Progressive Neurodegeneration in Macular Telangiectasia Type 2 (MacTel)

Abstract

Purpose : MacTel has a complex pathogenesis that involves the retinal vasculature with a significant neurodegenerative component. In addition to outer retinal abnormalities (e.g. ellipsoid zone) that correlate with visual dysfunction, patients with MacTel have been shown to have retinal ganglion cell layer (GCL) and nerve fiber layer (NFL) thinning, but the rate of thinning of retinal layers is unclear. We sought to quantify the change in thickness over time of retinal layers in patients with non-proliferative MacTel.

Methods : This was an IRB-approved retrospective study of patients with MacTel presenting to the University of Iowa and Retina Consultants of Houston with at least two Heidelberg Spectralis SD-OCT scans separated by over 10 months. Exclusion criteria included: glaucoma, history of optic nerve disease, proliferative diabetic retinopathy, diabetic macular edema, choroidal neovascularization from any cause, vascular occlusion, prior plaque radiotherapy, anti-VEGF therapy, or advanced age-related macular degeneration. OCTs were segmented into 11 retinal layers using the Iowa Reference Algorithms (ver. 5.0.0). For each layer, mean thickness was computed for the 8 noncentral regions of the ETDRS grid. A mixed effects model was fit to each layer and region using lme4 for R (thickness ~ time + laterality + time:laterality + (1|subject)). Percent change was calculated as the rate of change / baseline thickness.

Results : 117 patients met criteria for this study; of these, 37 have been analyzed to date, with 81% female, median age 66 years old. Average NFL, GCL, and INL thickness decreased by 0.47%, 0.93%, and 2.1% per year in the parafoveal temporal region, respectively. Greatest percent loss was observed in the outer zone of the outer segments, with 7 of 8 regions having percent loss greater than 1.8% per year, and mean loss of 2.16% per year.

Conclusions : Patients with non-proliferative MacTel sustain progressive neurodegeneration that may exceed those with diabetes and no clinical retinopathy. Ongoing analyses will more definitively delineate the relationship between MacTel and neuroretinal thinning.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.