Abstract
Purpose :
The emergence of COVID-19 has introduced new challenges to eye care practitioners, not the least of which is mask-related fog on slit lamps, condensing lenses, phoropters, and perimeters. In this case series, we examine the effect that phoropter lens condensation has on visual acuity and contrast sensitivity and evaluate the efficacy of an anti-fog device at preventing condensation on a phoropter lens.
Methods :
Snellen visual acuity (VA) and contrast sensitivity (CS) measured across four spatial frequencies (3, 6, 12, 18 cycles/degree) with Vector Vision (Guardion Health Sciences, San Diego, CA) were examined. Both VA and CS were evaluated monocularly in healthy subjects wearing KN95 masks, first while viewing through a Lorgnette occluder as a control (no lens), then through a phoropter. When using the phoropter the +0.125 lens was deployed bilaterally to emulate lens presence during refraction while minimally affecting refractive error. During testing the right lens of the phoropter was room temperature (20°C) and the left lens was heated to 37-40°C using a flexible electric heating strip. Subjects were not masked to which side was heated.
Results :
Ten eyes of 5 subjects (2 female, 3 Male, mean age 32.4yr) were evaluated. Baseline mean LogMAR VA (±SD) was 0.00±0.12 in the right eye (OD) and 0.04±0.16 in the left eye (OS). Mean CS area under the curve (AUC) was 6.7±0.4 OD, and 6.7±0.5 OS. There was no difference in baseline VA or CS between left and right eyes (both P>0.3). Eyes re-tested through the heated phoropter lens had mean LogMAR VA of 0.02±0.1 and CS AUC of 6.8±0.7 and were not different from baseline (both P>0.2). However, eyes re-tested through the unheated phoropter lens (control) showed mean LogMAR VA of 0.09±0.1, and CS AUC of 5.0±1, both of which were significantly worse than baseline (both P<0.05). All subjects reported various amounts of condensation on the room temperature lens and no condensation on the heated lens.
Conclusions :
An electrically heated adhesive fabric eliminated mask-related fog on the phoropter lens and prevented fog-associated deficits in VA and CS. The utilization of lens heating devices on microscopes, perimeters, and phoropters will alleviate fogging introduced by measures intended to limit the spread of COVID-19.
This is a 2021 ARVO Annual Meeting abstract.