Cycloplegic Effects on the Cylindrical Components of the Refraction.

It is important to predict which astigmatic patients require separate refraction for near vision. This study compared cylindrical components changes by cyclopentolate 1% for the low and high amount of astigmatism. The right eyes of 1014 healthy individuals (307 males and 707 females) with cylindrical refractive power more than -0.5 diopter on autorefractometer were selected. Both male and female patients in the age range of 17-45 years were refracted before and after cycloplegia, using 1% cyclopentolate. All volunteers were classified into 2 subgroups including the lower astigmatism group (-2.25 to -0.50) and the higher astigmatic group (-2.50 to over). Alpines' method was used to compare the effect of cycloplegic drop on cylindrical power. The mean age in the lower astigmatism group (29.58; 95% CI: 29.18 to 29.99 years) was not significantly different from the higher astigmatic group (29.85; 95% CI: 29.07 to 30.62) and there were no significant differences in gender between these two groups (P=0.54). Differences between wet and dry refraction in J0 (-0.03; 95% CI:-0.06 to -0.008) and J45 (-0.03; 95% CI:-0.06 to -0.01) were significant only in the higher astigmatic group. Axis changes by the cycloplegic drop in the lower astigmatism group were 3.51 (CI: 3.22 to 3.81) and axis changes by the cycloplegic drop in the higher astigmatism group were 2.21 (CI: 1.73 to 2.49). In patients with a lower amount of astigmatism (-2.25 to -0.50), additional near subjective refraction could be done for precise determination of axis and in patients with a higher amount of astigmatism (-2.50 to over), near subjective refraction might be done for precise determination of power.