Retrospective Study
Copyright ©The Author(s) 2022. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Cases. Sep 26, 2022; 10(27): 9619-9627
Published online Sep 26, 2022. doi: 10.12998/wjcc.v10.i27.9619
Impact of COVID-19 pandemic on the ocular surface
Ana Marta, Joao Heitor Marques, Daniel Almeida, Diana José, Paulo Sousa, Irene Barbosa
Ana Marta, Joao Heitor Marques, Daniel Almeida, Diana José, Paulo Sousa, Irene Barbosa, Department of Ophthalmology, Centro Hospitalar Universitário do Porto, Porto 4099-001, Portugal
Author contributions: All the authors had full access to all the data and take full responsibility for the integrity of the data and the accuracy of the data analysis; Marta A, Marques JH, and Barbosa I were responsible for conceiving this research, gathering the data, presenting the results, and creating the manuscript; Barbosa I supervised this project and contributed with their expertise to its conclusion; and all authors read and approved the final manuscript.
Institutional review board statement: Approval was obtained from the “Departamento de Ensino, Formação e Investigação” (DEFI) (115-DEFI-118-CE).
Informed consent statement: Patients were not required to give informed consent to the study because it was waived by the institutional review board.
Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article.
Data sharing statement: Data used for analysis is anonymously available upon request.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Corresponding author: Ana Marta, Doctor, MD, MSc, Doctor, Department of Ophthalmology, Centro Hospitalar Universitário do Porto, Largo do Prof. Abel Salazar, Porto 4099-001, Portugal.
Received: December 17, 2021
Peer-review started: December 17, 2021
First decision: January 26, 2022
Revised: January 27, 2022
Accepted: August 21, 2022
Article in press: August 21, 2022
Published online: September 26, 2022

There have been increased reports of dry eyes in the coronavirus disease 2019 (COVID-19) pandemic era.


To analyze the differences in tear film properties from pre- and post-pandemic of the COVID-19 era.


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.


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).


Our study demonstrated that differences existed in tear film properties comparing data from the pre- and post-pandemic of the COVID-19 era.

Keywords: Ocular surface, Dry eye, Face masks, Mask-associated dry eye, COVID-19 pandemic

Core Tip: There were differences in tear film properties comparing the pre- and post-pandemic of the coronavirus disease 2019 era data. Over time, there was an increase in the lipid layer thickness, a decrease in the area of the meibomian glands, and a decrease in the blink rate. These changes seemed related to face masks and screen time. Therefore, the ophthalmologist must be aware of these changes and educate patients according to the most likely potential causal factor.