Longitudinal evaluation of optical coherence tomography and color fundus photography over 2 year follow up in patients with RLBP1 retinitis pigmentosa

Abstract

Purpose : Retinal thinning is a common feature of retinitis pigmentosa including patients with RLBP1 mutations (RLBP1 RP). Some RLBP1 RP patients also have white dots in the retina. A Natural History Study was initiated to evaluate functional and structural endpoints in RLBP1 RP patients. Here, we report preliminary 2-year results of optical coherence tomography (OCT) and color fundus photography (CFP) including OCT sublayer analysis (other endpoints in additional abstracts).

Methods : In a non-interventional, two-center, prospective study, 45 patients with RLBP1 RP were followed every 6 months, with OCT (3D-OCT 2000, Topcon & Cirrus, Zeiss) and CFP (3D-OCT 2000, Topcon). Total retinal thickness was reported for each of the nine ETDRS subfields. All scans were processed using single retinal layer analysis (OCTExplorer, IDx) for the following layers of interest: Ellipsoid Zone (EZ), Outer Nuclear Layer (ONL), total photoreceptors (PR) and Inner Retina (IR). Two trained graders evaluated OCT and CFP for retinal abnormalities. Annual progression and test-retest variability were calculated as change from baseline and intra-class correlation coefficients (ICC), respectively.

Results : OCT data were obtained from 43 RLBP1 RP patients over 2 years.. The baseline central retinal thickness (CRT) was 173 and 163 µm, with test-retest variability measured by ICC of 0.83 and 0.98 and annual progression slope of -0.002 and -0.004 for the right (OD) and left eye (OS), respectively. The retinal thickness in the other eight ETDRS subfields did not show significant changes. Preliminary results of OCT sublayer thickness analysis are displayed in the table. Epiretinal membrane (mostly peripheral) was observed in 86.7% and 80.0% at baseline, and 86.7% and 86.7% at 2 years in OD and OS eyes, respectively. Cystoid macular edema was observed in 4.4% and 6.7% at baseline, and 2.2% and 4.4% at 2 years in OD and OS eyes, respectively. Macular traction, macular holes and retinal cysts were also observed in some patients. Common features in CFP were: slight optic disc pallor, white dots or dark pigment, mild macular atrophy and slight narrowing of blood vessels.

Conclusions : RLBP1 RP patients showed reduced central and sublayer retinal thickness. There were no significant changes in retinal thickness over 2 years. CFP showed consistent features with the disease phenotype.

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