Solar retinopathy: its significance for the ageing eye and the younger pseudophakic patient.

The sun is the main source of ultraviolet (UV), visible and infrared radiation reaching our atmosphere. The short wavelength components of the sun's spectrum have been shown to have deleterious effects on the retinal photoreceptors. These effects are photochemical and mostly not thermal in nature. Except in early life, most of the ultraviolet (300-400 nm) is effectively filtered out by the lens which in later life also filters out considerable proportions of shorter visible wavelengths to 450 nm. The photochemical effects are mediated by the production of free radicals from the interaction of oxygen, photons and receptor molecules. These radicals attack, among others, polyunsaturated fatty acid components of cell membranes which may eventually degenerate. Protective mechanisms within the receptors and the adjacent pigment epithelium may be overwhelmed in the presence of high retinal irradiances over prolonged periods of time--as may occur in aphakic and pseudophakic eyes. The cone system, with a much slower replacement rate of light-sensitive membranes, is more likely to suffer permanent damage than the rod system, with predictable consequences. The above considerations have special relevance in old patients because of their age-compromised retinas, and in the younger patient who may be rendered aphakic or pseudophakic and faces a prolonged period of exposure to excessive UV irradiation as a consequence. Protection for the retina, whether by sunglasses or UV-absorbing intraocular lenses, as appropriate, is recommended.