Corneal thermal damage threshold dependence on the exposure duration for near-infrared laser radiation at 1319 nm

The corneal damage effects induced by 1319-nm transitional near-infrared laser have been investigated for years. However, the damage threshold dependence on exposure duration has not been revealed. The in vivo corneal damage thresholds (ED(50)s) were determined in New Zealand rabbits for 1319-nm laser radiation for exposure durations from 75 ms to 10 s. An additional corneal ED50 was determined at 1338 nm for a 5-ms exposure. The incident corneal irradiance diameter was fixed at 2 mm for all exposure conditions to avoid the influence of spot size on threshold. The ED(50)s given in terms of the corneal radiant exposure for exposure durations of 5 ms, 75 ms, 0.35 s, 2 s, and 10 s were 39.4, 51.5, 87.2, 156.3, and 311.1 J/cm(2), respectively. The 39.4 J/cm(2) was derived from the ED50 for 1338 nm (27.0 J/cm(2)). The ED(50)s for exposure durations of 75 ms to 10 s were correlated by a power law equation, ED50 = 128.9t(0.36) in J/cm(2), where t was the input in the unit of second, with correlation coefficient (R) of 0.997. Enough safe margins existed between the ED(50)s and the maximum permitted exposures from current laser safety standard. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)