Characterizing macular edema in retinitis pigmentosa through a combined structural and microvascular optical coherence tomography investigation

Abstract

The aim of the study was to characterize macular edema (ME) in retinitis pigmentosa (RP) by means of quantitative optical coherence tomography (OCT)-based imaging. The study was designed as observational, prospective case series, with 1-year follow-up. All RP patients underwent complete ophthalmologic assessment, including structural OCT, OCT angiography, and microperimetry (MP). The primary outcome was the characterization through quantitative OCT-based imaging of RP eyes complicated by ME. A total of 68 RP patients' eyes (68 patients) and 68 eyes of 68 healthy controls were recruited. Mean BCVA was 0.14 ± 0.17 LogMAR at baseline and 0.18 ± 0.23 LogMAR at 1-year follow-up (p > 0.05). Thirty-four eyes (17 patients; 25%) showed ME, with a mean ME duration of 8 ± 2 months. Most of the eyes were characterized by recurrent ME. The ME was mainly localized in the inner nuclear layer in all eyes. LogMAR BCVA was similar in all RP eyes, whether with or without ME, although those with ME were associated with higher vessel density values, as well as thicker choroidal layers, than those without ME. In conclusion, the inner retina is closely involved in the pathogenesis of ME. The impairment of retinal-choroidal exchanges and Müller cell disruption might be a major pathogenic factor leading to the onset of ME in RP.

Figure 1

Quantitative analysis scheme. Starting from the original OCT and OCTA data, we obtained the thickness measurements of the choroidal layers by considering five fixed samplings, subfoveal, at 750 µm (right–left) and at 1500 µm (right–left) (upper left part of the scheme). Choroidal vascularity index was calculated after the segmentation and the binarization of the choroid (upper central part of the scheme). Moreover, we used the automatic ETDRS-9 sector grid measurements of retinal layers (upper right part of the scheme). With respect to OCTA, we obtained the enface reconstructions of vascular plexa (lower central part of the scheme). After the binarization of the images and the exclusion of the FAZ area, we calculated vessel density metric (lower left part of the scheme). In addition, choriocapillaris porosity was calculated after the careful detection of the choriocapillaris flow voids (highlighted in red) (lower right part of the scheme).

Figure 2

Macular edema localization in retinitis pigmentosa. The magnified image identifies each retinal layer and detects macular edema mainly localized in the inner nuclear layer.