Determination of infrared radiation levels for acute ocular cataractogenesis.

One hundred pigmented rabbit eyes and ten primate eyes were exposed to infrared (IR) radiation in the 715 to 1,400 nm wavelength range and to the full spectrum output from a 5,000 W Xenon high-pressure source. The ocular exposures were evaluated independently with a slitlamp by two researchers and classified for ocular damage. The primary ocular lesions resulting from exposure to IR radiation were corneal, iritic, and lenticular. Corneal damage varied from epithelial haze to epithelial erosion but no endothelial damage was found. The iris showed stromal haze and swelling. Lenticular changes showed small white dots that, occur at the level of the anterior cortex. All lens damage depended on iris involvement. Ocular damage was related to the rate of delivery of the IR radiation since the data show that as the irradiance level increases, the radiant exposure threshold decreases. Exposures for the full spectrum were found to be additive for irradiance levels at 4 W.cm-2 and above. The threshold radiant exposures for the full spectrum of 750 J.cm-2 for the cornea, 1,000 J.cm-2 for the iris, and 2,000 J.cm-2 for the lens were essentially identical to the IR exposure thresholds for the same irradiance levels. The primate threshold radiant exposure was a factor of six above the respective rabbit thresholds.