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Cause-and-Effect Association Not Established in RVO Incidence After COVID-19

Investigators noted selection bias and unaccounted-for confounders may make the increase in RVO incidence coincidental to COVID-19 infection.

Although there was an observed increase in the incidence of retinal vein occlusions (RVOs) following COVID-19 infection, a cause-and-effect relationship could not be established, according to new findings.

It was noted the time between diagnosis and increase in the condition may have been associated with delays in patients seeking care after visual changes or may indicate an extended prothrombotic state after infection.

“A cause-and-effect association could not be established in this retrospective, nonrandomized study because selection bias and unaccounted-for confounders may make the change in RVO incidence coincidental to COVID-19,” wrote study author Bobeck S. Modjtahedi, MD, Department of Research and Evaluation, Southern California Permanente Medical Group.

Although COVID-19 has been associated with systemic vascular damage, there is still limited data on the risk posed to the retinal vasculature.

The current retrospective cohort study analyzed patients enrolled in an integrated health care organization with a confirmed diagnosis of COVID-19 infection between January 2020 - May 2021.

Patients were excluded if they had a history of retinal artery occlusions (RAOs) or RVOs ≥6 months before their COVID-19 diagnosis or if they were enrolled in the organization for ≤6 months before diagnosis.

Within the study, the average biweekly incidence of new retinal vascular occlusions was compared between the pre-COVID-19 infection period (26 to 2 weeks before diagnosis) and the postinfection period (2 weeks before to 26 weeks after diagnosis).

The team calculated adjusted incidence rate ratios (IRRs) to compare the incidence of retinal vascular occlusions before and after COVID-19 diagnosis, after additionally accounting for baseline demographic characteristics, medical history, and hospitalization.

They included a total of 432,515 patients diagnosed with COVID-19 who met inclusion criteria, with a mean age of 40.9 years and 231,767 (53.6%) women.

Data show there were 12 RAOs (crude incidence rate, 3.00 per 1,000,000 patients) and 43 RVOs (crude incidence rate: 8.30 per 1,000,000 patients) in the 6 months before COVID-19 diagnosis.

Then, there were 16 RAOs (crude incidence rate: 3.00 per 1,000,000 patients) and 65 RVOs (crude incidence rate: 12.20 per 1,000,000 patients) in the 6 months after COVID-19 diagnosis.

The incidence of RAOs (adjusted IRR, 1.35; 95% CI, 0.64 - 2.85; P = .44) and RVOs (adjusted IRR, 1.54; 95% CI, 1.05 - 2.26; P = .03) increased in the 6 months after COVID-19 diagnosis.

The highest incidence rates of RAOs and RVOs were observed to have occurred 10 - 12 weeks and 6 - 8 weeks after COVID-19 diagnosis.

“The findings provide further evidence of the prothrombotic state induced by COVID-19 and indicate that the postinfection impacts may last several weeks,” concluded Modjtahedi. “Large epidemiologic studies are warranted to better define the association between retinal thromboembolic events and COVID-19 infection.”

The study, “Changes in the Incidence of Retinal Vascular Occlusions After COVID-19 Diagnosis,” was published in JAMA Ophthalmology.