Incidence Of Dry Eye Before Myopic LASIK And Effect Of Operative Parameters On The Incidence After Operation

Purpose To investigate the incidence of dry eye before myopic laser insitu keratomileusis(LASIK) and in the early stage after LASIK. To assessthe effect of myopic LASIK on the incidence of dryeye in patients withoutpreoperative dry eye, we compared preoperative tear function withpostoperative tear function. To determine the role of ablation depth ofcorneal stroma, flap thickness and width in developing dry eye.Methods A total of 198 eyes of 100 patients who wanted to undergoLASIK were screened randomly in this study and 139 eyes of 72 patientsunderwent the operation without preoperative dry eye. They were assignedto two groups according to flap thickness, ablation depth of corneal stroma,flap width and myopic diopters: Group A1, B1(flap thickness: 130μm,160μm), Group A2, B2(ablation depth range:＜90μm,＞90μm), Group A3,B3(flap width range:＜8.5mm,=8.5mm), Group A4, B4(myopic dioptersrange:＜6.00D,=6.00D). Subjective dry eye symptoms, fluoresceinstaining of the cornea, tear breakup time (BUT), Schirmer I test (SIT) andtear meniscus height (TMH) were evaluated before and at 1 week, 1 month after the operation. Data were evaluated by SPSS, version 13.0.Results We analysed above results of dry eye examination, the incidenceof dry eye was 25.3% in preoperative patients, but it was 40.29% at 1 weekand 33.8% at 1 month after LASIK in postoperative patients. The three mostcommonly symptoms of dry eye were dryness, foreign body sensation andvisual fatigue both before LASIK and after LASIK. Patients with dry eyesymptoms were statistically increased after LASIK (p＜0.05). Dry eyesymptoms were more severe in postoperative patients (p＜0.05).Fluorescein staining scores significantly increased at 1 week after LASIK.BUT,SIT,TMH values showed significantly decrease after operation. Thevalues of BUT, SIT and TMH were higher before operation, the incidenceof dry eye was lower after operation, and ablation deeper of corneal stroma,flap more thickness and more width had higher incidence of dry eye afteroperation. The multiple unconditional logistic regression analysis showedthe following factors had a propensity for higher risk of dry eye at 1 weekand 1 month after LASIK: the preoperative spherical equivalent of myopia(OR=1.309, p=0.012; OR=1.490, p=0.003), laser calculated ablation depth(OR=1.040, p=0.010; OR=1.057, p=0.005),and flap width (OR=7.850, p=0.014; OR=8.966, p=0.017).Conclusions The incidence of dry eye was 25.3% before myopic LASIK.If preoperative dry eye patients were not excluded, the incidence of dry eyemight add up to 54.55% at 1 week and 50% at 1 month, and was magnifiedafter LASIK. We found the incidence of dry eye after LASIK was inverselycorrelated with the preoperative values of BUT,SIT,TMH in patients without preoperative dry eye, but it was positively correlated with ablationdepth and flap width.