Investigators at the University of Rochester and Columbia University will characterize a recently discovered retinal change following light exposures across the visible spectrum. This change is an immediate reduction in the intensity of RPE autofluorescence (AF dimming) that, when the light exposure is intense enough, is followed by the disruption of the RPE and cone mosaics. Previously-published work from Rochester, using a new method for assessing light damage in vivo at a cellular spatial scale, has established that both AF dimming and RPE disruption occur at light exposures that are well below the maximum permissible exposure specified by the ANSI standard for the safe use of lasers, calling for a revision of the standard. The experiments proposed here will provide in vivo measurements of the threshold for AF dimming, RPE mosaic disruption, and cone mosaic disruption in macaque monkey retina as a function of wavelength. These experiments will be conducted in consultation with David Sliney PhD of the ANSI committee. Thresholds for these retina changes will be established by direct observation of the RPE and cone mosaics in the living monkey eye made with a novel fluorescence adaptive optics scanning laser ophthalmoscope at Rochester. These measurements will be supplemented with conventional methods such as fundus photography, fluorescein angiography, high-resolution OCT, and histology. A goal of the proposal will be to uncover the mechanism responsible for AF dimming, which can occur with relatively dim light exposures (>2J/cm^2). This phenomenon could be benign but could also signal a potentially damaging phototoxic effect caused by photooxidation of lipfuscin. Complementing the in vivo experiments on monkey will be in vitro experiments on cultured RPE cells, supervised by Janet Sparrow of Columbia University, to determine whether light exposures that cause AF dimming also cause photooxidation and phototoxicity. Elucidating the causes of light-induced phototoxicity may ultimately yield new ways to reduce the cumulative damaging effects of light exposure, and could eventually help protect the retina against other forms of insult such as macular degeneration.
This project will use a new high resolution imaging method to explore retinal damage caused by exposure to lights that are much dimmer than those previously thought to be safe. The results of this study will produce recommendations for revising the internationally-accepted standards for light safety. They may also result in methods that can eventually be exploited to protect the retina from light damage as well as other insults such as macular degeneration.
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