Nigerian Postgraduate Medical Journal

: 2020  |  Volume : 27  |  Issue : 4  |  Page : 268--270

Routine slit lamp examination procedures: A risk for severe acute respiratory syndrome coronavirus 2 infection to eye care professionals

Ernest Ikechukwu Ezeh1, Elizabeth Dennis Nkanga1, Elijah Ndubuisi Chinawa2, Roseline Nkeiruka Ezeh3,  
1 Department of Ophthalmology, University of Calabar, Calabar, Nigeria
2 Department of Ophthalmology, University of Uyo Teaching Hospital, Uyo, Nigeria
3 Department of Ophthalmology, University of Calabar Teaching Hospital, Calabar, Nigeria

Correspondence Address:
Dr. Ernest Ikechukwu Ezeh
Department of Ophthalmology, University of Calabar, Calabar, Cross River State


Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a highly infectious coronavirus, has been rapidly spreading after its surge in China in December 2019. It is currently a global pandemic. A myriad of transmission routes have been documented, however established thus far, are respiratory droplet, contact and airborne transmissions. Susceptible persons at proximity, usually within 1–2 m, to infected persons are largely at risk of being infected. Unfortunately, health workers usually evaluate patients within this distance. Eye care professionals (ECPs) are faced with a higher risk scenario of being infected as they undertake routine clinical eye examination procedures at a close face-to-face proximity to patients, which place them at a high risk of respiratory droplets and aerosolised particles, particularly from asymptomatic and pre-symptomatic carriers. The slit lamp examination procedure is typically at a distance of between 0.25 m and 0.5 m. While undertaking certain procedures on the slit lamp, such as gonioscopy and slit lamp indirect ophthalmoscopy, the ECP holds the accessory lenses either directly on the patient's eye or at about 5–10 cm from the patient's face, respectively. The authors found it pertinent to articulate this narrative review article to guide slit lamp examination practice by ECPs during routine ophthalmic evaluation, with a view to reducing the spread of SARS-CoV-2 to ECPs. In conclusion, ECPs are at increased risk of infection due to high-risk scenarios for routine slit lamp examination procedures of the eye. Adherence to standard precautionary measures with slit lamp use is highly recommended.

How to cite this article:
Ezeh EI, Nkanga ED, Chinawa EN, Ezeh RN. Routine slit lamp examination procedures: A risk for severe acute respiratory syndrome coronavirus 2 infection to eye care professionals.Niger Postgrad Med J 2020;27:268-270

How to cite this URL:
Ezeh EI, Nkanga ED, Chinawa EN, Ezeh RN. Routine slit lamp examination procedures: A risk for severe acute respiratory syndrome coronavirus 2 infection to eye care professionals. Niger Postgrad Med J [serial online] 2020 [cited 2021 Jan 19 ];27:268-270
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Full Text


Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is new strain of coronavirus causing a highly contagious viral disease, referred to as coronavirus disease 2019 (COVID-19).[1] Infections by other coronaviruses such as SARS-CoV and Middle East respiratory syndrome coronavirus,[1] have been reported in the past in humans, but SARS-CoV-2 was first documented in human beings in Wuhan, China, in December 2019 and has spread rapidly to the rest of the world.[2]

COVID-19 manifests clinically as an asymptomatic or symptomatic disease. The spectrum of symptomatic disease ranges from loss of smell, loss of taste, common cold to more severe respiratory and multi systemic diseases.[1],[3],[4]

SARS-CoV-2 mainly spreads through droplets of saliva, nasal and oral discharge when a person infected with SARS-CoV-2 coughs, sneezes or talks.[5] Evidence of airborne transmission has recently been established.[6],[7] These transmission routes portent increased risk of infection for healthcare workers, who routinely assess patients at close distance. A previous review on SARS outbreaks by the World Health Organization noted that healthcare workers accounted for 20% of the infected.[5] Much more, eye care professionals (ECPs) bear close face-to-face proximity during routine slit lamp examination [Figure 1]. As of 10th May 2020, 13 ophthalmologists have died from COVID-19 globally.[8]{Figure 1}

The authors found it pertinent to articulate this review to guide slit lamp examination practice during routine ophthalmic evaluation, with a view to mitigating the transmission of SARS-CoV-2. The slit lamp examination procedure was chosen for this article for the following reasons: it is central in almost all ophthalmic examination, with the use of the accessory lens like +90 D. The use of direct ophthalmoscopy can be avoided, as well as its use in therapeutics such as slit lamp-delivered lasers. In writing this narrative review article, the authors searched using the words SARS-CoV-2, ophthalmologist, optometrist, eye care workers, eye care practitioners, droplet transmission, aerosol transmission, coronavirus disease 2019 (COVID-19), ophthalmic examinations and slit lamp examination, to find relevant articles from December 2019 to August 2020 in four databases (PubMed, Web of Science, Google Scholar and Scopus).

 Epidemiologic Facts

Quite importantly, it is the documented fact that SARS-CoV-2 is transmittable from the spectrum of asymptomatic, pre-symptomatic and symptomatic COVID-19 patients.[9],[10],[11],[12],[13] Up to 44% of transmission likely occur before onset of symptoms.[10] Up to 80% of cases remain asymptomatic.[14],[15],[16] Li Wenliang, an ophthalmologist in Wuhan, China, who raised alarms on the novel coronavirus, and later died from the disease, was reported to have been infected by an asymptomatic acute angle-closure glaucoma patient.[13] Furthermore, nearly 86% of SARS-CoV-2 infections are unidentified, but about 55% of these were contagious.[17] These undocumented infected persons are more common than the current testing levels that can account for.[17] This may be particularly true in developing countries where testing capacity is still extremely low. These persons may serve as a great reservoir for transmission than tested positive, symptomatic patients. All these facts constitute a critical risk for high infectivity rate for healthcare workers, in particular, and for the public, in general.

 Transmission Routes of Severe Acute Respiratory Syndrome Coronavirus 2 during Slit Lamp Examination Procedures

The settings for slit lamp examination constitute at-risk scenarios for the transmission of SARS-CoV-2. These include:

Direct droplet transmission: The close face-to-face proximity, at distance between 0.25 m and 0.5 m, places the ECP a risk of respiratory droplet and aerosol transmission of SARS-CoV-2Indirect droplet transmission: It is also referred to as fomite infectivity. This can occur under the following settings:

During slit lamp examination procedures, the patient has contacts with surfaces of the slit lamp machine, such as the chin rest, hand rest and fore head band. SARS-CoV-2 can remain viable on surfaces for 2–3 days, increasing the chance of fomite infectivity[18]Slit lamp shield use: The use of slit lamp shield has been advocated and is in current use as a preventive strategy against COVID-19 spread. Respiratory droplets also settle on this shield, thus constituting an additional fomite. Researchers have also reported that aerosols congregate at a high density around the examiner's nose and mouth, likely due to leaks around the slit lamp oculars which serve as attachment for the shield[19]The ECP may sometimes handle accessory lenses, such as the goniolens and + 90 D lens, on the patient's eye or at about 5–10 cm to the face to perform further examinations while using the slit lamp machine. This brings the ECP's hand at direct contact with tears as well as at a very proximity to the patient's nose and mouth. Respiratory droplet, droplet nuclei and tears, which are the infective vehicle,[7],[20] could settle on the ECP's hands.Examination room setting: Slit lamp examination procedures are preferably done as dark room or dim light procedures. This necessitates closure of blinds or windows and/or doors. This poorly ventilated setting increases the chances for the formation of an infectious toxic cloud.[21]

 Advisory on Slit Lamp Use during Para-Covid Era

Slit lamp examination should be undertaken on patients in whom it is absolutely indicated; such as cases of sudden or recent visual loss, painful red eye, rapidly progressive glaucoma, ocular tumours, ocular trauma, patients on antiglaucoma medications, patients on prolong steroid eye drops and patients at high risk of retinal diseases, e.g., diabetics and high myopia.[22]

Ruiz-Lozano et al.[23] as well as Gharebaghi et al.[24] have articulated a concise advisory on slit lamp examination practice in a routine ophthalmic setting as follows: before the slit lamp examination, slit lamp shield should be installed, the ECP and the patient must wear protective gears which include face mask, preferably N95 masks for the ECP, 3 ply face masks for low-risk patients and N95 masks for high-risk patients. The ECP should wear protective eye and face coverings such as eye goggles or face shield. Both the ECP and the patient should appropriately wash their hands, while the ECP additionally puts on a new pair of gloves for each patient being examined. During the slit lamp examination, the ECP and the patient must not cough, talk or sneeze. Preferably, the examiner should use a wooden swab stick while manipulating the eyelids. Contact tonometry should be avoided; if absolutely necessary, the use of disposable tips is highly recommended or the reusable tips are sterilised before and/or between uses. Same applies for other accessories such as the goniolens, indirect fundus lens, e.g., +90 D, +78 D and 3-mirror lens. After the slit lamp examination, the slit lamp shield as well as contact surfaces of the machine must be cleaned and disinfected.[23],[24] The recommended disinfectant solutions are 1.5 tablespoons of household sodium hypochlorite per litre of water or with 70% or more ethyl alcohol and isopropyl alcohol solutions.[25]

Ventilation protection measures should be employed in the ophthalmic examination room. The central principle is to ensure adequate dilution and replacement of exhaled air, thereby negating the build-up of viral contamination and therefore lowering the infectious dose.[21] These measures include:

Simply, opening doors and windows.[23] Overhead fans may offer some benefitsInstallation of a heating, ventilating and air-conditioning unit system[21]Avoid air recirculation. However, in settings where it is not feasible, local air cleaning and disinfection systems, such as germicidal ultraviolet, may be installed.[21]


The SARS-CoV-2 is a highly contagious emerging strain of coronaviruses and portends a targeted danger to ECPs. ECPs are at increased risk of infection due to the high-risk scenarios for routine slit lamp examination procedures of the eye. Adherence to standard precautionary measures with slit lamp use is highly recommended.

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Conflicts of interest

There are no conflicts of interest.


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