Ocular component characteristics of Chinese emmetropic children

Zhen-Yong Zhang^1,3*, Ren-Yuan Chu¹, Xing-Ru Zhang³, Xing-Tao Zhou¹, Matthew R. Hoffman² and  Jin-Hui Dai¹

¹Eye and ENT Hospital, Shanghai Medical College, Fudan University, Shanghai, China.

²University of Wisconsin-Madison, School of Medicine and Public Health, Department of Surgery, China.

³Putuo Hospital, Shanghai Chinese Traditional Medicine University, China.

*Corresponding author. E-mail: zzyly818@sina.com.

Accepted 10 April, 2009

   Abstract

Purpose to describe the ocular components of Chinese emmetropic children and determine if accommodation has long term effects on eye elongation. Autorefraction after cycloplegia was performed on 428 children (ages 3 - 14). 273 eyes met emmetropia the refractive error requirement for emmetropia (between +1.0 D and -0.5 D). Participants were divided into three groups: pre-school children (≤6 years old, group 1), grade school children (7 - 10 years old, group 2) and middle school children (>10 years old, group 3). Ocular components were measured using autorefraction and A-scan ultrasonography. When considering all subjects, there was a negative correlation between age and corneal power (r = -0.227, p = 0.0001), lens thickness (r = -0.263, p = 0.00001), and Gullstrand lens power (r = -0.452, p << 0.0001). There was a positive correlation between age and axial length (r = -0.432, p << 0.0001) and vitreous chamber depth (r = 0.505, p << 0.0001). Mean corneal power (p < 0.001) and lens power (p < 0.001) were significantly greater in pre-school children than in grade school children, while axial length (p < 0.001) and vitreous chamber depth (p < 0.001) were significantly greater in grade school children. Mean lens thickness (p = 0.01) and lens power (p = 0.07) were higher in grade school children than in middle school children, while axial length (p = 0.024) and vitreous chamber depth (p < 0.001) were higher in the middle school children. Ocular components may play different roles in emmetropization. In pre-school children, decreases in corneal power and lens power compensate for the increased axial length. In the grade school and middle-school children, decreases in lens power and lens thickness compensate for the change. Naturally occurring accommodation can also be caused by vision intensive schoolwork which could potentially lead to increased eye size.

Key words: Accommodation, eye elongation, ocular component, emmetropization.