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Hilde Rogeberg Pedersen, Inger Christine Munch, Stuart James Gilson, Michael Larsen, Rigmor C Baraas; The effect of small hard drusen on local retinal structure in healthy adults. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5137. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate how small hard drusen affect local retinal structure in healthy adults by high-resolution in-vivo imaging of the retina.
Ninety-seven healthy males and females aged 19-36 yrs, with normal logMAR letter acuity and no observed ocular abnormalities, were included in the study. Color fundus photographs were obtained of the central 45 degrees in both eyes. Any bright element smaller than 63 µm in diameter whose shape, color, or proximity to adjacent abnormality indicated it was not hard exudate, was classified as a small, hard druse. Eyes with drusen were imaged with the Heidelberg Spectralis OCT and the Kongsberg Adaptive Optics Ophthalmoscope II (AO). Retinal layers were analyzed by calculating longitudinal reflectivity profiles (LRP). Cone density and mosaic regularity analysis was performed over and around drusen.
One or more small hard drusen were found within the central 20 degrees in 27 eyes in 21 of the 97 subjects, indicating a population prevalence of 21,6 % in this age group. The number of drusen per eye ranged from 1 to 8. Eight drusen per eye were found in one subject, all in a cluster. OCT revealed a granulated retinal pigment epithelium (RPE) complex in the area with multiple drusen. Discrete OCT-visible drusen (33 %) were moderately reflective and associated with localized internal thickening (4.11-7.52 µm) of the RPE complex or elevation of the RPE with slight displacement of the inner/outer segment (IS/OS) layer. One druse was located in Verhoeff's membrane (VM). The IS/OS layer and the external limiting membrane (ELM) were intact over all drusen, but ELM had reduced reflectivity above the drusen in two eyes. The RPE tended to be more reflective and prominent than VM above drusen. In AO images, drusen were hyperreflective circular or oval elements with blurred edges. The size of discrete drusen ranged from 20 to 56 µm. The cone density and regularity over drusen was not significantly abnormal. The VM druse was hyperreflective and surrounded by discontinuous hyporeflectivity.
In this study only one-third of small hard drusen were visible on OCT, all found within or under the RPE. All drusen were visible on AO showing an intact overlying photoreceptor mosaic with moderate alteration of the reflectivity of the adjacent components of the retina. The results may be relevant for the study of very early precursor stages of age-related macular degeneration.
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