Objective To evaluate the effects of different spacing visual acuity (VA) charts on VA in curative amblyopic children as well as the effects of random-dot size and density on stereopsis using a stereopsis test system based on computer.
Methods This was a two-part study conducted in a referral practice. The subjects were 113 curative amblyopic children. (1) Single visual target, 1/4-time-, 1/2-time-, 1-time- and 2-time-spacing crowding VA charts were used respectively to examine the VA of each subject, and then the difference of VA among the five groups was analyzed. (2) A stereopsis test system based on computer was applied to examine stereopsis for 113 curative amblyopic children using random-dot stereogram (RDS) with four different sizes and three different densities of random-dots, respectively, and then the difference of stereopsis among the groups of different sizes and densities of random-dots.
Results (1) The average VAs of amblyopic children examined by single visual target, 1/4-time-, 1/2-time-, 1-time- and 2-time-spacing VA charts were (0.583±0.042), (0.412±0.033), (0.469±0.033), (0.523±0.041) and (0.562±0.039). Pairing comparison showed there were statistically significant differences among the five groups (P﹤0.05, except P between the single visual target group and the 2-timespacing group which was 0.079, the range of P value was 0.000~0.079 ). (2) There were no statistically significant differences among the different densities of random-dots when the size was constant (P﹥0.05, the range of P value was 0.102~0.879). Also there were no statistically significant differences among the different sizes of random-dots when the density was constant (P﹥0.10, the range of P value was 0.152~1.0).
Conclusions The crowding phenomenon still existed in curative amblyopic children. But the crowding phenomenon did not affect random-dot stereopsis test. It suggests that the mechanism of extracting RDS visual parallax information is different from the visual identification mechanism of fine visual targets. |
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