To assay the effect of the cyclopentolate 1% on the cylinderic and spherical components of the refraction.

375 eyes of 195 subjects, including 74 males and 121 females, aged from 2 to 59 years were autorefracted before and 30 minutes after cyclopentolate 1% eyedrop instillation.

A statistically significant difference between the J0 vector [With The Rule (WTR) and Against The Rule (ATR) astigmatisms] values of the noncycloplegic and cycloplegic refraction was revealed (P= 0.006) while the J45 vector (oblique astigmatisms with axes at 45 and 135 degrees) values did not show statistically significant difference. Spherical Equivalent (SE) values in cycloplegic refraction were significantly more hyperopic than those yielded in dry refraction by mean difference of +1.16 ± 1.20 diopters (P<0.0001). Astigmatism difference was separately analyzed in emetropic, myopic and hyperopic eyes. Only in hyperopic eyes the J0 difference was significant (P=0.014)

Our findings indicated that cycloplegic drop can shift the WTR and ATR astigmatisms although the oblique astigmatisms remain uninfluenced. It seems that the accommodation process plays the most important role in the astigmatism changes. Further researches with larger sample sizes are needed to answer what mechanisms are involved in changing cylinder with cycloplegia.