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William H. Merigan, Jennifer Strazzeri, David A. DiLoreto, Jr., William Fischer, Jennifer J. Hunter, Benjamin Masella, David R. Williams; Visual Recovery After Outer Retinal Damage in the Macaque. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3202.
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© ARVO (1962-2015); The Authors (2016-present)
Focal laser lesions of outer retina in a variety of animal models show rapid and substantial recovery which has been hypothesized to involve regeneration and/or migration of retinal pigment epithelium (RPE) cells and photoreceptors. This study examined in macaques, an animal model in which RPE cells and photoreceptors can be imaged in vivo, and thus tracked over time, the time course and magnitude of remodeling and functional recovery following severe damage to photoreceptors and RPE cells.
Using a Coherent Novus Omni laser, macaque retina was exposed to 647 nm laser light, 300 um diameter. These exposures resulted in funduscopically visible damaged focal regions. The time course of recovery was tracked with fluorescein angiography (FA), optical coherence tomography (OCT), and contrast sensitivity microperimetry. A map of contrast sensitivity was made in the region of the retina affected by the lesions by having trained macaques discriminate the orientation of minute patches of grating (gabor stimulus, σ = 0.15 deg).
OCT imaging showed initial damage to photoreceptors extending from the outer plexiform layer (OPL) to the retinal pigment epithelium (RPE). Severe disruption of RPE itself was indicated by FA leakage from the choroid over the first four days following the lesion, but there was no evident damage to inner retina. Visual loss in the first month extended beyond the funduscopically visible extent of the lesions, but by 2 to 3 months had recovered completely in some lesions and decreased to less than half the original area in others. Severely altered OCT signal near the inner-segment outer-segment (IS-OS) border remained evident in those lesions that showed residual visual loss.
Despite severe initial damage to RPE and photoreceptors by laser lesions, visual function recovered substantially over a period of more than one month. No evidence of damage was seen to inner retina, and the rapid visual recovery may reflect remodeling of outer retina through recovery, regeneration or migration of individual photoreceptor and RPE cells. Over this short time course, the precise nature of RPE cell and photoreceptor remodeling can now be tracked non-invasively with adaptive optics retinal imaging in individual animals.
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