Distribution and progression patterns of retinal low-reflective intraretinal spaces in Type 2 Idiopathic Macular Telangiectasia.

Abstract

Purpose : The presence of low-reflecting spaces in the inner and/or outer retina is a characteristic neurodegenerative sign in Type 2 MacTel. Their histological correlates, progression patterns or significance in the natural history of the disease are not well known. Our aim was to investigate the spatial characteristics of these spaces and their relationship with other features of the phenotype.

Methods : Optical Coherence Tomographic (OCT) volume scans centered on the fovea were acquired using Heidelberg Spectralis OCT devices at 11µm B-scan intervals (up to 261 B-scans/volume). Image volume data and multimodal fundus images were analyzed in FEI Amira v5.

Results : Thirty-seven eyes of 19 patients were analyzed; follow-up data were available for 18 eyes (mean follow-up 1.1 years). In early disease (no other OCT signs, 5 eyes), small convex spaces were seen at the boundaries of the outer plexiform layer (OPL), in the inner- and/or outer nuclear layers (INL/ONL) as well as the ganglion cell layer (GCL). These were scattered throughout or even outside the MacTel area. Within the GCL, planar or wedge-shaped spaces may be present near the foveal pit. In more advanced disease (vascular anomalies, hyperpigmentation, but no collapse, 12 eyes), larger spaces near the fovea appear on the OPL/ONL boundary with a tissue loss of Henle's layer in the ONL. Within the spaces, oblique strands with centrifugal ends pointing towards the ILM imply a schitic process in addition to tissue loss. The topographic distribution of cavities is often radial (22 eyes). Coincident with ONL spaces, cavities adjacent to the RPE may occur (27 eyes), and these tend to be paucifocal, bordered by an EZ break. At least initially, the external part of the ONL appears as a boundary between cavity systems, later the cavities may coalesce. Over time, in early disease, the volume of retinal spaces increases (mean±SD: 13%±11.8%/year, 9 eyes), whereas in late disease it tends to decrease due to outer retinal atrophy and a vertical restructuring of the retina (14.1% ±13.6% /year, 9 eyes).

Conclusions : Low-reflective retinal spaces may be early signs of MacTel, helpful in establishing a diagnosis. The morphology of ONL cavities may imply a disassociation and loss of fibers in Henle's layer. Depending on disease severity, an increase as well as a decrease in cavity volume may indicate a progression of the disease.

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