Effect of body temperature on threshold for retinal light damage.

Body temperature is known to influence the threshold for retinal light damage, but the magnitude of the effect has varied substantially between previous studies. The purpose of the present study was to establish a quantitative relation between body temperature in the range of 30-42 degrees C and dose of radiation for a just visible change in fundo. Anesthetized pigmented rats were exposed to 380 nm radiation for 10 min. Four intensities were simultaneously presented. Funduscopic changes were noted 2-3 d after exposure. At 30 degrees C, threshold dose was 6 J/cm2; at 42 degrees C, it was about 1 J/cm2. A fair fit to the data could be obtained with a linear regression between log threshold dose and temperature. The slope was -0.067. In an additional experiment, threshold dose at 500 nm and 41 degrees C body temperature was established at 400 J/cm2. These results agree with data in monkey and rabbit, but they vary from earlier data in rats that show a slope of -0.8. Exposure time, damage criterion, and the chromophores involved in retinal light damage are possible factors in the discrepancy.