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J. R. Drover, Y. Z. Wang, D. R. Stager, Sr., E. E. Birch; Validity of the Preschool Vernier Acuity Test. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4891.
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Detection of amblyopia and monitoring of treatment in preschoolers is difficult due to the cognitive demands (eg, optotype acuity) or lack of sensitivity (eg, grating acuity) of available tests. Although vernier acuity is sensitive to amblyopia, current methods of assessment are impractical for pediatric clinical use. We developed a new test of vernier acuity suitable for clinical assessment of young children. Here we examine its validity by assessing children with or recovered from amblyopia.
The Preschool Vernier Acuity Test consists of a 6-page booklet; each page contains 8 high contrast square-wave gratings. Half of the gratings possess a misalignment in stripe position that when detected, forms a second-order shape to be identified by the child. Each page contains two levels of misalignment which overall, ranges from 15 to 0.3 min in 0.17 log steps. Vernier acuity, grating acuity and optotype acuity were measured in the non-preferred eye of 17 amblyopic patients (age 7.3±3.3y) and the formerly non-preferred eye of 8 recovered patients successfully treated for amblyopia (age=6.4±2.9y). For comparison, 20 control children (age=6.7±1.9y) were also tested.
Amblyopic patients had poorer vernier acuity (0.41±0.37 logMAR) than control children (-0.15±0.21 logMAR; P < 0.00001). Recovered patients fell between these two groups (0.35±0.17 logMAR). Analysis of difference scores between grating acuity and vernier acuity indicated that relative to grating acuity, amblyopic patients demonstrated hypoacuity (-0.16±0.31 logMAR) whereas control children exhibited hyperacuity (0.14±0.18 logMAR, P<0.001). Once again, recovered patients fell between these two groups (-0.09±0.14 logMAR). Interestingly, across all children, vernier acuity was significantly correlated with optotype acuity (r=0.73, P<0.0000001).
The new test is easy to administer and reveals the selective loss of vernier acuity expected in amblyopic children. Furthermore, for all children, vernier acuity was a good predictor of optotype acuity. Collectively, these findings support the validity of the Preschool Vernier Acuity Test and suggest that it may represent a viable option for vision assessment in children too young for traditional optotype testing.
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