On the dark side of light: Genesis and prevention of two spectral types of retinal light damage

This thesis is on light damage to the retina. Photochemical light damage to the retina can even occur under ambient light conditions as demonstrated by Noell et al. (1966) They found green light (500 nm) the most powerful in causing retinal damage. Under higher irradiance conditions the action spectrum changes: Short wavelengths are then the most harmful (Ham et al., 1979; Ham, Mueller and Sliney, 1982; Gorgels and van Norren, 1995). With ever increasing irradiance the domain of thermal damage is entered. The highest retinal irradiance used in the experiments in this thesis is approximately 300 mW/ cm . This is a rather high 2 level, but insufficient to increase the retinal temperature over 10 C; the generally accepted safety o limit (Ham et al., 1979). Another argument against thermal damage, is the duration of the exposure. Thermal damage occurs in less then a second, or not at all (Ham et al., 1979; van Norren, Keunen and Vos, 1998). In the experiments in this thesis longer exposures (from 8 to 100 minutes) were required to cause damage. Thus, we have always dealt with photochemical rather than thermal mechanisms in retinal light damage as investigated in this thesis. The aims of the studies in this thesis were: (1) To document the development of two spectrally determined types of photochemical light damage. (2) To obtain more information about the mechanisms of these two spectral light damage types, and to evaluate possible protectors against retinal light damage