近视眼LASIK术后与RGPCL配戴后的点扩散函数对比分析

目的 通过测量点扩散函数（PSF）,对近视患者准分子激光原位角膜磨镶术（LASIK）后早期与硬性透气性角膜接触镜（RGPCL）矫正近视后明暗视下的视觉质量进行对比研究.方法 前瞻性病例对照研究.选择屈光度匹配的两组中高度近视患者进行对比观察.A组为LASIK组,22例（44眼）,等效球镜度为（-6.84±1.65）D,行常规LASIK；B组为RGPCL矫正组,25例（49眼）,等效球镜度为（-6.43±1.59）D,给予同一材料和设计的RGPCL矫正.术前及术后3个月,对两组行3 mm和6 mm瞳孔直径下的PSF检查.对两组矫正前后组内和组间的PSF差异分别采用配对t检验和协方差分析.结果 ①LASIK组：术后3个月,近视患者低中频率调制传递函数（MTF）值较术前下降（3 mm瞳孔直径,2.98～23.81 cpd;6 mm瞳孔直径,2.98～9.42 cpd;P均＜0.01）,而高频MTF值变化不明显.②RGPCL组：与戴框架眼镜时比较,3 mm瞳孔下,低中频率MTF值差异无统计学意义,而高频率MTF值升高（18.85～37.70 cpd,P均＜0.05）；6 mm瞳孔时,各空间频率（2.98～37.70 cpd）MTF值均有上升.③无论瞳孔大小,RGPCL组各空间频率MTF值变化均明显大于LASIK组（P均＜0.05）.结论 LASIK手术后早期患者视觉质量存在不同程度下降,而配戴RGPCL可改善患者视觉质量.

Comparison of point spread function in myopia treated by LASIK and RGPCL

Objective To measure and compare the visual quality in myopic patients corrected by laser in situ keratomileusis (LASIK) and rigid gas permeable contact lens (RGPCL) by using point spread function (PSF).Methods This was a prospective study.There were 2 groups of patients with middle-high myopia corrected using either LASIK or RGPCL:44 eyes of 22 patients received LASIK (group A),with the spherical equivalent (SE) (-6.84±1.65)D,while 49 eyes of 25 patients corrected by RGPCL (group B),with the SE(-6.43±1.59)D.The changes of the modulation transfer function (MTF) in their eyes were evaluated before and 3 months after LASIK in group A,before and after the fitting of RGPCL in group B by using the PSF examination under conditions of 3 mm and 6 mm pupil diameters respectively.The changes of PSF in each group before and after correction were compared and the differences between groups were statistically analyzed with paired samples t test and analysis of covariance.Results ① The MTF values at low-middle spatial frequencies were decreased 3 months after LASIK (3 nun pupil diameter,2.98～23.81 cpd; 6 mm pupil diameter,2.98～9.42 cpd,P＜0.01),which was a statistically significant decrease,whereas the changes of MTF at high frequencies were not significant.②Under the condition of 3 mm pupil diameter,the MTF values at high spatial frequencies were increased after fitting of RGPCL (18.85～37.70 cpd,P＜0.05),whereas at low-middle frequencies the difference was not significant.Under the condition of 6 mm pupil diameter,the MTF values were improved at all spatial frequencies after RGPCL (2.98～37.70 cpd,P＜0.05).③The changes of MTF values at all spatial frequencies in the RGPCL group were better than those in the LASIK group (P＜0.05).Conclusion LASIK can deteriorate the visual quality of myopic patients in the early stage after surgery,whereas RGPCL can improve it.The visual quality of myopic patients corrected by RGPCL is better than that of the early stage after LASIK.