Changes of the ocular anterior segment parameters before and after LASIK measured by Orbscan-II

Objective The ocular anterior segment parameters were measured before and after LASIK using Orbscan-Ⅱ to analyze possible errors in the parameters for different levels of myopia after LASIK.Methods The corneal thickness and anterior chamber depth for 88 eyes of 48 patients were measured with Orbscan-Ⅱ before LASIK and 1 month after.The patients were divided into 2 groups based on the severity of myopia before surgery:Group I:-2.00～-6.00 D;GroupⅡ:-6.25～-12.50 D.The theoretical post LASIK residual corneal thickness at the thinnest point and the actual corneal thickness measured after LASIK were compared,and the anterior chamber depth before and after LASIK was compared as well.Results In Group I,the difference between the theoretical residual corneal thickness and the thickness measured after LASIK was not statistically significant(P0.05);in GroupⅡ,this difference was statistically significant(P0.05).The thickness measured after LASIK was smaller than the theoretical residual corneal thickness.The difference between the central anterior chamber depth before and after LASIK was statistically significant in both groups(P0.05),and the central anterior chamber depth measured after LASIK was smaller than that before LASIK.Conclusion There were some errors in the measurement of corneal thickness and anterior chamber depth using Orbscan-Ⅱ after LASIK.Protrusion of the corneal posterior surface,edema,an unclean cornea after surgery,and an increase in accommodation are among the factors that may affect the measurements.