Comparison between cycloplegic and noncycloplegic refraction in young adult myopes

SIGNIFICANCE: This study explores the difference between cycloplegic and noncycloplegic refraction in young adult myopes. PURPOSE: From the available literature, it is unclear whether cycloplegia is necessary when refracting young adults. This study investigates the agreement between noncycloplegic autorefraction and cycloplegic autorefraction and investigates factors affecting the agreement between the two methods. METHODS: In total, 125 myopes with ages ranging between 18 and 26 years were included from Australia and Vietnam. Each participant underwent noncycloplegic autorefraction and cycloplegic autorefraction. Cycloplegia was induced with 1% ophthalmic tropicamide. RESULTS: The mean spherical equivalent difference (95% confidence interval) between noncycloplegic autorefraction and cycloplegic autorefraction was -0.20 D (-0.25 to -0.14 D; t(124) = -7.18, p<0.0001). A mean difference of >0.25 D was seen in 46.8% of eyes. The lower and upper limits of agreement were -0.80 and 0.41 D, respectively. With univariate analysis, factors including age, degree of refractive error, accommodation amplitude, and distance phorias showed no impact on the average difference between cycloplegic autorefraction and noncycloplegic autorefraction. Yet, eyes with near exophoria (F-2,F-120 = 6.63, p=0.0019) and Caucasian eyes (F-3,F-121 = 2.85, p=0.040) exhibited the smallest paired differences. However, in the multivariate analysis, only near exophoria was associated with a lower mean difference. A significantly smaller proportion (34.9%) of eyes with near exophoria had a paired difference of -0.25 D or more compared with esophoria (50%) and orthophoria (65%; chi(2) = 6.6, p=0.038). CONCLUSIONS: Noncycloplegic autorefraction results in more myopic refractive error than cycloplegic autorefraction in young adults.