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

Purpose: The global COVID-19 pandemic has resulted in a renewed focus on the importance of personal protective equipment (PPE) and other interventions to decrease spread of infectious diseases. While several ophthalmology organizations have released guidance on appropriate PPE for surgical procedures and ophthalmology clinics, there is limited experimental evidence demonstrating the efficacy of 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. Design: Experimental cough simulation using a fluorescent surrogate of respiratory droplets during an ophthalmic slit lamp examination. Methods: Setting: Single-center Study Population: Patient Simulation Main outcome 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 during the model slit lamp examination. Coughing with a mask resulted in the most significant decrease in droplets, however, particles still escaped from the top of the mask. Coughing with the slit lamp shield alone blocked most of forward particle dispersion; however significant distributions of respiratory droplets were found on the slit lamp joystick and table. Coughing with both mask and slit lamp shield resulted in the least dispersion to the simulated examiner. Scanning electron microscopy demonstrated particle sizes of 3-100μm. Conclusions: Masking has the greatest effect in limiting spread of respiratory droplets, while slit lamp shields and gloves also contribute to limiting exposure to droplets from SARS-CoV-2 during slit lamp examination.