角膜瓣厚度对LASIK术后视觉质量的影响

Corneal flap thickness on visual quality after LASIK

目的探讨LASIK术中制作不同厚度的角膜瓣对术后视力、屈光度和对比敏感度等视觉质量指标的影响,为临床角膜瓣厚度的选择提供一定的理论依据。方法将接受LASIK术的患者140例(258眼)按照使用的Moria M2旋转式显微角膜刀刀头型号不同分为90组(使用90型刀头者)70眼、110组(使用110型刀头者)99眼和130组(使用130型刀头者)89眼,测量3组患者术前和术后3个月的裸眼视力、屈光度和位于1.5c·d-1、3.0c·d-1、6.0c·d-1、12.0c·d-1、18.0c·d-1空间频率上的对比敏感度,并进行比较。结果术后3个月,裸眼视力≥1.0者经标准化后在90组、110组和130组分别为92.64%、93.02%和94.96%,差异无统计学意义;3组柱镜度分别为(-0.41±0.26)D、(-0·40±0·25)D和(-0.42±0.24)D,差异无统计学意义;球镜度分别为(-0.89±0.68)D、(-0.69±0.85)D和(-0.39±0·67)D,等效球镜度(spherical equivalent,SE)分别为(-1.09±0·69)D、(-0.89±0.84)D和(-0.60±0.68)D,去除混杂因素影响后组间差异无统计学意义。术后近视性球镜度、SE随术前近视性球镜度、SE和切削深度增大而增大,随残留基质床厚度增大而减小。术后3个月5个空间频率上的对比敏感度3组间差异均无统计学意义。结论角膜瓣厚度不直接影响术后裸眼视力、球镜度、柱镜度、SE和对比敏感度。但制作薄角膜瓣保留更多基质床厚度,可间接降低术后近视性球镜度和SE,并减少术后角膜扩张和圆锥角膜等的发生,为激光切削留下更多空间。经验丰富的医师在保证安全的前提下,可根据具体情况和需要有选择性地制作薄角膜瓣。

Objective To investigate the effect of creating different corneal flap thickness on visual quality including visual acuity,refraction and contrast sensitivity（CS） after LASIK in order to provide theoretical basis for the choice of flap thickness in clinical practice. Methods A total of 140 patients （258 eyes） who underwent LASIK were divided into three groups according to models of Moria M2 rotated micro-keratome used in surgery, group 90 （with head 90 microkeratome,70 eyes）,group 110 （with head 110 microkeratome,99 eyes） and group 130 （with head 130 micro-keratome,89 eyes）, respectively. For each group, uncorrected visual acuity （UCVA）, spherical refraction, cylinder refraction and CS at 1.5c·d^-1、3.0c·d^-1、6.0c·d^-1、12.0c·d^-1、18.0c·d^-1 spatial frequencies were measured preoperatively and 3 months postoperatively. Results The postoperative standm dized rates of UCVA≥ 1.0 were 92.64% ,93.02% and %.96% in group 90,group 110 and group 130,respectively, which showed no significant difference. The postoperative cylinder refraction of three groups were （ -0.41 ±0.26）D,（ -0.40 ±0.25）D and（ -0.42 ±0.24） D, respectively, and no significant difference were found. The postoperative spherical refraction of three groups were（ -0.89 ±0.68 ）D, （ -0.69 ±0.85 ） D and（ - 0.39 ± 0.67 ） D; The postoperative spherical equivalent （SE） of three groups were （ - 1.09 ± 0.69 ） D, （ - 0.89 ± 0.84 ） D and （ - 0.60 ± 0.68 ） D, respectively, and no significant difference could be found when excluding the influence of confounding factors. Postoperative myopic spherical refraction and SE increased with the increasing of preoperative spherical refraction, SE and ablation depth, and the decreasing of residual stromal bed thickness. Postoperative CS at five spatial frequencies was not statistically significant in three groups. Conclusions Corneal flap thickness has no direct effect on postoperative UCVA, spherical refraction, cynlinder refraction, SE and CSF. However, creating thinner flaps can preserve more corneal stromal bed which indirectly resulted in a lower postoperative residual refraction, less incidence of keratectasia and keratoconus,and more space for laser ablation. On the premise of ensuring safety, experienced surgeons may choose to create relative thinner flaps based on the speciflc condition and requirement of patients.