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Jie Zhang, Ranjani Sabarinathan, Tracy Bubel, David R Williams, Jennifer J Hunter; Spectral dependence of light exposure on retinal pigment epithelium (RPE) disruption in living primate retina. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2220. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Fluorescence adaptive optics scanning light ophthalmoscope (FAOSLO) retinal imaging provides a sensitive in vivo measure of light damage at a cellular level. Using FAOSLO, Morgan and Hunter et al have observed RPE disruption at light levels with light exposures below or close to the ANSI photochemical maximum permissible exposure (MPE). However, these findings were limited to two wavelengths. We extend the measurements across the visible spectrum.
The threshold retinal radiant exposure (RRE) for RPE disruption was determined at 460, 476, 488, 530, 543, 568, 594 and 671 nm. The retinas of four anaesthetized macaques were imaged with a 2 deg field immediately before and after and at 2 week intervals for at least 4 weeks following exposure below thermal MPE to a uniform 0.5 deg field. At each wavelength, multiple RREs were tested with 4 repetitions each to determine the threshold for photochemical RPE disruption. RPE disruption was defined as any detectable change from the pre exposure condition in the exposed region relative to the surrounding area. Photochemical MPE threshold was determined based on the RPE disruption 28 days after the exposure.
The visible light action spectrum dependence for photochemical RPE disruption has a shallower slope than the current ANSI photochemical MPE. At all wavelengths beyond 530 nm, the damage threshold is below the ANSI MPE. At 594 nm, light damage was observed at intensities 5 times less than the MPE.
We measured the action spectrum dependence for photochemical RPE damage across the visible light spectrum with the FAOSLO. Our data agree with a large literature showing that blue light is more hazardous than long wavelength light. However, using this in vivo measure of phototoxicity provided by FAOSLO, we find that thresholds are slightly lower than previously thought. The wavelength dependence in our data agrees most closely with the shallowest curves in the literature. It is considerably shallower than the spectral dependence of the ANSI MPE, emphasizing the need for more caution with increasing wavelength than previously thought.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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