Study of the effects of changes in ocular dominance in myopia patients after laser in situ keratomileusis

Objective To investigate the distribution of ocular dominance in myopic patients before and after laser in situ keratomileusis (LASIK) surgery, and the effects of the change in ocular dominance. Methods A prospective study was performed on 190 myopic patients (380 eyes) who received LASIK treatment. The dominant eye was identified with the hole-in-the-card test. Before operation, the patients were divided into 3 groups based on anisometropia and ocular dominance.Group A, 154 cases, the spherical equivalent difference was less than 1.75 D between the two eyes;group B, 19 cases, the spherical equivalent difference was 1.75 D or more between the two eyes and the dominance eye with higher diopter; group C 17 cases, the spherical equivalent difference was 1.75 D or more between the two eyes and the dominance eye with lower diopter. Refraction, ocular dominance and visual acuity were evaluated in all patients preoperatively and 1 month postoperatively.As part of the investigation, patients answered questionnaires after the operation. Chi-square test was used to compare the rate of dominance change, independent samples t test was used to compare the difference of measurement data. Results Before LASIK, 125 patients (65.8%) had right-eye dominance and 65 patients (34.2%) had left-eye dominance. After the operation, 92 patients (48.4%)had right-eye dominance and 98 patients (51.6%) had left-eye dominance, with 59 patients (31.1%)changing dominance. In group B, there was a higher rate of change in ocular dominance in eyes with greater anisometropia (47%)compared to groups A (29%) and C (29%) (x2=5.38, P＜0.05).Before operation, the equivalent spherical between dominant eye and the other was without any significant difference. After the operation, the dominant eyes' refractive error was (-0.29±0.89)D,lower than the preoperative dominant eyes (-0.42±0.91)D (t=2.448, P=0.015). The questionnaires did not show any statistically significant differences between dominance change group and no change group. Conclusion This study shows there is a change in ocular dominance after LASIK surgery,especially in those the dominance eye with higher diopter before operation. But the change has few effects on euphoropsia. Therefore, ocular dominance has plasticity after the critical period. The nondominant eyes have a greater degree of myopia than dominant eyes in subjects who had the operation. Key words: Keratonileusis,laser in situ;  Dominant eye;  Ocular dominance column; Plasticity