A recent study included 50 eyes of 25 patients who had been hospitalized with COVID-19 and the same number of healthy controls. All underwent OCT-A in the early period after hospital discharge and six months later. Foveal vessel density (VD) and parafoveal VD values were measured from four quadrants (superior, inferior, nasal, temporal) of the superficial capillary plexus (SCP) and the deep capillary plexus (DCP).

COVID-19 patients showed significantly lower VD values in all parafoveal quadrants in both the SCP and the DCP at the initial checkup and in all parafoveal quadrants of the SCP and in the superior and inferior of the parafoveal quadrants of the DCP at a six-month follow-up, which is similar to what has been reported in previous studies. A decrease of choriocapillaris (CC) flow area values was also found over time.

This study is one of several that confirms COVID-19 has many lingering and long-term systemic effects, including in the lung and cardiac tissues. “In particular, long-term OCT-A examinations of tissues with high blood supply, such as the retina and choroid, show that persistent vascular flow changes can continue in the long-term due to the direct effects of the infection or the indirect effects of ongoing systemic changes,” the authors explained in their paper. “These findings are also seen in the acute period following COVID-19 infection.”

In addition, a vasodilation/vasoconstriction response varies depending on oxygen/carbon dioxide

imbalance. The authors explain this is is especially relevant for choroidal tissue “as it has the highest blood supply per unit in the body.”

“The decrease we found in CC flow area values when comparing the early period after COVID-19 infection and a six-month follow-up may have been due to the regression of the hypoxic environment in the CC leading to reactive vasoconstriction,” the authors noted in their study. “This change is perhaps an early indicator of local vascular improvement follow infection with SARS-CoV-2.”

The authors note the importance of performing appropriate follow-up for COVID-19 patients and suggest “multi-centered, long-term studies with large numbers of cases are needed to clarify the early and long-term retinal and choroidal vascular changes caused by COVID-19.”

Turker IC, Dogan CU, Dirim AB, etc. Evaluation of early and late Covid-19-indicted vascular changes with optical coherence tomography angiography. Canadian Journal of Ophthalmology. Epub ahead of print.