The Effect Of Angle Kappa On High Order Aberrations After SMILE Surgery

ObjectiveTo investigate the effect of angle Kappa on high order aberrations before and after small incision lenticule extraction（SMILE）and whether it may affect visual quality after treatment decentration.To compare higher order aberrations（HOAs）after SMILE surgery in patients with and without intra-operative angle Kappa adjustments.Methods1.In this retrospective study,98 eyes of 98 patients undergoing SMILE surgery were selected.Only right eyes were investigated in the study.All patients underwent routine preoperative examinations and Pentacam topography.WaveScan aberrometer was used to measure the ocular high-order aberrations before surgery and at l month and 3 months postoperatively.The collected data were analyzed by the paired t test,repeated measures two-way analysis of variance and Pearson correlation.2.In this retrospective study,106 eyes of 106 patients who underwent SMILE surgery for correction of myopia and myopic astigmatism were divided into two groups:the first group consisted of eyes with intra-operative angle Kappa adjustment;the second group consisted of eyes without adjustment.Preoperative and postoperative visual outcome,refraction and HOAs measurements at 1 and 3 months were compared.Results1.At 6mm pupil diameter significant increases in total high order aberration（HOA）,coma,spherical aberration,and the 3rd,4th,5th,and 6th order aberration were observed postoperatively（all P<0.05）.2.There was a positive correlation between angle Kappa and total HOA,coma and the 3rd order aberration at each time point after surgery（total HOA:r=0.357,0.363;coma:r=0.310,0.341;the 3rd order aberration:r=0.343,0.371;all P<0.05）.3.The total HOA,coma,and the 3rd order aberration of the large angle Kappa group（0.26±0.05）mm and the small angle Kappa group（0.11±0.04）mm were compared.The difference was statistically significant(F_group=3.363,4.277,4.029,P<0.05).At 1 month and 3 months postoperatively,the total HOA,coma and the 3rd order aberration in the large angle Kappa group were significantly higher than those in the small angle Kappa group（P<0.05）.4.Overall comparisons were made between the angle Kappa-adjusted group and the non-adjusted group,and the difference in vertical coma was statistically significant(F_group=5.203,P<0.05).At 1 month and 3 months after surgery,the vertical coma of the angle Kappa-adjusted group was（0.153±0.107）μm and（0.157±0.094）μm,which was significantly lower than that of the non-adjusted group（0.204±0.117μm and 0.203±0.113μm,respectively）,and the difference was statistically significant（all P<0.05）.5.Subgroup analysis for eyes with large angle Kappa demonstrated that the vertical coma was significantly less in the angle Kappa-adjusted group at both 1 and 3months（all P<0.05）.6.No significant correlation was observed between angle Kappa and HOAs in angle Kappa-adjusted group.Conclusions1.Angle Kappa has a significant effect on the high order aberrations after SMILE surgery,suggesting that the presence of angle Kappa should be considered during surgery.2.Adjustment of angle kappa during SMILE resulted in less high order aberrations.It would provide more insight on how to optimize treatment centration in SMILE.