As the COVID-19 pandemic has now ravaged the world for more than a year, much of the concern and research has centered on the respiratory symptoms of SARS-CoV-2 infection, and rightfully so. However, there has been very little media or research attention dedicated to the potentially significant impacts of SARS-CoV-2 on the visual system and the eyes.
There has been prior evidence of the negative impacts of coronaviruses on eye health. In 2004, physicians Seah and Agrawal reported that 17% of those infected with HCoV-NL63 – a virus similar to SARS-CoV-2 – also presented with conjunctivitis, which is an inflammation of the eye’s outer mucous membrane layer and is commonly known as pink-eye . More recently, one of the earliest COVID-19 patients also presented with conjunctivitis before even being diagnosed with the virus . Additional work has found conjunctivitis to be the only diagnostic indicator of COVID-19, as well as the only symptom of COVID-19, in five different patients . It is clear that coronavirus particles can attach to the mucous membranes of the eye, and thus can likely spread inter-ocularly. Thus, it is critically important that plastic face shields and goggles be used in medical care to prevent infection.
However, coronaviruses have been shown to do even more harm than conjunctivitis. In 1991, researchers Robbins, Detrick and Hooks found that the coronavirus mouse hepatitis virus (MHV) can lead to retinopathy in mice . In their study, significant damage to pigments within the photoreceptors was observed, irrespective of how the virus was administered (intraocularly, nasally, etc.). Despite individual variance between mice, damage was consistently present .
There is some speculation about the mechanism via which coronaviruses attack the eyes. Research has suggested that coronaviruses may utilize the ACE-2 receptor, a key component of the renin-angiotensin system (RAS) that maintains blood pressure within the eye as well as the body. The eye’s RAS is independent of the body’s, and plays an important role in vision. However, ACE-2 is not largely found in the conjunctiva, where SARS-CoV-2 can be found, so this merits further exploration .
On a broader scale, more people have been working from home than ever before. This means increased time behind screens and computer monitors. Prolonged exposure to the high frequency, short wavelength light emitted from these devices has been demonstrated to cause damage to the pigments in the eye’s photoreceptors, just as the actual virus can. Over time, individuals with prolonged exposure can develop computer vision syndrome (eye strain and fatigue from substantial computer use) and are at risk for a multitude of health concerns, most notably age-related macular degeneration .
Additionally, routine vision care has largely been impacted by lockdowns and quarantine requirements. There is a substantial risk of viral transmission during routine eye exams as well as surgical procedures. Optometrists and ophthalmologists must both come into close contact with their patients, placing them at potential risk. Recommendations made by professional bodies such as the American Academy of Ophthalmologists early on in the crisis suggested that elective procedures be delayed and certain procedures be enacted to minimize risk [5,6]. Yet there are possible unknown consequences of these delays in elective treatment . Non-emergency conditions can quickly precipitate into more serious conditions. Furthermore, potential disorders may go undetected with a reduction in routine eye exams, which frequently detect diabetes, hypertension, cancers and a plethora of other ocular and systemic disorders.
It is thus abundantly clear that COVID-19 is not simply a respiratory disease, but also an ocular one. Considerably more research must be directed towards the visual health impacts of coronaviruses. Furthermore, the long-term impacts of COVID-19 must be examined, particularly for those who may develop serious retinopathy.
Edited by: Sophia Xiao
Illustrated by: Lucy Chen