Abstract
Abstract: :
Purpose: To examine the relation of horizontal axial length, gender and anthropometric parameters in a random sample of Year 1 Sydney School children. Methods: The Sydney Myopia Study is currently surveying myopia and other eye conditions in a stratified random sample of around 1500 Year 1 students (aged 6 years) and 1500 Year 7 students (aged 12 years) from metropolitan schools in Sydney, Australia. The 6–year old examinations commenced in August 2003 and will be completed by May 2004. At November 2003, 394 Year 1 students had been surveyed, with data available for statistical analysis. Five repeated measures of axial length from each eye were taken using the Zeiss IOLMaster. Height and weight were measured, and body mass index calculated. Percentage body fat was measured utilising bioelectrical impedance analysis. Gender and anthropometric measurements of height, weight, body mass index and percentage body fat were assessed. Associations between axial length and these parameters were analysed in a multiple linear regression model. Results: Repeated axial length measures showed a high reliability with Pearson coefficients ranging from 0.92 to 0.99. As axial length in the two eyes was highly correlated, only the results from right eyes (N = 394) are reported. Axial length in boys (22.88±0.55mm) was significantly longer than in girls (22.43±0.72mm), p < 0.0001. After adjusting for exact age, axial length was statistically significantly associated with height both in boys and girls, p < 0.0001. For each centimetre increase in height, axial length increased by 0.025mm. The height related increase in axial length was greater in girls (0.029mm) than in boys (0.019mm) and statistically significantly related to weight in boys (ß = 0.016, p = 0.029) but not in girls (ß = 0.015, p = 0.14). No association between axial length and body mass index or body fat percentage was found. Conclusions: Measurement of axial length using IOLMaster is reliable. In the 6–year old age group, boys have longer mean axial length than girls. Axial length is linearly associated with height in both genders and is also associated with weight in boys but not in girls.
Keywords: clinical (human) or epidemiologic studies: prevalence/incidence • refractive error development • clinical (human) or epidemiologic studies: risk factor assessment