Measurement and Reproducibility of Preserved Ellipsoid Zone Area and Preserved Autofluorescence Area in a Natural History Study of a Cohort of Eyes with Choroideremia

Abstract

Purpose : To define the reproducibility of optical coherence tomography (OCT) – defined ellipsoid zone (EZ) area and fundus autofluorescence (FAF) -derived preserved autofluorescence (PAF) area in eyes with choroideremia (CHM).

Methods : In this IRB-approved multicenter study, participants with a confirmed genetic diagnosis of CHM underwent spectral domain OCT and FAF imaging. Only eyes where either PAF or preserved EZ areas did not extend beyond the captured image area were included in this study. Certified Doheny Image Reading Center graders independently delineated boundaries of PAF on all FAF images utilizing the Heidelberg Spectralis Region Finder tool. The area of preserved EZ was quantified by two certified graders in a masked fashion by manual segmentation of the EZ band on all the individual b-scans of the 3-D volume, in order to generate a map of the preserved EZ. The results of the two independent gradings for both the FAF and OCT images were compared.

Results : A total of 148 eyes from 75 cases were included in the study. In 21% of eyes, the area of PAF had extended beyond the field of view of the FAF image. After excluding these eyes as well as ungradable low-quality images, a total of 114 FAF images were evaluated. The mean PAF area from the two independent gradings were 3.720 ± 3.340 and 3.692 ± 3.253 mm² respectively, with an Intraclass correlation coefficient (ICC) of 0.996. In 43% of eyes, the preserved EZ extended beyond the OCT field of view. After excluding these eyes as well as eyes with low quality ungradable OCT images, a total of 77 OCT images were evaluated. The mean preserved EZ area from the two independent gradings were 2.746 ± 2.319 and 2.858 ± 2.446 mm², respectively with an ICC of 0.991.
In the 77 eyes where both the preserved EZ and PAF were within the imaging field, the preserved areas were highly correlated (Pearson correlation coefficient = 0.98 p < .001), though the preserved EZ area was significantly larger than PAF area (2.81 ± 2.38 vs 2.71 ± 2.48 mm², paired t test p=0.03).

Conclusions : Quantification of both PAF and preserved EZ on FAF and OCT images, respectively, is highly reproducible in eyes with CHM. These variables may prove to be useful as anatomic outcome measures in clinical research and clinical trials for CHM.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.