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Swetha Bindu Velaga, Amir H Hariri, Muneeswar Gupta Nittala, Aniz Girach, Kiran Vupparaboina, Jay Chhablani, Srinivas R. Sadda; Relationship between Choroidal Structural Parameters and Photoreceptor Layer Area in Choroideremia. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1513.
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© ARVO (1962-2015); The Authors (2016-present)
Choroideremia (CHM) is an X-linked recessive disease featuring progressive, degeneration of the neurosensory retina, retinal pigment epithelium (RPE), and choroid. The purpose of this analysis was to better understand the relationship between loss of the photoreceptors and alterations in the choroid in this disorder.
In this Institutional Review Board approved prospective cross-sectional study, 45 eyes of 45 subjects with CHM were included. Spectral domain optical coherence tomography (SD-OCT; Spectralis HRA+OCT) volume scan (using macular cube protocol of 1024 A-scans X 97 B-scans over a 6 mm X 6 mm area centered on the foveal center with ART = 14) images were collected to assess ellipsoid zone (EZ) area and choroidal structural parameters. After manual segmentation of the EZ and the inner and outer borders of the choroid in each B-scan of macular volume using reading center OCT grading software (OCTOR), EZ area, choroidal thickness (CT), choroidal volume (CV), and normalized choroidal intensity (CI) were computed. To calculate the choroidal vascularity index (CVI), a previously-reported binarization technique was used to segment the choroid into luminal and stromal areas. CVI (%) can then be computed as a ratio of luminal area to total choroid area. EZ area was correlated with these various choroidal parameters using linear regression analysis.
The mean EZ area was 4.16 ± 1.91 mm2, the mean CT was 89 ± 38 µm, the mean CV was 2.49 ± 1.07 mm3, and the mean CVI was 69.25 ± 9%. In univariate analysis, EZ area was significantly correlated with CT (r = 0.75, p < 0.001) and CV (r = 0.73; p <0.001), but not significantly correlated with normalized CI (r = -0.24; p = 0.31) or CVI (r = -0.17; p = 0.55). On multivariate analysis, EZ area was significantly and independently correlated with CV (r = 0.74; p = 0.002).
The preserved area of the ellipsoid zone in eyes with choroideremia is correlated with choroidal volume, confirming that the choroidal and photoreceptor degeneration are closely coupled. Intrinsic alterations within the choroid (reflected by the CI and CVI), however, did not impact the area of photoreceptor preservation.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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