调制传递函数和对比敏感度函数评价LASIK术后早期视觉质量的研究

Early visual quality evaluation study after LASIK through modulation transfer function and contrast sensitivity function

目的:应用调制传递函数(modulation transfer function,MTF)检查和对比敏感度函数(contrast sensitivity function,CSF)检查评价近视患者准分子激光原位角膜磨镶术(Laser in situ keratomileusis,LASIK)术后视觉质量的变化。方法:前瞻性研究。47例92眼行LASIK手术的患者按照术前验光度数分为低度近视组(A组)、中度近视组(B组)、高度近视组(C组)。术前等效球镜值分别为-2.28±0.48D,-4.54±0.97D,-6.86±1.17D。分别于术前,术后1wk;1,3mo检查裸眼视力(the uncorrected visual acuity,UCVA)、最佳矫正视力(best-corrected visual acuity,BCVA)、屈光度、波前像差、3mm和5mm瞳孔下的MTF和昼视及夜视视远状态下的CSF。利用德国Zeiss公司WASCAAnalyer波阵面像差仪检查三组患者在3mm和5mm瞳孔下去掉高阶像差后的MTF曲线,将图像扫描并载入至Engauge Digitizer4.1数字化软件,得出一定空间频率下的MTF值;利用Optical6500对比敏感度测试灯箱(美国STEREO OPTICAL公司)测量患者在昼视及夜视视远状态下的CSF值。对数据进行配对t检验。结果:(1)术后1wk,CSF值与术前相比有明显下降。术后3mo,只有明环境下低空间频率和暗环境下低中度近视组的低空间频率的CSF值可以恢复至术前。近视度数越高,中高空间频率的CSF值越不容易恢复至术前。(2)3mm瞳孔条件下低度近视组100L/mm,150L/mm,300L/mm空间频率的子午曲线和中度近视组50L/mm空间频率的子午曲线的MTF值,在术后7d与术前相比已经无统计学差异。3mm瞳孔条件下中度近视组150L/mm,200L/mm,300L/mm空间频率的弧矢曲线、高度近视组250L/mm空间频率下的子午曲线的MTF值和5mm瞳孔条件下低度近视组100L/mm,300L/mm,400L/mm空间频率下的子午曲线、中度近视组400L/mm,500L/mm空间频率下的弧矢曲线,200L/mm,400L/mm空间频率下的子午曲线,高度近视组全部空间频率下的弧矢曲线,100L/mm,200L/mm,300L/mm空间频率下的子午曲线的MTF值术后3mo可恢复到术前水平。其余所有空间频率下的MTF值均能在术后1mo恢复至术前水平。结论:(1)MTF值比CSF值恢复更早,只有部分低空间频率的CSF值可以恢复至术前,而所有的MTF值均能恢复至术前水平。(2)MTF值在术后早期可以更早更全面和客观的反映出视觉质量的提高。(3)利用Carl Zeiss公司WASCA Analyer波阵面像差仪检测患者MTF可以更立体全面客观的反映术后人眼光学系统的改变。

AIM： To evaluate the changes of human eyes optical and visual quality after LASIK through modulation transfer function （MTF） measurement and contrast sensitivity function（CSF） measurement. METHODS： it was a prospective cohort study. Forty- seven patients （92 eyes） were divided into low myopia （-2.28±0.48D）, moderate myopia（-4.54±0.97D） and high myopia （ - 6. 86± 1. 17D） groups according to the spherical equivalent （SE） diopter before the surgery. The uncorrected visual acuity （ UCVA）, best- corrected visual acuity（BCVA）, SE diopter, wavefront aberration, CSF measurement, PSF measurement were examined before and after operation. The follow up visits of the patients were scheduled at the 7^th day, 1^st and 3^rd month. CSF curves, which were obtained with Carl Zeiss WASCA Analyzer wavefront aberration instrument under the 3.0mm and 5.0mm pupil size conditions, were scanned and loaded into Engauge Digitizer 4.1 digital software to obtain PSF data of certain space frequency. And CSF data were obtained with Optical 6500 of STEREO OPTICAL Company under day and night environment. The data were statistical analyzed with paired-t test. RESULTS： CSF data declined obviously compared with the preoperative data in early stage （7 days） after surgeries. Partial low space frequency CSF data （lowspace frequency CSF data in 3.0mm pupil size condition and moderate myopia patients＇ low space frequency CSF data in 5.0ram pupil size condition） recovered back to preoperative levels in 3 months after LASIK. The myopic degree was higher, the CSF values of moderate and high spatial frequency were harder to restore to preoperative levels. Most of the MTF values declined in 1 week after LASlK. MTF values approximately recovered back to preoperative levels in 1 month- 3 months after LASIK. Partial MTF values of 1 week after LASIK had no statistical differences compared to the preoperative data. CONCLUSION ： MTF values approximately recover back to preoperative levels earlier than CSF values. All the MTF values recover back to preoperative levels in 3 months after LASIK, but partial space frequency CSF values not. MTF values reflect the improvement of visual quality in early stage after LASIK. MTF data obtained with Carl Zeiss WASCA Analyzer wavefront aberration analyzer comprehensively and objectively reflect the optical system changes in early stage after LASIK.