Impact of COVID-19 pandemic on the ocular surface

BACKGROUND: There have been increased reports of dry eyes in the coronavirus disease 2019 (COVID-19) pandemic era. AIM: To analyze the differences in tear film properties from pre- and post-pandemic of the COVID-19 era. METHODS: It was a retrospective comparative study. Patients were divided into three groups according to the data of multimodal ocular surface evaluation: (1) Group 1 if it was before Portugal lockdown decision (from August 2019 to March 2020); (2) Group 2 if it was after Portugal lockdown decision but without mask mandate (from April 2020 to October 2020); and (3) Group 3 if it was after Portugal lockdown but with mask mandate in health public highway (from November 2020 to April 2021). The following variables were analyzed: Lipid layer thickness, blink rate, Schirmer test, tear meniscus height, tear osmolarity, non-invasive break-up time, and loss area of the meibomian glands. RESULTS: The study included 548 eyes of 274 patients, aged 18 years to 89 years, with a mean age of 66.15 ± 13.40 years at the time of multimodal ocular surface evaluation. Compared to group 1: (1) Mean lipid layer thickness was better in group 2 (P = 0.001) and group 3 (P < 0.001); (2) Schirmer test was similar in group 2 (P = 0.576) and better in group 3 (P = 0.002); (3) Tear osmolarity and loss area of the meibomian glands were worse in group 2 (P = 0.031 and P < 0.001, respectively) and in group 3 (both with P < 0.001); (4) Blink rate and tear meniscus height were similar in group 2 (P = 0.821 and P = 0.370, respectively) and worse in group 3 (P < 0.001 and P = 0.038, respectively); and (5) Non-invasive break-up time was worse in group 2 (P = 0.030) and similar in group 3 (P = 0.263). CONCLUSION: Our study demonstrated that differences existed in tear film properties comparing data from the pre- and post-pandemic of the COVID-19 era.