye in preterm children. During school age, the AL and ACD increased with the severity of myopia, in contrast, the LT decreased. After the age of 20 years, the ACD decreased with aging and the LT increased with aging. Lens thinning appeared to be compensatory in nature with respect to the increased AL of normal eye growth. Myopic excessive eye growth induces the lens to compensate by becoming much thinner. We found that the ratios of components of preterm children were not following the normal ocular growth, mainly because of the underdevelopment of the AS. The change of the ACD also inversely corresponded with the LT.