Background After successful scleral buckle and cryotherapy for macular-off retinal detachment (RD),some patients have poor visual acuity without any clinically detected macular change,and the unsatisfactory postoperative visual acuity is difficult to explain.The purpose of this study was to determine the characteristics of subretinal fluid (SRF) after successful scleral buckle surgery for macula-off RD.Methods Twenty-eight eyes from 28 patients were included in this study.The patients underwent scleral buckle surgery combined with cryopexy for macular-off RD.After surgery,all eyes underwent thorough ophthalmologic examinations including slit-lamp biomicroscopy,best-corrected visual acuity (BCVA) test,and binocular indirect ophthalmoscopy.The BCVA prior to the operation,duration of RD,the duration of postoperative retinal reattachment,BCVA when SRF was observed,period required for the SRF to become undetectable,and the BCVA at the final follow-up were included in the clinical data for this study.Optical coherence tomography (OCT) and B-ultrasonography were used to confirm SRF,and fluorescein angiography (FFA) was carried out in several patients.BCVA when SRF was observed and BCVA at the final follow-up were evaluated using a paired ttest.Correlations between BCVA before the operation and duration of RD and BCVA at the final follow-up were analyzed using the Pearson correlation test.The type of SRF under OCT and BCVA at the final follow-up were compared using one-way analysis of variance (ANOVA).Results Postoperative retinal reattachment was achieved in 1.0-7.0 days (average,(2.7±2.1) days).After retinal reattachment,SRF was detected in all eyes by OCT 2 weeks postoperative,while B ultrasonography found no changes.The mean IogMAR BCVA was 0.35±0.27 at the time of the detection of SRF.The period for SRF to become undetectable ranged from 2.0 to 11.0 months (average,(6.3±2.3) months).The time of follow-up ranged from 24.0 to 36.0 months (average,(28.9±3.4) months).The mean logMAR BCVA improved to 0.30±0.23 at the final follow-up,which was significantly different from the mean IogMAR BCVA at the time of SRF detection (paired t-test,t=3.82,P ＜0.05).Postoperative OCT images were classified into three categories.FFA was carried out in 10 eyes and revealed no leakage or strain in the lesions.BCVA before the operation was significantly correlated with BCVA at the final follow-up (r=0.56,P ＜0.05).No significant correlation was observed between BCVA at the final follow-up and duration of RD (r=0.23,P=0.22).One-way analysis of variance (ANOVA) showed no significant difference between the type of SRF under OCT and BCVA at the final follow-up (F=0.21,P=0.81).Conclusions The presence of persistent SRF after successful scleral buckle surgery for macular-off rhegmatogenous RD may influence the BCVA or anatomic attachment.SRF was detected in all eyes by OCT at 2 weeks after the operation.Residual detachment persisted for almost a year after surgery in certain patients.Fluorescein angiography revealed no leakage or strain in the lesions.