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Marta Stevanovic, Jasmina Cehajic Kapetanovic, Jasleen Kaur Jolly, Robert E MacLaren; Correlation of distinct fundus autofluorescence features with disruption of the overlying ellipsoid zone in choroideremia. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1856. doi: https://doi.org/.
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Choroideremia is an X-linked retinal disease that is driven by retinal pigment epithelium (RPE) loss, which leads to secondary degeneration of other retinal layers. In some choroideremia patients, the RPE adopts distinct phenotypes seen on fundus autofluorescence (FAF) – either a mottled appearance seen more peripherally or a smooth appearance around the fovea. Although retinal function is maintained over both areas, it is not yet known how these RPE changes predict the health of the overlying retina.
A retrospective review of anonymized FAF and optical coherence tomography (OCT) images (Heidelberg Spectralis, Heidelberg, Germany) from the left and right eyes of 20 choroideremia patients was performed. Only FAF images that contained the two distinct regions in both eyes, smooth and mottled, were included. Corresponding FAF and OCT images were then aligned and one horizontal trans-foveal OCT section was analyzed. The length of each smooth and mottled region was measured. Within each region, the percent covered by intact and disrupted ellipsoid zone (EZ) was determined. Intact EZ was defined as being homogenous with uniform thickness and no gaps or eruptions. 2-way ANOVA analysis was performed testing mottled versus smooth zones against percent intact versus disrupted EZ and in left and right eyes.
14 out of 20 patients had distinct smooth and mottled areas in both eyes and were included in the analysis. On average, 62.5±10.1% of the EZ in each smooth region of the right eyes was intact compared to 10.0±4.3% in the mottled areas. The same trend was observed in left eyes, where 76.5±7.2% of total EZ in the smooth regions was intact versus only 9.8±3.9% in the mottled areas (2-way ANOVA, p<0.0001). Hence the mottled FAF regions seen in choroideremia were associated with early EZ disruption far more so than the smooth areas.
The results of this study confirm that the RPE changes observed in choroideremia correlate with the health of the overlying photoreceptors. The smooth region of FAF is likely to represent early stages of choroideremia with most of the area containing preserved EZ, whereas the mottled zone indicates more advanced stages of the disease and has mostly disrupted EZ. Because of the clear relationship between FAF findings and EZ, FAF imaging can be used to identify areas of preserved EZ that could be rescued by gene therapy.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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