Abstract
COVID-19 is a disease first identified in Wuhan City, Hubei Province, China, in December 2019, causes by a SARS-COV-2 virus infection. By 27 October 2020, 43,921,473 confirmed cases were reported worldwide, with 1,166,389 COVID-19 deaths. Conjunctivitis has been reported in adults and pediatric patients with COVID-19.
Objective:
The aim of this meta-analysis is to estimate the odd Ratio (ORs) of conjunctivitis in patients with COVID-19.
Methods:
A systematic review and meta-analysis have been performed using the PubMed and Google Scholar literature search. The ORs of conjunctivitis in adults and pediatric patients is the outcome of this meta-analysis.
Results:
There have been 1041 articles published since the outbreak in December 2019, according to the latest literature. For the meta-analysis, 20 studies with a total of 3383 participants were included. The odds ratio (ORs) of conjunctivitis was 0.01 (95% confidence interval [CI]: 0.00–0.02). No bias has been reported.
Conclusion:
Conjunctivitis is the most common ocular manifestations reported in adults. This comprehensive meta-analysis quantifies the existing evidence linking conjunctivitis with COVID-19 and highlights the high percentage of heterogeneity that is shown in the current studies. Finally, it offers a single review article which includes all the current articles available for COVID-19 and conjunctivitis in adults and children.
Introduction
COVID-19 is a disease first identified in Wuhan City, Hubei Province, China, in December 2019, caused by a SARS-COV-2 virus infection. 1 In February, COVID-19 was formally announced by the World Health Organization (WHO) as COVID-19, formerly recognized as 2019 Novel Coronavirus (2019-nCOV) respiratory disease. The ambiguity of COVID-19 as it infects patients can vary from asymptomatic infection to serious illness and mortality. The case report of COVID-19 patients on a cruise’s ship (Diamond Princess ship) was one of the very early cases of a patient diagnosed with COVID-19 with viral conjunctivties. 2
SARS-COV and SAR-COV-2 have been explained to have identical findings linked to the same coronavirus family. In addition, it was emphasized that the infection is spread by the tears. 3 Although the likelihood of coronavirus spreading through tears appears small, it may survive in the conjunctiva, even in the absence of signs of conjunctivitis, suggesting the importance of using eye protection to avoid infection from external droplets and aerosols. 4 The key components considered to understand the “Ocular Pathway” are angiotensin-converting-enzyme-2 (ACE2) receptors and TMPRSS2 protein. 4 By 27 October 2020, 43,921,473 confirmed cases were reported worldwide, with 1,166,389 COVID-19 deaths. In adults and pediatric patients with COVID-19, conjunctivitis has been identified. The aim of this meta-analysis is to update eye care physicians of the ORs of conjunctivitis in COVID-19 patients as a review of the current evidence.
Methods
Trials identification and data consideration
The standards and guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) has been followed.5,6 PubMed search and other search engines “Google Scholar” have been used from December 2019 to 27 October 2020. The key words used were “COVID-19,” “Conjunctivitis” used individually or in combination. We selected randomized trials, observational studies, case series or case reports, and letters of research, letters to editors for confirmed cases of COVID-19 for the literature review, but only retrospective studies and observational studies for the meta-analysis. According to current scientific literature since the outbreak in December 2019 there have been 1041 papers written. The selected studies applied no language or other restrictions.
For bias detection, in each eligible study, a 7-point predefined quality control was used. The corresponding risk of bias was categorized as low (L), high (H), or unknown (U) to each quality item according to Higgins and colleagues5,7 Unknown is used to judge insufficient information. The Complete outcome data were judged as “Low risk” or “high risk” or “unknown.” The “low risk” is used when follow up percentage of participants lost was lower than 5% and “high risk” when follow up loss percentage was more than 20%.8,9 For other potential sources of bias, including the bias source, including the funding source reported in each protocol, the term “other bias” was used.5,10
The overall treatment effect was calculated and the study weight for each study was calculated. Due to the larger sample size of some of the studies, the study weight was calculated and the “true effect” for each study is shown. The larger sample size provides more information than a small sample size.
Data extraction
Inclusion criteria
(a) COVID-19 patients.
(b) Conjunctivitis was assessed, and the number of events was reported.
Exclusion criteria
a) If no data on ocular, manifestations neither conjunctivitis
b) Animal research
c) Case report, letter to the editorial or review
Quality of the comparative studies
Assessment of the quality characteristics used the following criteria: (1) random sequence generation (R), (2) allocation concealment (A), (3) blinding of participants and personnel (PB), 4) Blinding of outcome assessment (DB), (5) Incomplete outcome data (Attrition Bias) (AB), 6) Selective reporting (Reporting bias) (RB), and 7) Other bias (O). Each study was labeled with the right item either adequate (low risk of bias), unclear (unknown risk of bias), and inadequate (high risk of bias).
Literature screening and quality evaluation
One researcher independently screened the articles.
Statistical analyses
MedCalc 16.4.3 (Ostend, Belgium) software was used to statistically analyze the data and REV5. The ORs were calculated in each study. The study heterogeneity was assessed with the Cochran Q and I2 statistics. For the heterogeneity qualitative interpretation, I2 values of at least 50% were considered to reflect considerable heterogeneity, while values of at least 75% indicated large heterogeneity, as per the Cochrane Handbook. 5 Publication bias was evaluated using both graphical funnel plot 11 and Beggs statistical test. Random-effect model was used.
Results
Selection and characteristics of the study
PubMed and Google Scholar Searches of database resulted in 8681 articles; 1041 results were screened after duplicates removal. For the meta-analysis reviewer, 20 articles were analyzed with a total of 3383 participants. Eighteen articles were studied in adult patients with COVID-19 and two articles were studied in pediatric patients with COVID-19.12,13 The flow chart presenting the selection of eligible studies is summarized (Figures 1 and 2). The characteristics of the included studies are summarized (Table 1). Table 1 includes first author’s name, publication year, sample size, mean or median age or range of age reported and country of the study. Finally, the number of total COVID-19 patients and number of viral conjunctivitis patients (Table 1.)

Flow PRISMA chart presenting the total number of articles and the number of the included studies. Adapted from Moher and colleagues. 6

Forrest plot depicting pooled analysis.
Characteristics of included studies.
The age of the 3 conjunctivitis ages was listed, rather than the average of the 30 patients.
Not listed.
The ORs ranged from 0.00 to 5.17, which reveals the high heterogeneity between individual studies. The sample size also varied between 17 and 1099 COVID-19 patients (Figure 2).
Independent studies bias risk
The risk of bias of the included studies has been reviewed and studied by the author (Supplemental Table 1). Random sequence was low in 6 studies.12,14,19,20,22,27 Allocation concealment was low in five studies.12,14,20,22,27 The blinding participants and personnel (PB) is low in 10 articles.12,20–22,26–28,30–32 The blinding of outcome assessment (DB) is low in 12 articles.12,20–22,24–28,30–32
The incomplete outcome data (Attrition Bias) (AB) is low in 19 articles.12–18,20–22,24–32
Selective reporting (Reporting bias (RB) is 16 articles.12–14,16–18,20,21,24,26–32 All other bias is low in all 20 articles12–22,24–33 (Supplemental Table 1).
Overall final analyses
The systematic review of the selected 20 articles estimated the ORs of conjunctivitis of a total of 3383 COVD-19 patients. The ORs = 0.01; 95% confidence interval (CI): [0.00, 0.02] (Figure 2). Heterogeneity was statistically significant using the I2 value of 97% and p < 0.0001. In addition, no publication bias was detected using the funnel plot inspection.
Discussion
Conjunctivitis may be the first manifestation of the COVID-19 infection.15,23,34
Most patients in the 20 articles were hospitalized with COVID-19 (Table 2). Each article had at least two groups of patients, both non-severe and severe. Other articles were grouped into three classes, moderate, severe, and critical according to the PC-NCP guidelines 35 (Table 2).
Characteristics of COVID-19 patients that included in each study.
ICU, intensive care unit; NCP, Novel Coronavirus Pneumonia; RT-PCR, reverse transcriptase-polymerase chain reaction; SD, standard deviation; x, no data.
The majority of patients with viral conjunctivitis were male patients (Table 3). Other ocular manifestations have been documented, such as conjunctival hyperemia25,29,31 and secretion,25,30 conjunctival discharge,29,31 eye rubbing, subconjunctival bleeding, keratitis, and vitreous hemorrhages. Oruc and colleagues, recorded that 5% of COVID-19 patients had conjunctivitis and 5% had diplopia. 28 Acute conjunctivitis 21 and chronic conjunctivitis 22 were reported. Some studies reported conjunctivitis following the onset of COVID-19,13–20,22,24–27,29,30,32 while one study reported the diagnosis of conjunctivitis as the initial manifestation of COVID-19. 12 Guemes-Villahoz and colleagues 21 reported acute conjunctivitis in 13 patients prior to hospital admission, 12 patients between hospital admission and evaluation, and 10 patients at the time of evaluation. All of the included studies were hospitalized by COVID-19, except for one study included non-hospitalized patients. 31 All patients were laboratory-confirmed SARS-COV2.
Characteristics of conjunctivitis patients that included in each study.
B, bilateral; CC, conjunctival congestion; CR, critical; CS, conjunctival swab; DES, dry eye syndrome; ICU, intensive care unit; M, moderate; MD, mild; N, non-severe; NPS, nasopharyngeal swab; RT-PCR, reverse transcriptase-polymerase chain reaction; S, severe; U, unilateral.
One study confirms that conjunctivitis can be a symptom of COVID-19 infection related with more serious type of disease, which confirms previous study. 36
Furthermore, unilateral conjunctivitis in a 27-year-old COVID-19 male patient, has been reported as a first manifestation. 37 Only two patients with conjunctivitis had been reported in 72 laboratory-confirmed COVID-19 cases. 19 In addition, only one patient had conjunctivitis and foreign body sensation (2.3%) and tears in the 43 COVID-19 patients. 32 In contrast, other reports showed no ocular conjunctivitis which could be due to the very low sample size. 38
The prevalence rate of acute conjunctivitis in COVID-19 was reported ranging from 1.1 to 15.9.15,39 Other studies reported acute conjunctivitis in 31.6% of patients.23,39,40
One meta-analysis study showed that the probability of conjunctivitis in patients with non-severe COVID-19 was 4 out of 173, and severe COVID-19 was 5 of 926. 40 Wu et al. 15 showed that only one patient had the first symptoms of conjunctivitis.
There is certainly a difference in the percentage of conjunctivitis in COVID-19 patients that contributes to the aim of this meta-analysis. In our study, we found that 1% of COVID-19 patients are likely to have conjunctivitis with a total of 3383 COVID-patients.12–22,24–32
A related point to consider is that these findings have been reviewed retrospectively, and second, clinical symptoms have not been confirmed by clinical tests, but only have been subjectively reported by patients. In addition, because conjunctival mucosa can be a point of entry of COVID-19 infection due to overexpression of ACE2 receptors in epithelium from congested conjunctiva, 41 careful attention should also be given to protective measures such as the face shields and goggles.
This meta-analysis is consistent with the meta-analysis that showed that the incidence of ocular manifestations in COVID-19 patients ranged from 2% to 32%. 42 This meta-analysis review studied ORs of conjunctivitis and showed that the ORs ranged from 0.00 to 0.02.
The limitation of this study is (1) pediatric COVID-patients studies are needed, only 2 of the 20 studies in which the pediatric study was conducted, (2) only one reviewer performed the meta-analysis which may lead to bias, and (3) a greater sample size is needed.
Conclusion
Viral conjunctivitis is the most common ocular manifestations reported in adults. This comprehensive meta-analysis quantifies the existing evidence linking conjunctivitis with COVID-19 and highlights the high percentage of heterogeneity that is shown in the current studies. Viral conjunctivitis has been reported in males more than females. Finally, it offers a single review article which includes all the current articles available for COVID-19 and conjunctivitis.
Supplemental Material
sj-pdf-1-oed-10.1177_25158414211003368 – Supplemental material for COVID-19 and conjunctivitis: a meta-analysis
Supplemental material, sj-pdf-1-oed-10.1177_25158414211003368 for COVID-19 and conjunctivitis: a meta-analysis by Mashael Al-Namaeh in Therapeutic Advances in Ophthalmology
Footnotes
Author contributions
Conceived and designed the literature review: M.A. performed the article assessment, analyzed the data and wrote the paper.
Conflict of interest statement
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Ethical approval
This study was a review, and no ethical approval is required.
Supplemental material
Supplemental material for this article is available online.
References
Supplementary Material
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