COVID-19 Resource Center

COVID-19 Resource Center


Hui KPY, et al. Lancet Respir Med. 2020;doi:10.1016/S2213-2600(20)30193-4.

Disclosures: Mah reports no relevant financial disclosures.
June 08, 2020
8 min read

Q&A: Transmission of COVID-19 and what it means for ophthalmic safety


Hui KPY, et al. Lancet Respir Med. 2020;doi:10.1016/S2213-2600(20)30193-4.

Disclosures: Mah reports no relevant financial disclosures.
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A study recently published in The Lancet Respiratory Medicine by Kenrie P.Y. Hui, PhD, and colleagues compared infection, replication competence, tropism and pathogenesis of the novel coronavirus SARS-CoV-2 with other respiratory pathogens.

Among their findings, the researchers reported the conjunctival epithelium may be an additional portal of infection for the virus.

Francis S. Mah, MD infographic pull quote

Ophthalmologists are at risk for infection of the virus due to the face-to-face nature of examinations and ocular surgery. Healio/OSN asked Francis S. Mah, MD, an OSN Cornea/External Disease Board Member, to discuss the findings of the study and to share his thoughts on how ophthalmologists can keep themselves, their employees and their patients safe during the COVID-19 pandemic.

Q: What were your general thoughts on the findings of the study?

A: I think it fits in with the growing knowledge of SARS-CoV-2 in terms of the epidemiologic information that we are hearing, for example, out of China, Spain and Italy, about the possibility of transmission of the virus through the mucous membranes of the eye. There have been several studies that show you can culture the virus from infected patients, and we know about ACE-2 as a receptor for SARS-CoV-2 which is present in the human conjunctiva.

This study shows from an experimental point of view that you can actually infect humans through their conjunctiva. There is ACE-2 on the human conjunctival cell. This study supports the growing knowledge of the possibility of ocular transmission.

This mode of transmission is not 100% accepted. There still seems to be some controversy because we have not figured out every aspect of when it is present in tears and when somebody could become infected by ocular transmission.

Q: What are your thoughts on the route of transmission of the disease for ophthalmologists? This study shows the conjunctival epithelium can be a potential portal of infection, but can this be transmitted through tears?

A: In general it seems that at least for COVID-19-positive patients who have ocular symptoms, and approximately 1% of the infected patients do from early reports from China, every study has shown that there are positive cultures from the conjunctiva and the tears from those patients. Not every patient with ocular symptoms, but definitely enough positive cultures to be concerned.

Going along with the findings from this study, it looks like the virus could be transmitted from eye to eye, and why not? The conjunctiva is a mucous membrane, so if a patient touches their tears, then a provider touches their own eyes with contaminated fingers, they could infect themselves.


That is mode of transmission that is suspected for the whistleblower in China. He was a glaucoma specialist, and the thought is that he was probably seeing an asymptomatic or presymptomatic coronavirus patient and probably got infected through his conjunctiva. With the evidence we have, we should assume this is a possible scenario.

Q: In the operating theater, how can an ophthalmologist protect themselves during surgery? Would the necessary personal protective equipment (PPE) be detrimental to vision during a procedure?

A: How do we safely see patients? How do we prevent the spread? There are a few aspects for this. In the clinic, it depends on the situation and access to PPE, specifically, N95 masks, as far as the best way to prevent infection. The American Academy of Ophthalmology is recommending that ophthalmologists wear medical masks in general at the very least. The N95 would be preferred, even in the clinic, but a surgical mask is better than nothing. In addition to the mask, due to the growing evidence, including the study we mentioned, all clinicians should wear goggles or a shield in the clinic because we are in such close proximity to patients and approximately 20% to 30% of coronavirus patients are asymptomatic.

As far as the operating room, the highest person at risk will be the anesthesiologist. The recommendation for the anesthesiologist and ophthalmic surgeon is to wear an N95 mask depending on the availability.

The second recommended PPE is tight-fitting goggles or a shield. Glasses might be a compromise or acceptable surrogate measure of protection. As far as doing surgery, if you are not used to wearing glasses, it can be difficult. It is impossible, I would say, to operate with a shield, so there must be a balance between safety of transmission and providing excellent care for the patient.

Between 20% to 30% of people are asymptomatic, and another 20% to 30% have mild infections or are presymptomatic. You have a lot of people out there potentially spreading the virus.

In our system, we are making everyone who is having surgery take a coronavirus polymerase chain reaction test, but you can definitely get a false negative from the test and give yourself a false sense of security. Again, in ophthalmology, we are so close to patients and have tears that are splattering and aerosolizing in the environment, so I think it definitely makes sense for ophthalmic surgeons to protect themselves with N95 masks. The second PPE would be to wear goggles, but again, understand that the primary purpose in the operating room is to take care of the patient and provide excellent care. It is a delicate balance.


There are two points about masks in general I would like to talk about. The first is that you need an excellent fit. Things such as facial hair, beards and so forth are popular, especially now with the lockdown. However, a good fit is critical for any and all masks including an N95, as well as medical and cloth masks. Facial hair has been shown to allow the transmission of small particles around the mask. Therefore, that difficult-to-obtain N95 mask is not protecting those folks who have facial hair. It is like having seat belts but not wearing them but expecting the same level of safety.

Secondly, there are commercially available masks that have valves in them. The valve masks were developed by 3M, the initial developers of the N95 masks, for miners and manufacturers. The valve is a one-way valve for hot environments, so if you were to breathe out, your exhalation is not inhibited. On inhalation, you would still get the benefits of an N95 mask if it fits properly. For the purposes of coronavirus prevention and the pandemic, these valved masks are only doing half of what a mask is supposed to be doing. If you have an asymptomatic surgeon or patient wearing one of these and is positive for the coronavirus, they are exhaling and spreading the virus as if they did not have any facial covering. The purpose of facial coverings is twofold, to protect the person wearing the mask and to prevent the spread from an asymptomatic person to naive people. With valved masks, there is only half the benefit.

Q: What other precautions do ophthalmologists need to take to keep themselves safe during the pandemic?

A: We have to critically evaluate every step of the clinic, operating room and waiting room. The way to reduce the spread is to realize the way it is transmitted, by contact and aerosolization. Anything that is going to aerosolize, anything as far as contact, we have to try to minimize or eliminate.

The spread can start right away. In our clinic, we call the patients a day ahead and ask about any symptoms they may have, such as coughing, sneezing, diarrhea and eye symptoms, and ask if they have come into contact with anyone who has had the virus. We require patients show up to the front door of our building wearing a mask. If they have symptoms, we tell them not to come in and for the patient to call their primary care doctor.


At the front door of the building, the patients are asked the same questions and have their temperature taken. As an aside, a temperature check is a good thought, but if a patient has taken Tylenol or Advil, that will reduce fevers. You should ask if they have taken either if you are planning to take temperatures as a screening method. Only patients are allowed into the building; caretakers are asked to wait outside or in their vehicles. When the patient gets to our check-in counter, our front desk person is wearing a mask and gloves with a plexiglass shield between them and the patient.

We have reduced schedules and taken out all magazines, coffee, water and toys from our waiting rooms. We have blocked off chairs in our waiting rooms so that we have social distancing. Our schedules are reduced so even if we are an hour behind, we will not fill up the chairs in the waiting room. Finally, we are having people wait in their cars and texting them if the waiting rooms get backed up.

In the clinic, all staff are required to wear a mask and gloves. Currently, we are not allowing pharmaceutical representatives into the building.

We inform patients we limit unnecessary discussions in the examination rooms because talking can potentially aerosolize the virus.

We have a non-contact tonometer to measure pressures in addition to other methods. Anyone who has any ocular symptoms suspicious for an infection, we defer the non-contact method of measuring IOP. This is generally an excellent policy whether one is concerned about coronavirus or any infectious pathogen of the eye. We have a face shield, gloves and masks for all of the technicians.

After we see each patient, we are completely wiping down the entire room. Any surface that can be touched, we are using bleach wipes.

We are doing all of that for our clinic, slowly increasing our numbers. We have incorporated telemedicine visits into our clinic, and we have been doing many more video visits with patients, especially for follow-up appointments.

For the operating room, everyone gets a COVID-19 test 24 to 48 hours before their scheduled surgery. Patients are required to wear masks to the building. The mask is lowered just before the sterile skin preparation with povidone-iodine and raised back up at the conclusion of the surgery when the surgical drapes are removed. Nonessential caretakers are not allowed into the building. They are called from their vehicles when the patient is being discharged, and the patients are discharged with postoperative instruction given in the driveway with the caretakers. We have reduced our operating schedule to be able to clean and disinfect the operating rooms, as well as provide social distancing in the waiting rooms and preoperative and postoperative holding areas.


In certain areas, you may want to test patients twice or get a chest X-ray before surgery. Our prevalence has been pretty low, currently about a 2% positive testing rate, but in areas that are 20% to 30% positive rates or higher, you may want to have more stringent requirements to enter the operating room.

Q: Is there anything else you would like to say based on the results of the study or how ophthalmology will be practiced moving forward in this new climate?

A: I personally think that there are going to be some things that are held over — a new legacy, the coronavirus legacy. I used to shake everyone’s hand when they came into the clinic, but I do not know if I will be shaking many hands after this. In terms of disinfecting the lanes after a patient visit and so forth, I think the process is a good habit to maintain. As far as distancing, 3 feet instead of 6 feet has been shown by more recent studies to be adequate; this could be doable when this is all over. As far as wearing a mask, we in the U.S. and the Western world in general have not been as accepting of this practice as other parts of the world, but the benefits are being reported in the peer-reviewed literature more and more, so we might approach a point in the near future of donning a mask especially if we do not feel completely healthy.

I think there will definitely be some areas where we are doing some of the things that we probably should have been doing all along. Because of the coronavirus, the barriers have been broken. People will have a lot more common sense about the possible spread of any communicable or transmissible disease.