Study of corneal lesions induced by 1,318-nm laser radiation pulses in Dutch belted rabbits (Oryctolagus cuniculus).

BACKGROUND AND PURPOSE: Use of high-energy near-infrared lasers is becoming more prevalent in today's industries, such as technology, medicine, and military operations. Despite wide-range use of these lasers, threshold, median effective dose (ED50), and the mechanism of laser-tissue interaction are not well defined at the 1,318-nm wavelength for human corneal exposures. The goals of the study reported here were to establish the ED50 for single-pulse, 1,318-nm laser exposures on the Dutch Belted rabbit cornea and to characterize microscopic changes. Results of this study were then compared with those of previous corneal studies. METHODS: A neodymium:yttrium aluminum garnet (Nd:YAG) laser was used to deliver single 1,318-nm wavelength pulses to the corneas of 10 female Dutch Belted rabbits (Oryctolagus cuniculus). Single pulses of 0.5-ms duration and radiant energy ranging from 116 to 2,250 J/cm2 irradiated the exposure sites. Sites were clinically evaluated for presence of a lesion at one hour and 24-h after exposure. Results of the 24-h evaluation were used to determine the (ED50). Corneas were subsequently collected at the 24-h endpoint for microscopic evaluation. RESULTS: The ED50 for 1,318-nm exposures to the rabbit cornea was determined to be 382 J/cm2, as measured at the 1/e2 (0.865 times that of the peak power per unit area). At each exposure site, there was a small (< 1 mm in diameter), white, circular, well demarcated corneal lesion characterized histologically by a band of stromal coagulative necrosis and endothelial necrosis, with sparing of the anterior epithelium. In addition, there appeared some potential for damage to Descemet's membrane at the highest energy level tested. CONCLUSIONS: Findings indicate that the rabbit corneais subject to injury at the 1,318-nm wavelength with the established ED50.