Dear Editor,

I enjoyed reading Paskowitz et al.'s (1) important summary of evidence indicating that in some specific types of retinal degeneration, light deprivation may prove to be of protective value. In respect of Stargardt Disease, they cite evidence from animal models that light deprivation can prevent A2E accumulation in the RPE, thus preventing the degeneration. A worthwhile point to note is that the destruction of A2E-laden RPE cells is light-induced, and the absorption spectrum of A2E peaks at 435 nm. Blue light is very much more effective in causing the death of A2E-containing RPE cells than green light (2).

It would thus appear that while total light deprivation may be effective in preventing A2E accumulation in RPE cells, protection specifically from blue light may slow down or prevent the death of RPE cells which already contain high levels of A2E. Filtering blue light is a strategy that is more practical to apply than total protection from light. Blue light may have an important role in driving the circadian cycle, as well as for psychological well being (3). Some caution may therefore be warranted in filtering out 100% of the blue light 100% of the time. Very substantial blue light protection can, however, be considered.

As the authors caution, clinical trials are required to confirm predictions arising from currently available evidence (1), but in addition to protection from light in general to the greatest extent practicable, protection specifically from blue light may be a strategy that proves to slow down the progress of Stargardt disease.

References

1. Paskowitz, D.M., LaVail, M.M. and Duncan, J.L. Light and inherited retinal degeneration. Br. J. Opthalmol. 2006;90:1060-1066.

2. Sparrow, J.R., Nakanishi, K. and Parish, C.A. The lipofuscin fluorophore A2E mediates blue light induced damage to retinal pigment epithelial cells. Invest. Ophthalmol. Vis. Sci. 2000;41:1981-1989.

3. Charman, W.M. Age, lens transmittance, and the possible effects of light on melatonin suppression. Ophthalm. Physiol. Opt. 2003;23:181-187.