Analyze Of Change And Effect Factors In Intraocular Pressure After Small Incision Lenticule Extraction

Objective:To evaluate the change and effect factors in intraocular pressure(IOP)measured by non-contact tonometer after small incision lenticule extraction(SMILE),and to calculate a regression equation for estimating IOP.Methods:In the prospective case-series study,87 patients(171 eyes)who underwent SMILE from April 2016 to April 2017 were enrolled.Preoperatively and 6 months postoperatively,IOP,diopter,central corneal thickness(CCT)and corneal curvature were measured.We not only analyzed the relationship between different variables and IOP postoperatively,but also calculated a correction formula for IOP measured by non-contact tonometer after SMILE.Results:IOP,corneal curvature,central corneal thickness all decreased postoperatively.Before and after SMILE,a t test showed that the difference of IOP,corneal curvature,central corneal thickness were significant(t=25.93?50.10?40.61?48.40?61.82,P<0.05).Postoperative IOP was positively correlated with preoperative IOP and postoperative CCT(r=0.608,0.237,P<0.01).Postoperative IOP was negatively correlated with preoperative spherical equivalent(SE),maximum lenticule thickness,the change of horizontal corneal curvature(?K1)?vertical corneal curvature(?K2)and average corneal curvature(?Km),and the change of central corneal thickness(?CCT)(r=-0.190?-0.170?-0.284?-0.191?-0.250?-0.201,P<0.05).No significant correlation were found neither between postoperative IOP and preoperatively CCT,K1,K2,Km,nor between postoperative IOP and postoperatively K1,K2,Km(r=0.117?-0.106?-0.061?-0.088?0.103?0.113?0.109,P>0.05).Themultiplelinearregressionequationis IOPpos=5.021+0.414×IOPpre-0.018×maximum lenticule thickness(F=57.78,P<0.001,R~2=0.400).Conclusions:Postoperative IOP measured by non-contact tonometer is underestimated after SMILE.The proposed correction formula may be used to predict postoperative IOP measurement.