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David G Birch, Kirsten G Locke, Yuhui Qui, Jenny Holt, David Kim, Peter Francis; Annual change in ellipsoid zone (EZ) length in patients with choroideremia. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4476.
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Choroideremia is an x-linked recessive progressive retinal degeneration caused by null mutations in the CHM gene (Xq21). Here we use spectral domain optical coherence tomography (SD-OCT) to measure annual rates of change in parameters reflecting photoreceptor structural preservation.
Patients with choroideremia and confirmed CHM mutations were enrolled in a multicenter natural history study. Inclusion criteria included intermediate disease with ≥ 30° visual field diameter (III4e) and preserved EZ within the central 10°. We report 12 months of follow-up from 20 patients (median age=35 yrs) from a single site. SD-OCT was obtained with a Heidelberg Spectralis. Linear b-scans were obtained in four meridians and measured by an experienced grader. Multiple steered OCT scans were obtained when necessary to cover the EZ. Rate of change was derived from a Linear Mixed Effect model (random intercept and slope) with time, eye, and interaction of eye and time as independent variables.
All patients had preserved central vision (median letters OD=84; OS=83.5).Two eyes had edges of preserved EZ that extended beyond the area imaged. For the remaining 38 eyes, the annual change in EZ length for each meridian is shown in the Table. The decrease in EZ at 1 year was significant for all but the vertical meridian. Differences in rates between eyes were not significant for any parameter.
The irregular EZ area in choroideremia can be sampled by obtaining b-scans from four meridians. The majority of meridians show a significant decrease over one year.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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