Threshold Ocular Exposure to Near Infrared Radiation for Causing Acute Opacification in the Rabbit Lens

Surveys and epidemiological studies have reported an increased prevalence of cataracts in the glass and steel industries, which are associated with exposure to intense infrared radiation (IR). Indeed, animal studies have demonstrated that IR exposure can produce acute changes in the crystalline lens that are likely to lead to cataract formation. However, little is known about threshold IR exposure for causing acute cataractous changes, which is important in the prevention of IR-induced cataract, especially as a basis for short-term IR exposure limits. Previously, we exposed rabbit eyes to 808 nm wavelength IR at different irradiances for 6 min to determine the threshold irradiance to cause acute lens opacification. Presently, we similarly determined the threshold irradiance for exposure durations of 3 min, 1 min, 30 s, 10 s and 4 s. The threshold irradiance increased steadily with decreasing exposure duration, from 1.1 W cm^-2 at 6 min to 4.1 W·cm^-2 at 4 s. These threshold values are consistent with ICNIRP exposure limits to avoid IR-induced cataract formation in the tested range of exposure duration, but suggest that it may be necessary to lower the exposure limits for shorter exposure durations.