The characteristics of near prism induced fixation disparity curve in HongKong Chinese

The characteristics of prism induced fixation disparity curve at near were studied in 56 asymptomatic young adult Hong Kong Chinese (average age 21 ye ars). The percentage distribution of types of fixation disparity curves was found to be similar to some previous studies, with a higher prevalence of Type I curve (64.3%), followed by Type II (28.6%) and Type III (7.1%) curve s. No Type IV curve was revealed from the sample. Two modified measurement approaches were applied to study the effect of measurement techniques on th e parameters of fixation disparity curve obtained. A thorough description o f the techniques was given. Although a significant difference in the x- and y-intercepts was obtained between different methods, the curve type and sl ope were not affected. The average y-intercepts (fixation disparity) were 2 .72 min of are and 3.54 min of are from two methods respectively. Forty-one subjects had x-intercept (associated phoria) found from the curve. The ave rage values were 2.42 Delta base-out and 3.54 Delta base-out from two metho ds respectively. (C) 1999 The College of Optometrists. Published by Elsevie r Science Ltd. All rights reserved.