Effect Of Pupil Size On Quality Of Vision At Night After SMILE Surgery

ObjectiveTo compare changes in visual quality at night before and after small incision lenticule extraction(SMILE)and evaluate the effect of pupil size on the night vision symptoms after SMILE surgery.To investigate other predictors for night vision symptoms before SMILE surgery.MethodsIn this prospective series case-observational study,49 right eyes of 49 patients undergoing SMILE surgery were included.Patients were divided into three groups according to preoperative mesopic pupil size measured by Colvard pupillometer:small pupil group(?5.5mm),medium pupil group(6.0–6.5mm),and large pupil group(?7.0mm).Forward scatter was measured by C-Quant straylight meter at baseline and at 1 week,1 month postoperatively,while questionnaires assessing quality of vision(night vision,glare,halo,starburst,hazy vision and blurred vision)were administered to patients.Preoperative and postoperative parameters were compared using repeated ANOVA.Parameters in three groups were compared by an one-way analysis of variance.Pearson correlation analysis were used to evaluate the correlation between pupil size and age,refractive error,straylight values and night vision symptom scores.The effect of other preoperative and postoperative variables including age,gender,refractive error and uncorrected visual acuity on questionnaire data were analyzed by a regression analysis.Results1.The mean pupil size was 6.60±0.68mm at 0.2 lux,and it was correlated with age negatively,however,no correlation was found between pupil diameter and spherical equivalent,spherical power or astigmatic power.2.There were no significant change in straylight values at 1 week and 1 month after SMILE compared to the preoperative parameters.There were no significant differences in straylight values among groups with different pupil diameters at baseline,1 week and 1 month after SMILE surgery by one-way ANOVA.3.Scores for glare,halos,starbursts,hazy vision and blurred vision at 1week and1 month postoperatively were significantly higher than those before surgery.There were no significant difference between scores at 1 week and 1 month after SMILE.4.There were no significant differences in night glare,halo and starburst scores among groups with different pupil diameters at baseline,1 week and 1 month after SMILE surgery by one-way ANOVA.Night glare,halo and starburst scores were not correlated with pupil diameter.5.Age was found to be the predictor for night glare at 1 week before SMILE(R~2=13.8%),and postoperative 1 month night glare predictors were age(r~2=26.5%)and preoperative spherical equivalent(r~2=6.6%).At 1 week after SMILE,patient reported night glare was positively correlated with age(r=0.382,P=0.007).While at 1month after SMILE,the frequency of night glare report increased with age(?'=0.672,P=0.000),and decreased with preoperative spherical equivalent(?'=-0.311,P=0.015)and scatter value(?'=-0.282,P=0.022).Most of theConclusions1.Mean scotopic pupil size in myopia eyes was 6.60±0.68mm,correlated with age negatively and not correlated with refractive error.2.Patient reported night vision symptoms increased after SMILE surgery,while straylight values didn't change significantly,suggesting that there was a decline of night visual quality at early period after SMILE.3.Pupil size had no significant effect on the straylight values,occurrence of glare,halos,starbursts and other vision problems such as hazy vision and blurred vision after SMILE.4.Age could be a factor related to short-term night glare,that is,older patients tend to report more night glare.5.Night glare reports could be predicted by preoperative spherical equivalence,and patients with higher refraction errors tend to experience more serious night glare.