[Effect of different medication time prior to corneal refractive surgery on tear film stability]

Objective: To investigate the effect of different medication time prior to corneal refractive surgery on tear film stability. Methods: Prospective cohort study. A total of 60 patients (60 eyes), including 38 males (63.3%) and 22 females (37.7%) with an average age of (24.2±5.1) years (form 18 to 37 years), who had planned for corneal refractive surgery with normal ocular surface disease index score were included in this study. The patients were divided into 1d group (medication of 1 day, 30 eyes) and 3d group (medication of 3 days, 30 eyes) randomly. The first tear break up time (FBUT), the average tear break up time (AVBUT) and the dry eye grade score were recorded on the examination day and the operation day with Keratograph 5M. The difference of FBUT and AVBUI between the two groups was compared with the independent sample t test. The difference of FBUT and AVBUT between the examination day and the operation day was compared with the paired t test. The difference of the dry eye classification between the two groups was compared using chi-square test. Results: The FBUT and AVBUT of 1d group and 3d group were (10.89±5.19)s and (10.88±6.82)s, (16.24±3.62)s and (16.21±4.74)s respectively in preoperative examination, and (10.65±6.03)s and (8.14±5.75)s, (15.14±5.30)s and (12.86±5.92)s respectively in operation day. There was no significant difference in FBUT and AVBUT between the two groups (t=0.01, 1,47, 0.02, 1.44; P>0.05). However, in the 3d group, the AVBUT of operation day decreased as compared with that of the examination day, and the difference was statistically significant (t=2.31, P<0.05). There was no significant difference in the distribution of dry eye classification between the two groups (χ(2)=0.07, 3.36; P>0.05). Conclusion: Both of medication of 1 day and medication of 3 days prior to corneal refractive surgery can provide a similar tear film stability, however more attention should be paid to the medication for patients with asymptomatic but abnormal BUT. (Chin J Ophthalmol, 2018, 54: 744-747).