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

Area of Science:

• Ophthalmology
• Public Health
• Environmental Health

Background:

• Metal halide lights (MHLs) emit ultraviolet radiation (UVR).
• UVR exposure from MHLs necessitates the use of enclosed fixtures.
• A cluster of blurred vision cases among attendees at a light music event in South India prompted an investigation.

Purpose of the Study:

• To investigate a cluster of blurred vision cases among light music event attendees.
• To identify risk factors associated with the outbreak of eye-related symptoms.
• To determine the causal link between MHL exposure and the observed photokeratitis outbreak.

Main Methods:

• Door-to-door surveys were conducted to identify attendees with eye symptoms.
• Case descriptions included time, place, and person analysis; environmental inspection generated hypotheses.
• A cohort follow-up assessed the hypothesis of MHL exposure as the cause, calculating relative risk (RR) and confidence intervals (CI) based on seating location and exposure duration.

Main Results:

• 89% of interviewed attendees (284/319) developed bilateral photokeratitis.
• Higher attack rates were observed in females, those seated within 12 meters of the dais, and those with continuous MHL exposure (RR=2.5).
• Increased duration of MHL exposure significantly correlated with a higher risk of photokeratitis (P < 0.00001); MHLs with broken outer envelopes were identified.

Conclusions:

• Photokeratitis outbreak was strongly associated with UVR exposure from MHLs with damaged outer envelopes.
• Recommendations include the mandatory use of MHLs with enclosed fixtures to prevent future incidents.
• This study underscores the importance of proper MHL installation and maintenance for eye safety.