Background. Diffuse lamellar keratitis is a rare yet severe postoperative complication that may arise following excimer laser correction of myopia. Research indicate that the incidence of this condition after LASIK ranges from 4.3 to 18.9 %, and after FemtoLASIK, it varies from 0.5 % to more than 37.5 %. Given the increasing popularity of LASIK and FemtoLASIK technologies, studying the frequency and clinical characteristics of this complication is crucial for enhancing treatment outcomes and patient safety. This study purposed to explore the clinical course and frequency of diffuse lamellar keratitis following different excimer laser technologies used for myopia correction. Materials and methods. We conducted a prospective, cohort, non-interventional study. It involved 180 patients (360 eyes) who underwent myopia correction using either LASIK (182 eyes) or FemtoLASIK (178 eyes). Postoperative monitoring included visual acuity, refraction, and biomicroscopy to identify potential complications, particularly diffuse lamellar keratitis. We examined the frequency and clinical course of the condition after each type of excimer laser correction. The observation period is 1 year. Results. Upon examination one week after excimer laser correction, the incidence of diffuse lamellar keratitis in the first group was 4.95 %, while in the second group it was 6.74 %. One month after surgery, there was a reduction in the frequency of diffuse lamellar keratitis: in the first group, it decreased to 3.30 %, and in the second group, to 2.81 %. By the three-month follow-up, the first group showed no manifestations of diffuse lamellar keratitis, whereas the second group had an incidence of 0.56 %. At the six-month follow-up, the incidence in the first group was 0.55 %, and there were no clinical manifestations of diffuse lamellar keratitis in the second group. At the one-year follow-up, neither group exhibited clinical signs of this disease. The clinical course and manifestations of diffuse lamellar keratitis did not differ between LASIK and FemtoLASIK throughout the study period. Additionally, it was found that 38.46 % of the patients had a history of SARS-CoV-2 infection. Conclusions. Our research revealed that the frequency of diffuse lamellar keratitis was 6.3 % after LASIK and 6.6 % after FemtoLASIK over a 1-year period. The clinical course and manifestations of the condition were similar for both LASIK and FemtoLASIK at all observation points. In was found that 38.46 % of patients who developed diffuse lamellar keratitis after excimer laser correction had a history of SARS-CoV-2 infection (from 2 weeks to 2 months). Future research should focus on investigating new local (ocular) and systemic (whole body) pathogenetic factors of diffuse lamellar keratitis following modern excimer laser methods for ametropia correction.
