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Ethan bensinger, Yiyi Wang, Sowmya Ravikumar, Brian Patrick Schmidt, Austin Roorda; Survey of transient hyporeflective clusters of cones in healthy eyes. Invest. Ophthalmol. Vis. Sci. 2018;59(9):648. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
When imaging healthy eyes in the Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO) we frequently observed small patches of hyporeflective cones in the foveal region. Here we present results from a retrospective study to characterize the properties and prevalence of these anomalies.
AOSLO images - originally collected for other purposes – of subjects with no known ocular pathology were reviewed. The survey included all images collected within a radius of 1.5 degrees from the fovea, though not all subjects had images that spanned that entire field. The images were collected using either 680 nm or 840 nm light. Hyporeflective clusters comprising as few as three cones were reported. Whenever possible, images of the same region taken on different days were compared. Time spans between images ranged from 3 weeks to 1 year. Whenever obvious hyporeflective regions were identified, the size was measured by fitting an ellipse to the hyporeflective region and computing the area.
Images from 16 out of 64 eyes reviewed contained one or more hyporeflective cone clusters. 5 of the 19 clusters contained no identifiable photoreceptors while the other 14 clusters showed significantly reduced reflectivity over the area. The largest cluster of hyporeflective cones was 41 arcmin2 in area, but they were generally much smaller, having an average size of 16.03 arcmin2. Of the 6 eyes with follow-up images, all showed a decreased area at the second time point, though only 2 of those showed completely normal photoreceptor reflections over the entire area upon follow up. In 3 of the 6 cases, a new cluster of hyporeflective cones appeared.
Clusters of hyporeflective cones frequently appear in the foveal region of subjects with no known ocular pathology. The cause of the hyporeflectivity is not known but they tend to resolve over time, while new clusters may spontaneously appear in other retinal locations. The size is generally quite small, on the order of retinal pigment epithelium cells, which have areas spanning 6.2-9.2 arcmin2 arcminutes or 135-200 microns2. It is possible that some of these regions contain dysflective cones (cones that lose reflective properties but still retain measurable function), but the function of cones in these hyporeflective clusters has yet to be determined.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Images of clustered hyporeflective cones. Scale bar is 0.1 degrees.
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