正视和近视青少年对比度视力与像差的关系

Association of visual performance and wavefront aberration in emmetropic and myopic teenagers

目的 比较初发性近视、进展性近视以及正视青少年明、暗环境下对比度视力（CVA）的差异,及其与像差和瞳孔的相关性.方法 横断面群组研究.58名年龄为12～16岁的青少年根据屈光状态及近视发生时间分为3组：正视组18人,等效球镜度（0.00±0.20）D;初发性近视21人,等效球镜度（-1.03±0.33）D;进展性近视19人,等效球镜度（-2.67±0.77）D.记录受试者左眼CVA、瞳孔直径和全眼波前像差.采用配对t检验、重复测量方差分析、单因素方差分析和Pearson相关分析对获得的数据进行处理.结果 初发性近视组的CVA低于进展性近视组和正视组（F=199.17、234.54,P＜0.01）,在低对比度（25％、10％）和暗环境下更为明显.3组青少年受试者明环境下全眼总像差（除去一阶和二阶离焦）、高阶像差、四阶球差以及彗差的均方根值[分别为（0.205±0.108）μm、（0.101±0.057）μm、（0.028±0.039）μm 以及（0.066±0.056）μm],低于暗环境下的各像差值[分别为（0.599±0.257）μm、（0.355±0.141）μm、（0.148±0.122）μm 以及（0.195±0.034）μm],差异具有统计意义（t=14.94、16.71、7.89、6.28,P＜0.05）.在同一亮度环境下,近视组像差与正视组之间差异无统计学意义.除明环境100％对比度下,CVA与总高阶像差存在负相关关系（r=-0.275,P＜0.05）外,其余情况下,CVA与高阶像差、瞳孔之间不存在相关性.结论 初发性近视者CVA低于进展性近视和正视者,差异在低对比度和暗环境下更明显.初发性近视CVA的下降与视网膜成像质量下降无直接关系,可能为皮层因素起主导作用.

Objective To investigate the differences in contrast visual acuity （CVA） under both bright and dark conditions in recent-onset myopic,progressive myopic and emmetropic teenagers; to investigate the correlation between CVA and wavefront aberration,together with pupil size; to study the possible mechanisms involved.Methods A cross-sectional trial design was used in this study.CVA was measured in 58 left eyes from 58 teenagers aged from 12 to 16 yeats.They were divided into 3 groups：emmetropes,18 subjects,with an average spherical equivalent refractive error （SER）of （0.00±0.20）D; recent onset myopes,21 subjects,with an average SER of （-1.03±0.33）D; and progressive myopes,19 subjects,with an average SER of （-2.67±0.77）D.All subjects underwent CVA testing with full spectacle correction under both bright and dark conditions with a Multi-Functional Visual Acuity Analyzer （MFVA-100）.Pupil size and monochromatic wavefront aberration were measured with a real-time image recording system and a Hartmann-Shack wavefront aberrometer.Data were analyzed using paired samples t test,repeated measure variance analysis,one-way ANOVA and Pearson correlation.Results Myopes had a lower CVA than emmetropes.And recent-onset myopes had a lower CVA than progressive myopes and emmetropes （F=199.17,234.54,P〈0.01）,especially under low contrasts （25%,10%） and dark conditions.Root mean square （RMS） values of total aberrations （C2-C7 without C20） and total higher-order aberrations （HOA）,spherical aberration and coma increased significantly with a pupil in dark light [（0.205±0.108）μm,（0.101±0.057）pm,（0.028±0.039）μm and （0.066±0.056）μm] than with a pupil in bright light [（0.599±0.257）μm,（0.355±0.141）μm,（0.148±0.122）μm and （0.195±0.034）μm） （t=14.94,16.71,7.89,6.28,P〈0.05）.There was no significant difference in the RMS values of HOA between emmetropes and myopes.Except for under bright and 100% contrast conditions,CVA had significant negative correlation with HOA,no correlation was found between aberration,pupil and CVA for all the groups under bright or dark conditions.Conclusion The CVA in recent-onset myopic teenagers was lower than both progressive myopic and emmetropic teenagers,especially under dark conditions and low contrasts.So far there is not enough evidence to show that the decrease in CVA in recent-onset myopes is related to pupil size and the deterioration of retinal image quality causcd by wavefront aberrations.We assume that cortical factors may play the major role in this phenomenon.