[Comparative study of the effect of pilocarpine and tropicamide eye drops on corneal topography]

ABSTRACT

This study was conducted to evaluate the effect of contraction and relaxation of ciliary muscle caused by pilocarpine and tropicamide eye drops on corneal radius, central corneal power and corneal astigmatism. This prospective study was performed on sixty normal and healthy eyes of sixty volunteers with a mean age of 38.19 year [range 18 to 49 years] and without any ocular pathology. Volunteers divided into 2 groups of thirty, in the first group corneal topography of both eye were measured before and 30 minutes after instillation of topical tropicamide 0.5% in only one eye, and the other eye was the control eye and no drop was given. In the second group, the same routine was performed, except that subject received on drop of pilocarpine 1% in one eye. Statistical comparison between groups for the central corneal power, corneal radius and corneal astigmatism were performed using paired t test. In group 1, no significant changes were found in corneal radius, power and astigmatism, however, in group 2 subjects who have received pilocarpine eye drop, mean corneal radius value decreased significantly by 0.05 mm and mean corneal power increased by a plus power of + 0.32 D. There was no significant change in corneal astigmatism in both groups. It seems that pilocarpine induced ciliary muscle contraction which may cause pressure on corneal limbus of cornea and scleral spur that resulted in changes in corneal curvature. But tropicamide eye drop did not affect corneal radius and other corneal parameters and corneal topography can be carried out after instillation of tropicamide eye drop