Analysis of changes in stray light and relevant factors before and after femtosecond laser in situ keratomileusis / 中华实验眼科杂志

ABSTRACT

Background As a newly developed refractive surgery,femtosecond laser in situ keratomileusis (LASIK) receives more and more attention.Changes in ocular stray light after femtosecond LASIK is an important problem that impacts visual quality.Some relevant research has been performed before,but the outcomes are conflicting.Objective This primary study was to investigate the change of stray light values before and after femtosecond LASIK and analyze the relevant factors underlying the change.Methods Clinical data from 109 eyes of 55 myopic patients who underwent femtosecond LASIK in Tianjin Eye Hospital from December,2010 through February,2011 were included in this study.Stray light values were measured and recorded by C-Quant stray light meter preoperatively,and 1 day,1 week,1 month and 6 months postoperatively.The stray light data were compared by repeated measures ANOVA,and the correlations among the stray light values with preoperative factors,such as age,equivalent sphere,pupil diameter and central corneal thickness(CCT),as well as with postoperative factors,such as residual bed thickness(RBT),RBT/CCT,ablation depth,ablation ratio,flap thickness,flap diameter flap base width and exiting energy,were analyzed statistically.Written informed consent was obtained from each individual at initial of this study.Results The stray light values were 0.90±0.19,1.10±0.19,1.02±0.18,0.96±0.16 and 0.94±0.15 pre-operation,and 1 day,1 week,1 month and 6 months after femtosecond LASIK.The stray light values increased significantly 1 day,1 week,and 1 month after surgery,showing significant differences among the various time points (F=17.699,P=0.000).The mean stray light value was higher in 1 week than that in 6 months after operation (t=2.412,P=0.017).No significant differences were found in the stray light values between 6 months and 1 month or pre-operation (t =0.779,P =0.437 ; t =-1.877,P =0.062).No significant correlations were seen between preoperative and postoperative stray light values with age,preoperative refractive diopter,pupil diameter or CCT (P＞0.05).The changes in stray light values 1 week,1 month and 6 months after surgery were negatively correlated with ablation depth(r=-0.226,-0.228,-0.241 ;P＜0.05) and ablation ratio(r =-0.149,-0.219,-0.255 ;P＜0.05).Conclusions Stray light values increase within 1 month and return to normal 6 months after femtosecond LASIK.Stray light values may be related to multiple setting laser parameters and factors during femtosecond LASIK.