Phototoxic action spectrum on a retinal pigment epithelium model of age-related macular degeneration exposed to sunlight normalized conditions.

Among the identified risk factors of age-related macular degeneration, sunlight is known to induce cumulative damage to the retina. A photosensitive derivative of the visual pigment, N-retinylidene-N-retinylethanolamine (A2E), may be involved in this phototoxicity. The high energy visible light between 380 nm and 500 nm (blue light) is incriminated. Our aim was to define the most toxic wavelengths in the blue-green range on an in vitro model of the disease. Primary cultures of porcine retinal pigment epithelium cells were incubated for 6 hours with different A2E concentrations and exposed for 18 hours to 10 nm illumination bands centered from 380 to 520 nm in 10 nm increments. Light irradiances were normalized with respect to the natural sunlight reaching the retina. Six hours after light exposure, cell viability, necrosis and apoptosis were assessed using the Apotox-Glo Triplex™ assay. Retinal pigment epithelium cells incubated with A2E displayed fluorescent bodies within the cytoplasm. Their absorption and emission spectra were similar to those of A2E. Exposure to 10 nm illumination bands induced a loss in cell viability with a dose dependence upon A2E concentrations. Irrespective of A2E concentration, the loss of cell viability was maximal for wavelengths from 415 to 455 nm. Cell viability decrease was correlated to an increase in cell apoptosis indicated by caspase-3/7 activities in the same spectral range. No light-elicited necrosis was measured as compared to control cells maintained in darkness. Our results defined the precise spectrum of light retinal toxicity in physiological irradiance conditions on an in vitro model of age-related macular degeneration. Surprisingly, a narrow bandwidth in blue light generated the greatest phototoxic risk to retinal pigment epithelium cells. This phototoxic spectrum may be advantageously valued in designing selective photoprotection ophthalmic filters, without disrupting essential visual and non-visual functions of the eye.

Suppression of melatonin secretion in healthy subjects with eyeglass LED delivery system.

OBJECTIVE: Practicability remains a problem in light therapy of biological rhythm disorders. We report here the effect on melatonin secretion of a device consisting of a prototype of eyeglasses including light emitting diodes (LED) in lenses (Somnavue). METHODS: Light (1,200 lx) was administered in a randomised crossover design to ten healthy subjects with Somnavue for 1 or 2 hours, Lumino (a helmet which administers light) for 1 hour, and placebo, beginning at 01:00 h. Plasma melatonin concentrations were evaluated between 20:00-05:00 h. RESULTS: Multiple comparisons showed differences between placebo and Somnavue administered for one or two hours (p<0.01 and p<0.05 respectively) and Lumino and placebo (p<0.05). CONCLUSIONS: In conclusion, Somnavue was able to suppress melatonin. The development of such a device could increase adherence with light treatment in SAD or circadian rhythm sleep disorders.