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.