An outbreak of bilateral photokeratitis and eyelid erythema following exposure to an artificial source of ultraviolet radiation, Tamil Nadu, India, 2018

Abstract

Background: Metal halide lights (MHLs) emit ultraviolet radiation (UVR) and should be used with enclosed fixtures. We investigated a cluster of blurred vision in a locality in South India reported among light music event attendees to identify risk factors. Methods: We searched for attendees with any eye-related symptoms by door-to-door. We described cases by time, place, and person and inspected the environment to generate a hypothesis. We followed-up the cohort of the attendees to examine the hypothesis of exposure to MHL as the cause of the outbreak. We computed relative risk (RR) and 95% confidence interval (CI) by comparing attack rates among attendees by seating location and duration of exposure. Results: Of the total 500 attendees, we could interview 319 (64%) and 89% (284/319) attendees developed bilateral photokeratitis (median age = 24 years [range: 2–80 years]). Attack rate was higher among female (92% [172/189]) than male (85% [110/130]). Attack rate among those seated within 12 meters from dais was higher (95% [241/253]) than the rest (65% [43/66]; RR = 1.5; 95% CI = 1.2, 1.7) and attack rate was higher among those continuously exposed to MHL (97% [268/277]) than others (38% [16/42]; RR = 2.5; 95% CI = 1.7, 3.7). The duration of exposure was associated with increased risk of bilateral photokeratitis (χ2 test for linear trend = 74; P < 0.00001). During the environmental inspection, we identified the use of MHL with a broken outer envelope. Conclusions: Photokeratitis was associated with exposure to UVR from MHL with a broken outer envelope. We recommended the usage of MHL along with enclosed fixtures.