Quantitative Analysis of Retinal Structure Using Spectral-Domain Optical Coherence Tomography in RPGR-Associated Retinopathy

James J L Tee, Joseph Carroll, Andrew R Webster, Michel Michaelides, James J L Tee, Joseph Carroll, Andrew R Webster, Michel Michaelides

Abstract

Purpose: To quantify retinal structure and progression using spectral-domain optical coherence tomography (SDOCT) in patients with retinitis pigmentosa (RP) associated with retinitis pigmentosa GTPase regulator gene (RPGR) mutations.

Design: Retrospective observational case series.

Methods: Setting: Moorfields Eye Hospital, London, United Kingdom.

Subjects: Both eyes of 32 patients. SDOCT follow-up period of >1 year (3.1 ± 1.4 years).

Main outcome measures: Ellipsoid zone (EZ) width (EZW) and outer nuclear layer (ONL) and inner retinal layer (IRL) thickness measurements. Progression rates, interocular symmetry, and association with age and genotype were investigated.

Results: Significant differences were observed between baseline and final measurements of EZW and ONL thickness, but not for IRL thickness. Baseline and final EZWs were 2438 ± 1646 μm and 1901 ± 1423 μm for right eyes (P < .0001); 2420 ± 1758 μm and 1922 ± 1482 μm for left eyes (P < .0001). EZW constriction rates were 176.6 ± 130.1 μm/year and 173.1 ± 146.8 μm/year for right and left eyes. ONL thinning rates were 2.58 ± 2.85 μm/year and 2.52 ± 3.54 μm/year for right and left eyes. Interocular differences in EZW and ONL progression were not significant (P = .8609 and P = .6735, respectively). Strong correlations were found between EZW constriction rates of right and left eyes (rs = 0.627, P = .0002) and between EZW constriction and baseline EZW (rs = 0.714, P < .0001). There was moderate negative correlation between EZW constriction and age (rs = -0.532, P < .0001). Correlation between ONL thinning and age was not significant, as were differences between EZW and ONL progression rates with respect to genotype.

Conclusions: This study provides SDOCT progression rates for RPGR-associated RP. There is overall interocular symmetry with implications for future treatment trials where 1 eye could serve as a control.

Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Figures

Figure 1
Figure 1
Baseline (Top) and final (Bottom) optical coherence tomography (OCT) images of a patient with RPGR-associated retinopathy, taken with a 1.5-year interval. Ellipsoid zone width was 1615 μm at baseline and 1359 μm on final OCT. Nasal outer nuclear layer (ONL) thickness was 84 μm at baseline and 63 μm on final OCT. Nasal inner retinal layer (IRL) thickness was 105 μm at baseline and 119 μm on final OCT. Temporal ONL thickness was 74 μm at baseline and 51 μm on final OCT. Temporal IRL thickness was 131 μm at baseline and 143 μm on final OCT.
Figure 2
Figure 2
Flowchart documenting the recruitment of subjects with RPGR-associated retinopathy as per the inclusion and exclusion criteria.
Figure 3
Figure 3
Scatterplot of interocular ellipsoid zone width (EZW) at baseline for all study subjects with RPGR-associated retinopathy, right eyes corresponding to left eyes. Spearman correlation coefficient, rs = 0.931, P < .0001 indicates a very strong and significant interocular correlation.
Figure 4
Figure 4
Scatterplot of interocular ellipsoid zone width (EZW) constriction rates for all study subjects with RPGR-associated retinopathy, right eyes corresponding to left eyes. Spearman correlation coefficient, rs = 0.627, P = .0002 indicates a strong and significant interocular correlation in EZW progression.
Figure 5
Figure 5
Scatterplot of ellipsoid zone width (EZW) constriction rates vs EZW at baseline for study subjects with RPGR-associated retinopathy. There is a strong and significant correlation indicating greater progression rates in eyes with larger EZW (rs = 0.714, P < .0001).
https://www.ncbi.nlm.nih.gov/pmc/articles/instance/5451208/bin/figs1.jpg
Dr James J.L. Tee, MBBS, FRCOphth is a clinical research fellow with the University College London Institute of Ophthalmology and Moorfields Eye Hospital, London, United Kingdom. Dr James J.L. Tee graduated with a medical degree from Imperial College, London, United Kingdom in 2005 and completed his ophthalmology residency at Moorfields. He was admitted in 2013 as a fellow of the Royal College of Ophthalmologists, United Kingdom. His current research interests involve RPGR-associated retinitis pigmentosa and retinal imaging.

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