Evaluation of lipid layer tear film changes after femtosecond small incision lenticule extraction

BACKGROUND: Dry eye disease is common after refractive procedures due to tear film instability. There are several causative factors for tear film instability, but the state of individual components of the tear film is not assessed much in published literature. This article quantifies the lipid layer thickness (LLT) of the tear film using surface interferometry before and after the small incision lenticule extraction (SMILE) refractive procedure. OBJECTIVES: This study aimed to evaluate the effects of femtosecond SMILE on the postoperative stability of the LLT of the tear film. DESIGN: This was a prospective, interventional, non-case–control study. METHODS: A total of 160 eyes of 80 patients were enrolled in the study. The follow-up period was 6 months after surgery. A noninvasive surface interferometer was used to measure the thickness of the lipid layer before surgery and was repeated at 3 and 6 months after surgery. The main outcome measure was the change in average LLT at 3 and 6 months after SMILE and its statistical significance. RESULTS: There were 48 women and 32 men. Age ranged from 21 to 42 years (mean = 27 ± 6.4). Mean LLT at baseline was [oculus dextrus (OD) = 53.38 (±7.24) nm; oculus sinister (OS) = 52.21 (±6.95) nm], at 3 months [OD = 54.38 (±5.75) nm; OS = 53.26 (±5.70)], and at 6 months [OD = 53.31 (±5.66) nm; OS = 52.39 (±5.94)]. Mean LLT showed mild improvement at 3 months after surgery (OD = 53.38–54.38 mm, p = 0.0417; OS = 52.21–53.26 mm, p = 0.0398). There was no significant change in LLT from the baseline before surgery to levels 6 months after surgery (p = 0.8914 OD; p = 0.7368 OS). CONCLUSION: The SMILE refractive procedure did not alter the LLT that remained stable and adequate at 6 months postoperative follow-up.