ABSTRACT
Purpose:
This study aimed to use computational models for simulating the movement of respiratory droplets when assessing the efficacy of standard slit-lamp shield versus a new shield designed for increased clinician comfort as well as adequate protection.
Methods:
Simulations were performed using the commercial software Star-CCM+. Respiratory droplets were assumed to be 100% water in volume fraction with particle diameter distribution represented by a geometric mean of 74.4 (±1.5 standard deviation) μm over a 4-min duration. The total mass of respiratory droplets expelled from patients’ mouths and droplet accumulation on the manikin were measured under the following three conditions: with no slit-lamp shield, using the standard slit-lamp shield, and using our new proposed shield.
Results:
The total accumulated water droplet mass (kilogram) and percentage of expelled mass accumulated on the shield under the three aforementioned conditions were as follows: 5.84e-10 kg (28% of the total weight of particle emitted that settled on the manikin), 9.14e-13 kg (0.045%), and 3.19e-13 (0.015%), respectively. The standard shield could shield off 99.83% of the particles that would otherwise be deposited on the manikin, which is comparable to 99.95% for the proposed design. Conclusion: Slit-lamp shields are effective infection control tools against respiratory droplets. The proposed shield showed comparable effectiveness compared with conventional slit-lamp shields, but with potentially enhanced ergonomics for ophthalmologists during slit-lamp examinations.
Keywords:
Ophthalmologi sts; Coronavirus infections/prevention & control;Pandemics; Lipid droplets; SARS-CoV-2; Slit-lamp; Computer simulation; Protectivedevices; Equipment design
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(A) Illustration of the measurements of the proposed shield. (B) Left image illustrates how the proposed shield will fit around the slit-lamp. The right image displays a 3D image of the proposed shield. These are the original figures drawn by the author; therefore, permission is granted for publishing and reproducing this figure.
The total droplet mass expelled by the emitter and accumulated on the head when no protection was used throughout the whole simulation (a) and mass accumulated on the head during the first 1 s of solution (b). (c) And (d) show the total droplet masses accumulated on shield (a) and manikin (b) surfaces, respectively, throughout the simulation case with the standard shield. Total aerosols masses accumulated on shield (e) and manikin surfaces throughout the simulation case with the proposed shield (f). Original figures with permission from Edinilson Costa.
(A) Aerosol droplet distribution colored by residence time for simulations with no shield protection, at solution times of (i) 0.20 s, (ii) 5 s, (iii) 20 s, (iv) 50 s, (v) 100 s, and (vi) 240 s. (B) Aerosol droplet distribution colored by residence time for simulations with standard shield protection, at solution times of (i) 0.20 s, (ii) 5 s, (iii) 20 s, (iv) 50 s, (v) 100 s, and (vi) 240 s. (C) Aerosol droplet distribution colored by residence time for simulation with proposed shield protection, at solution times of (i) 0.20 s, (ii) 5 s, (iii) 20 s, (iv) 50 s, (v) 100 s, and (vi) 240 s.These are original figures drawn by the author; therefore, permission is granted for publishing and reproducing this figure.