Abstract
Abstract: :
Purpose: Positional acuity is severely disrupted in amblyopia. Deficits in positional acuity may be used to identify amblyopia and monitor its response to treatment. Currently, most positional acuity tests are computer–based and cannot be easily incorporated into office routine. The purpose of this study is to validate a quick monocular positional acuity test using charts or flash–cards. Methods: 68 normal and 45 amblyopic children ages 3–15 yrs and 16 normal adults were tested using at least one of 3 test protocols (2AFC computer, 4AFC charts, or 2AFC flash–cards) based on the radial deformation stimulus initially described by Wilkinson et al (Vis Res 38:3555–68). Low–frequency large radial frequency patterns were utilized so that even severely amblyopic patients could be tested. Letter acuity was also measured. Results: Thresholds for the 3 protocols were not significantly different for normal adults (p=0.297) and for children (p=0.319). Chart test–retest differences were small and similar to interocular differences in normals (p=0.93). Interocular difference was not significant in normal adults (–0.04 logMAR computer, –0.04 logMAR charts, –0.04 logMAR flash–cards) or children (–0.14 logMAR computer, –0.01 logMAR charts, 0.14 logMAR flash–cards). Mean thresholds for amblyopic patients were significantly worse than for normals in all protocols (all p<0.005). The accuracy of discriminating the amblyopic patients from normals was similar for the computer and flash–cards (88% vs. 82%; z=0.82, ns). Accuracy of the charts was slightly poorer than the computer (74% vs. 88%; z=2.17, p<0.05) but similar to the flash–cards (74% vs. 82%; z=1.09, ns). Conclusions: The flash–card and chart protocols are simple and quick to administer allowing close interaction between the tester and subject. These test protocols are accurate and reliable for monocular testing in young children. Encouraged by these initial results we are exploring which radius and radial frequency maximizes sensitivity to amblyopia and adapting the 2AFC flash–card paradigm for FPL.
Keywords: amblyopia • visual development