Surgically Induced Astigmatic Change after Laser in Situ Keratomileusis using Manual Microkeratome

Lee, Jong Seok; Bae, Sun Ryang; Joo, Choun Ki

Abstract

We performed spherical LASIK operations using manual microkeratome and assessed the axis and magnitude of surgically induced astigmatism by vector analysis[Jaffe's rectangular coordinates]. Six month follow-up of 124eyes of 98 patients who were followed for 6 months or longer were included. Myopia ranged from -4.00 to -9.75 diopter. We divided eyes depending on the degree of myopia;group 1, 31 eyes between -4.00 and -5.75 diopter, group 2, 46 eyes between -6.00 and -7 .75 diopter, and group 3, 47 eyes between -8.00 and -9.75 diopter. Also, we compared the axis of surgically induced astigmatism between right eyes[73 eyes]and left eyes[48 eyes]. Preoperative astigmatic refraction was -0.63 +/-0.30 diopter in group 1, -0.67 +/-0.35 diopter in group 2, -0.67 +/-0.41 diopter in group 3.After 2 months, magnitude of surgically induced astigmatism was 0.84 +/-0.57 diopter in group 1, 1.08 +/-0.72 diopter in group 2, 1.19 +/-0.84 diopter in group 3[P=0.15], after 6 months, 1.01 +/-0.59 diopter in group 1, 1.16 +/-0.98 diopter in group 2, and 0.99 +/-0.59 diopter in group 3[P=0.52]. Change in the axis of vectorial-induced astigmatism was not statistically significant between right eyes and left eyes after 2 months[P=0.16], but significant after 6 months[p<0.05 ]. In conclusion, spherical LASIK using manual microkeratome may induce a significant change in magnitude of the astigmatism regardless the degree of myopia. The difference of astigmatic axis was statistically significant between right eyes and left eyes after 6 months. These changes and differences may require long-term follow-up and further investigation.