The action spectrum of photochemical damage to the retina: A review of monochromatic threshold data

Abstract

Photochemical damage to the retina occurs for prolonged exposures of intense light. Two action spectra exist for this phenomenon. In rat an action spectrum matching the absorption spectrum of rhodopsin was found. In macaque, the susceptibility for photochemical damage decreased continuously from the UV to long visible wavelengths. Later, such a spectrum was also found in rat. In search for critical parameters that determine the shape of the spectrum we gathered all available data on the damage threshold dose for monochromatic radiation and noted the experimental conditions. The rhodopsin action spectrum was found in two sources; the other 16 sources adhered to the short wavelength spectrum. Comparing the conditions we conclude that the critical parameters for the generation of either action spectrum remain elusive. Experiments are suggested to resolve this issue and fill a few gaps in our knowledge. In 1966 Noell published his landmark study on photochemical damage of the retina. The action spectrum (in rat) was identical to the absorption spectrum of rhodopsin. Ten years later Ham published a different action spectrum (in monkey) with highest susceptibility in the blue rather than the green. This spectrum was later also found in rat. In an attempt to find the unique conditions for each spectrum we gathered all monochromatic threshold data from the literature. Two sources adhered to the Noell type, 16 to the Ham type. An analysis of the conditions did not yield unique ones. © 2011 The American Society of Photobiology.