The aim of the study was to investigate the Masking effect of the hydrogel lens and silicone hydrogel lens on the subjective with normal corneal shape and flat corneal shape after corneal refractive surgery, throughout refractive power and corneal topography map. Participants of 24 university students (means age:23.48±2.89years) consist of normal corneal shapes group(12) and flat corneal shapes after refractive surgery(LASIK-8, LASEK-4). The mean distance refractive error of Control groups(normal corneal shape) RE: -2.73D, Experimental groups(flat corneal shape) RE: -0.24. Inclusion criteria were on ocular pathology, able to wear soft contact lenses. The differences in the refractive power and corneal topography map between pre- and post-wearing the lenses were compared using 2 kinds of hydrogel contact lenses(-3.00D, 0.89Mpa, 0.49Mpa) and 2 kinds of silicone hydrogel contact lenses(-3.00D, 1.5Mpa, 0.8Mpa) in two groups. For the equipment of measurement, NVision-K5001(Shin nippon, Japan) was used to measure th refractive power and Keratograph 5M(Oculus, United state) was used to measure th corneal topography map.
As a result of this study, variations in the refractive power increased in the + direction in the Experimental group after wearing soft contact lenses. In terms of the corneal topography map was showed significant changes on the both groups after wearing soft contact lenses(p<0.05), but the refractive power and corneal topography map variations by lenses material were no significant difference pre- and post-wearing on the both groups. Therefore, wearing soft contact lenses show Masking effect. Especially the refractive power influence wearing soft contact lens on the flat corneal after corneal refractive surgery due to Masking effect. Therefore it should be cautious with prescription of soft contact lens for undergoing corneal refractive surgery.

Key words: Silicone hydrogel contact lens, Modulus, Corneal refractive surgery, Irregular astigmatism, Corneal topography