Assessment of respiratory droplet transmission during the ophthalmic slit lamp exam: a particle tracking analysis (preprint)

ABSTRACT

Importance The global COVID-19 pandemic, which began in late 2019, has resulted in a renewed focus on the importance of personal protective equipment (PPE) and other interventions to decrease the spread of infectious diseases. While several ophthalmology organizations have recently released guidance on appropriate PPE for surgical procedures and ophthalmology clinics, there is limited experimental evidence demonstrating the efficacy of the various interventions that have been suggested. In this study, we evaluate high-risk aspects of the slit-lamp exam and the effect of various PPE interventions. Objective To determine the effectiveness of surgical masks, slit lamp shields, and gloves in decreasing the spread of large droplets in an ophthalmology clinical setting and evaluating high-risk sources of contamination. Design Experimental cough simulation using a fluorescent surrogate of respiratory droplets during an ophthalmic slit lamp examination. Setting Single-center Participants Patient Simulation Main outcomes and measure(s) Presence of fluorescent particles in the air near or on slit lamp and simulated slit lamp examiner. Results Simulated coughing without a mask or slit lamp shield resulted in widespread dispersion of fluorescent droplets on the model slit lamp examination. Coughing with a mask resulted in the most significant decrease in fluorescent droplets, however, particles were still seen to escape from the top of the mask. Coughing with the slit lamp shield alone blocked the majority of forward particle dispersion; however significant distributions of respiratory droplets were found on the slit lamp joystick as well as table. Coughing with both mask and slit lamp shield resulted in the least dispersion on to the simulated examiner. Scanning electron microscopy demonstrated particle sizes of 3-100μm. Conclusion and relevance Masking has the greatest effect in limiting spread of respiratory droplets, while slit lamp shields, and gloves also contribute to limiting exposure to respiratory droplets from SARS-CoV-2 during slit lamp examination. Key Points Question How effective are certain personal protective equipment and interventions in the clinic in preventing respiratory droplet spread? Findings Simulating patient coughing during the slit lamp exam demonstrated that masking appeared to be the most effective intervention to prevent spread of respiratory droplets. Slit lamp shields and gloves were also effective in decreasing exposure to respiratory droplets. Meaning This study confirms the importance of masking, slit lamp shields, as well as gloves as important interventions to limit exposure to respiratory droplets from respiratory viruses such as SARS-CoV-2.