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Alison L Huckenpahler, Emily J Patterson, Alexander E Salmon, Katie M Litts, Rebecca Mastey, Erica Woertz, Jenna Cava, Joseph Carroll; Examining the relationship between cone density and ellipsoid zone reflectivity. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2196. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Reflectivity of the ellipsoid zone (EZ) in OCT images is altered in several retinal diseases. Photoreceptors are thought to contribute to the EZ, so EZ integrity or reflectivity is a candidate biomarker of photoreceptor health. Here we examine the relationship between cone density (as assessed with AOSLO) and EZ reflectivity.
We imaged 22 individuals (7 subjects with achromatopsia (ACHM), 5 carriers of blue cone monochromacy (BCM), and 10 subjects with no ocular pathology) using Bioptigen OCT and a custom-built AOSLO (using confocal and non-confocal modalities). Axial length was measured and used to scale the images, which were then manually aligned using blood vessel patterns. For each subject, we estimated cone density in the AOSLO images within 115 x 115 µm regions of interest (ROIs) at 1° intervals from 3° to 7° temporal eccentricity. Peak intensity of the EZ band was measured on the OCT B-scan at matched retinal locations. EZ intensity at a given location was normalized to the average intensity of the retina (from the RNFL/GCL boundary to the RPE) at that same location.a
Consistent with previous studies,a patients with ACHM had lower EZ reflectivity than BCM carriers and subjects with no pathology (p<0.0001, Mann-Whitney), though the average retinal intensity did not differ between the diseased and non-diseased groups (p=0.2301, Mann-Whitney). Cone density varied from 907 to 34,027 cones/mm2 across the ROIs analyzed, though cones in the ACHM subjects had diminished waveguiding on confocal AOSLO. There was a weak but significant correlation between cone density and EZ reflectivity in BCM carriers and subjects with no pathology (R2=0.40, p<0.0001). In contrast, there was no relationship between cone density and EZ reflectivity in subjects with ACHM (p=0.1438).
Our findings in BCM carriers and subjects with no pathology are consistent with previous studies showing a relationship between EZ reflectivity and cone density.b However, the lack of a similar relationship in the ACHM subjects (whose cones have diminished waveguiding on AOSLO) suggests that EZ reflectivity may not be a good predictor of remnant cone structure. This may also be relevant to other retinal diseases in which cone waveguiding is altered. Further comparisons of EZ reflectivity and photoreceptor density/numerosity are needed across a wider range of retinal diseases.aPMID:22110066bPMID:28791546
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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