Seeking clarity on retinal findings in patients with COVID-19 – Authors' reply

We are thankful for the comments in response to our Correspondence about retinal findings in patients with COVID-19.¹ COVID-19 is a challenging new disease that has raised many questions around unusual findings.

Regarding the comorbidities of the 12 patients,¹ seven patients had no comorbidities, one had controlled type 2 diabetes and high blood pressure, two had high blood pressure with good clinical control, one had a history of dyslipidaemia, and one had ankylosing spondylitis, controlled with adalimumab, and no previous history of ocular involvement.

A major concern raised was that the reported hyper-reflective lesions at the level of the ganglion cell and inner plexiform layers were, in fact, cuts through normal retinal blood vessels. To ensure that this was not the case, we excluded vertical optical coherence tomography (OCT) scans from our analysis and used only horizontal scans to avoid vessel crossings.

Since our original Correspondence,¹ we have examined more than 150 patients who tested positive for COVID-19 and whose disease ranged in severity, from asymptomatic to requiring admission to intensive care. We have refined our examination protocols. Using the B-scan flow overlay feature of OCT angiography, we found an absence of blood flow within the retinal lesions of many patients, differentiating these lesions from blood vessels with active blood flow. We observed similar findings outside of the posterior pole. Additionally, we have noticed fewer cotton wool spots and microhaemorrhages with time in these patients.

More than 6 months has passed since the outbreak of severe acute respiratory syndrome coronavirus 2, and lots of new information has emerged describing COVID-19 pathophysiology. These retinal lesions appear to be part of a widespread, ischaemic, microvascular process, the effects of which have been reported in other parts of the body,2, 3, 4, 5 as Pradeep Venkatesh suggested.

Following up these patients closely is essential, and we understand the urgency of finding answers but also agree with the necessity for caution when interpreting new information. We intended our Correspondence to call attention to the need for careful evaluation of the fundus because therein lies a unique opportunity to analyse the body's microvasculature in vivo. We are collecting more information and intend to describe these in the medical literature in due course.