When it comes to ocular health, the COVID pandemic may be more than simply a “sight for sore eyes.” In fact, the latest research suggests the virus may actually target the retina and replicate within its cells – a troubling concern, warns Deborah Zelinsky OD, a Chicago area optometrist and an internationally noted expert on retinal processing.

Initial pandemic-related ocular studies, including one published in 2020 in BMJ Open Ophthalmology (https://bmjophth.bmj.com/content/5/1/e000632), indicated COVID can lead to development of pink eye (conjunctivitis), light sensitivity, and sore and itchy eyes – all temporary conditions. 

But Dr. Zelinsky refers to more disconcerting scientific reports, including one first presented online in 2021 by bioRxiv (https://www.biorxiv.org/content/10.1101/2021.10.09.463766v1). In it, authors indicate the COVID virus seems able to infect the photoreceptor and ganglion cells in the retina and replicate in them, potentially leading to visual impairments, including blindness. Other researchers agree, among them a team of Italian and Australian investigators who, in a study published in a 2020 issue of EClinicalMedicine (doi.org/10.1016/j.eclinm.2020.100550) state “COVID-19 can induce important changes at the level of the retina, most of them affecting the retinal vasculature…particularly [the] veins.”

As important as are these discoveries of COVID’s danger to eyesight, it is the virus’ potential to cause long-term neurological problems that remains of greater concern to Dr. Zelinsky.

“The retina serves as a critical component of the entire central nervous system, which includes brain and spinal cord. It acts as a primary portal for information to the brain. Environmental signals in the form of light pass through the retina and convert into electrical signals that propagate through neurons and interact with critical brain structures,” says Dr. Zelinsky, founder and executive research director of the Mind-Eye Institute in Northbrook, Illinois. “What we do not know at this point is whether COVID infection of retinal cells might interfere with retinal processing, or worse yet, brain processing.”  Many studies are beginning to show linkages between retinal health and brain health.

Retinal processing refers to the brain’s ability (partially beneath a conscious level of awareness) to filter signals passing through the retina and then forward the filtered version for further brain processing. Through this “further processing,” the brain combines retinal signals with other sensory signals (from hearing, smell, taste, and touch), synthesizes the information, and then enables a person to react and respond in ways that depend on the individual’s many internal sensory signals.

Retinal signals interact not just with the visual cortex but affect other, significant regions of the brain as well, like the limbic system, the cerebellum, mid-brain, thalamus, hypothalamus, and brainstem. “The implication is that any disruption to the functioning of retinal cells – including  COVID infection — may have long-term impact on basic physical, physiological, and even psychological processes regulated by the brain. Those processes involve motor control, posture, emotion, and decision-making abilities, among others,” Dr. Zelinsky explains.

Dr. Zelinsky and the Mind-Eye Institute have gained worldwide attention for groundbreaking investigative and clinical work involving retinal processing. Indeed, expanding knowledge about the retina and application of advanced optometric science have enabled the Institute to achieve well documented, clinical successes in using customized, therapeutic eyeglasses to help diminish symptoms of traumatic brain injury, concussion, stroke, and other neurological disorders in some people. These “brain” glasses also have proven effective in building undeveloped processing skills in children – and adults – with learning deficiencies, including those “on the spectrum.”

By varying the amount, intensity, and angle of light dispersed on the retina, brain glasses often help restore synchronization to patients’ disrupted sensory systems. The lenses also can alter patients’ awareness, attention, and understanding of what is happening in the world around them; enhance visual processing skills; and frequently bring a return of comfort and relief to people with retinal dysfunctions.

“The retina is the only part of the brain that is easily visible and accessible to professionals, yet its importance has long been undervalued,” Dr Zelinsky emphasizes. “The ability of the COVID virus to invade this critical structure is of increasing concern to scientists and health professionals in general. Future studies and experience with the virus should present us a clearer picture of the virus’ potential long-term impact on brain function.”