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Lauren M Renner, Emily Johnson, Kasie W. Paul, Travis B. Smith, Trevor J McGill, Martha Neuringer; In vivo quantification of macular RPE cell density in infant monkeys using fundus photography. Invest. Ophthalmol. Vis. Sci. 2016;57(12):233.
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© 2017 Association for Research in Vision and Ophthalmology.
The density of retinal pigment epithelial (RPE) cells in adult human and monkey eyes peaks in the fovea and decreases with eccentricity, as demonstrated by histology and by AOSLO autofluorescence, but has not been examined during development. Surprisingly, we have been able to visualize macular RPE cells in infant monkeys with standard fundus photography techniques, possibly as a result of the lack of RPE and choroidal pigmentation, and/or increased magnification due to small eye size. This study utilized this phenomenon to quantify the development of the RPE cell density profile longitudinally in infant monkeys in vivo.
RPE cells were visualized longitudinally in infant rhesus macaques (n=11) at 2, 4, 8, 16 and 24 weeks of age by color and red-free fundus photography and fluorescein angiography using a Zeiss FF450 fundus camera. For each animal and time point, the clearest central fundus image of any imaging modality showing visible RPE cells was selected. Images were analyzed with Mosaic Analytics Software (courtesy of Joseph Carroll) with manual correction. A custom MATLAB program was used to calculate RPE density in the 0.5 mm diameter foveal center and in three concentric annuli at 0.25-0.5, 0.5-0.75, and 0.75-1.00 mm eccentricities, with additional measurements at greater eccentricities when possible.
At 2 weeks of age, RPE cells were visible in the macula of all 11 infant monkeys. Density was highest in the central fovea (2,400 cells/mm2) and decreased progressively with eccentricity. By 8 weeks of age, RPE density increased in all regions; the increase was greatest in the central 0.5 mm, with density reaching 3,000 cells/mm2. The area in which RPE cells were visible decreased as pigmentation increased, and in some infants RPE cells were visible only in the central 0.5 mm of the fovea. By 16 weeks, RPE cells were no longer visible in most infants.
RPE cell density can be visualized and quantified in the infant primate macula using standard ophthalmic imaging techniques. Quantification of RPE cell density revealed the presence of a foveal peak as early as 2 weeks and a progressive density increase similar to the developmental pattern of foveal cone photoreceptor density.
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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