Retinal pigment epithelial (RPE) cells are largely postmitotic. They continuously phagocytose the outer tips of the photoreceptor outer segments (POS). Over the life span of an individual, this activity results, although surprisingly slowly, in the intralysomal accumulation of lipofuscin, or age-pigment. Native lipofuscin shows orange-red autofluorescence when exposed to blue light. The loss of energy resulting from the conversion of excitatory blue light into emitted orange-red light may induce photo-oxidative reactions. We exposed neonatal rabbit RPE cells in culture to purified POS from cow eyes. The material were either native or peroxidized by irradiation with UV-light before being added to the RPE cultures. Lipofuscin accumulation was studied by transmission electron microscopy and measured by microfluorometric registration of its autofluorescence. Cells exposed to peroxidized POS accumulated much more lipofuscin than those exposed to native POS, indicating that peroxidized outer segements are not digestable by lysosomal enzymes. Furthermore, lipofuscin-loaded RPE cells were considerable more sensitive to visible blue light than unloaded control cells. The former ones showed lysosomal membrane destabilization with ensuing leakage of lytic enzymes and eventually cell death. We suggest that photo-oxidation of lysosomal membranes surrounding accumulated lipofuscin may be of importance for the development of age-related macular degeneration.

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changes in contact lenses in connection with radiation from welding arcs. Scand. j. work environ. & health 5 (1979) [271][272][273][274][275][276][277][278][279]. Because of reports of risks associated with the use of contact lenses during exposure to welding arcs, the temperature changes in soft contact lenses were recorded in connection with certain types of welding [manual metal arc (MMA) welding, tungsten inert-gas (TIG) welding, and metal inert-gas (MIG) welding], both with free-hanging lenses and lenses applied to the eyes of anesthetized rabbits. A great increase in temperature was noted, especially with MMA welding. At a distance of 0.4 m the temperature of a lens on a rabbit eye rose from about 35 to 50°C within 6 min, whereas the air temperature only increased from 23 to 30°C. The increase was the greatest at the beginning of the welding period. Most of the lenses completely dried out during the experiment, and there would seem to be a potential risk that the lens would adhere to the cornea. One safety glass screen (DIN 10 A) proved effective in preventing the rise in temperature in contact lenses during MMA welding. Even though it is impossible to direct the eyes at the arc for a prolonged period of time, the use of contact lenses in connection with at least certain types of welding is not to be recommended without the use of a suitable safety glass screen (or safety glasses). With regard to the large number of particles in the welding environment, also a risk factor for contact lens wearers, it is doubtful whether even safety glasses or screens are satisfactory unless they fit closely.

The transmittance and absorption properties of contact lenses. Scand. j. work environ. & health 5 (1979) 262-270. The transmittance and absorption properties of certain soft-lens materials with a low and a high water content and a hard-lens material were analyzed by a spectrophotometric technique over a broad spectrum from ultraviolet (195 nm) to far infrared (40,000 nm) radiation. The dry lens materials not only showed marked absorption within the shortwave region of ultraviolet, but also very strong absorption within the infrared range, especially medium and far infrared. Wet soft-lens material showed greatly increased absorption within the infrared regions in which water shows absorption maximums. Therefore the wet softlens materials absorbed nearly 100°/0 of the radiation within the greater part of the medium and far infrared ranges. Transmittance and absorption were inevitably affected by the thickness of the material, but differences between the various makes of lens were minor. It is clear that sources of high-energy radiation, particularly within the infrared spectra, may constitute hazards with regard to the absorption of radiation and the consequent generation of heat in contact lenses.