Retinal injury thresholds for blue wavelength lasers

Abstract

Retinal injury thresholds in Rhesus monkey were experimentally determined for exposure to 441.6 nm HeCd laser irradiation. Exposure durations were 0.1, 1, 5, 16 and 100 s and 1/e retinal irradiance diameters were 50, 125 and 327 μm. Tissue response was observed via ophthalmoscope 1-hour and 48-hours post exposure. Thermal and/or non-thermal (photochemical) damage thresholds were obtained depending upon the exposure duration. The power of the HeCd laser was not sufficient to produce lesions observable at one hour or 48 horns for 1-second duration exposures at 441.6 nm when the retinal irradiance diameter was 327 μm. A threshold for this condition was estimated to be 26 mW total intraocular power based on data for longer duration exposures and smaller irradiance diameter exposures. These data were compared to data previously reported. While the data are in agreement for 100-second duration exposures, differences were noted for shorter exposures, most notably 1-second duration, 327-μm retinal irradiance diameter exposures at 441.6 nm. We obtained an estimated injury threshold that is about 16 times higher than that previously reported. The body of data collected in this study is shown to support the 1-s duration, 327-μm retinal irradiance diameter, 441.6 nm threshold estimated herein.Retinal injury thresholds in Rhesus monkey were experimentally determined for exposure to 441.6 nm HeCd laser irradiation. Exposure durations were 0.1, 1, 5, 16 and 100 s and 1/e retinal irradiance diameters were 50, 125 and 327 μm. Tissue response was observed via ophthalmoscope 1-hour and 48-hours post exposure. Thermal and/or non-thermal (photochemical) damage thresholds were obtained depending upon the exposure duration. The power of the HeCd laser was not sufficient to produce lesions observable at one hour or 48 horns for 1-second duration exposures at 441.6 nm when the retinal irradiance diameter was 327 μm. A threshold for this condition was estimated to be 26 mW total intraocular power based on data for longer duration exposures and smaller irradiance diameter exposures. These data were compared to data previously reported. While the data are in agreement for 100-second duration exposures, differences were noted for shorter exposures, most notably 1-second duration, 327-μm retinal irradiance diam...