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COVID-19 infection may be boosting the numbers of a rare ocular condition in which vision is threatened when veins in the retina are blocked, eye specialists in Southern California report.

Risk of retinal vein occlusion was higher in the 6 months after infection than in the 6 months prior (adjusted incidence rate ratio [IRR] 1.54, 95% CI 1.05-2.26, P=0.03), according to Bobeck Modjtahedi, MD, a vitreoretinal surgeon at Kaiser Permanente Southern California in Baldwin Park, California, and colleagues.

The number of cases reported was still very small, with crude rates of 8.3 cases per million patients in the 6 months before an infection and 12.2 per million in the 6 months after, and the link to COVID-19 isn't definitive, the group cautioned in .

However, "these results are compelling and fit in with the general trends we have seen in COVID-19 and systemic vascular disease," Modjtahedi told 番茄社区app. "Although retinal vein occlusion remains an uncommon event after COVID-19 infection, these events can result in irreversible vision loss."

Researchers have linked a long list of neuro-ophthalmic/retina conditions to COVID-19, including photophobia, retinal hemorrhage, and optic neuritis.

For the new study, Modjtahedi's group retrospectively tracked 432,515 patients in Kaiser Permanente Southern California's health system who tested positive for COVID-19 from January 2020 to May 2021 to examine changes in the incidence of retinal artery and vein occlusions following an infection.

According to Modjtahedi, retinal artery and vein occlusions occur when blockages disrupt blood flow either in or out of the eye.

"Patients can suffer vision loss, which is often permanent, although there are treatments for secondary associated events like macular edema," he said. "These conditions are often seen in patients who have systemic vascular diseases like diabetes and hypertension."

For retinal artery occlusions, the group found no significant difference in the incidence before (2.3 cases per million) or after (3.0 cases per million) a COVID-19 infection (adjusted IRR 1.35, 95% CI 0.64-2.85).

As for a potential cause between infection and retinal vein occlusion, Modjtahedi noted that COVID-19 can induce clotting.

"The associations we observed could also be from secondary events not directly related to the virus, such as worsening blood pressure or lack of physical activity after infection," he added. "This is something to consider because the peak incidence of retinal vein occlusion after COVID-19 was 6 to 8 weeks after the infection. There may be a delay in diagnosis, the pro-thrombotic state might last several weeks, or patients may have the condition due to secondary events."

The study "further strengthens the association between COVID-19 and retinal vascular occlusion," wrote K. Thiran Jayasundera, MD, MS, of the University of Michigan in Ann Arbor, and colleagues, in an . "However, the strength and consistency of this association would be enhanced by further evaluation including studies that access other large databases now available to provide a robust basis for causality and help determine recommended strategies for prevention and surveillance."

Jayasundera's group also noted that "one would expect that a severe COVID-19 infection would lead to more vascular occlusions; however, this may be negated by the anticoagulation regimens initiated in hospitalized patients with severe COVID-19."

Overall, the study found 12 cases of retinal artery occlusion and 43 cases of retinal vein occlusion in the 6 months before a COVID-19 infection. In the 6 months following infection, these numbers were 16 and 65, respectively.

Patients in the study were an average age of 41 years, 53.6% were women, 60.7% were Hispanic, and 20.3% were white. For comorbidities, 15.3% had a history of diabetes, 24.3% had hypertension, 20.6% were overweight, and 31.9% had obesity. Most of the patients (93.7%) did not require hospitalization for their COVID-19 infection.

COVID hospitalization was associated with an increased risk of retinal vein occlusion only in unadjusted analyses. Adjustments for the main analyses were made for various confounders, such as race, body mass index, and diabetes, and other factors.

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