Comparative evaluation of Asian and white ocular topography.

Abstract

To provide comparative ocular topography data from a substantial population of East Asian and white eyes. This study evaluated 675 subjects from three ethnic groups: white (n = 255), Chinese (n = 299), and Japanese (n = 121) at investigational sites in four locations: Wenzhou, China; Melbourne, Australia; Tokyo, Japan; and Jacksonville, USA. Subjects underwent the same measurements of ocular topography using identical equipment and protocols. A videokeratoscope (Medmont E300) was used to measure apical corneal radius, simulated K-reading (K), corneal shape factor (CSF), and corneal sagittal height at 10 mm in the two principal meridians. Digital photography was also used to measure ocular parameters including horizontal visible iris diameter (HVID), vertical palpebral aperture (PA), the intercanthal angle (ICA), and upper and lower lid angles. Mean HVID measurements were significantly smaller for the Chinese and Japanese groups than whites: 11.26, 11.10, and 11.75 mm, respectively. Horizontal K was significantly steeper for the white than the Chinese and Japanese groups: 7.79, 7.86, and 7.92 mm, respectively. The Chinese eyes showed significantly higher mean vertical CSF (i.e., more prolate) than the other two groups. The Chinese group had significantly narrower PA and steeper ICA than the other two groups: the mean PA and ICA values were 9.71, 10.31, and 10.58 mm and 7.56, 6.32, and 6.27 degrees, for the Chinese, Japanese, and white groups, respectively. One-third of the Chinese (32%) and 31% of the Japanese subjects showed no apparent supratarsal fold ("single eyelid"). There were also significant differences between groups for corneal sagittal height at 10 mm and upper and lower lid angles, but no significant differences for vertical K and horizontal CSF. This study has highlighted some differences in ocular topography between Chinese, Japanese, and white ethnic groups that may be relevant to soft contact lens fit.