Total Neuro-retinal Tubulation (TNT), a novel imaging finding

Abstract

A peculiar tubular structure was found in the left eye (LE) of a 71-year-old patient with diabetic retinopathy, who already had undergone panretinal-photocoagulation, detected by spectral-domain optical coherence tomography (SD-OCT) as an incidental finding. The reason for consultation was vitreous hemorrhage of the fellow-eye. Fundoscopic examination of LE revealed three oval retinal holes separated by small bridges of retinal tissue, which corresponded to tubular structures visible in SD-OCT, surrounded by photocoagulation scars. Optical coherence tomography B-scans of these structures revealed a tubular arrangement of tissue, composed of solid parts and hyporeflective cystoid spaces. Intermittent choroidal hypertransmission was detected deep to the tubular structures indicating impaired or absent retinal pigment epithelium (RPE). OCT-Angiography was performed using the Zeiss Plex Elite 9000 swept source device (Zeiss Meditec, Dublin, California, USA). Within the tubular structures, no flow signal was detected. Segmentation at the level of the outer retina choriocapillaris (ORCC) indicated partially intact choriocapillaris in the areas of tubular structures and retinal holes. We hypothesize that the tubular structures mainly consist of neuro-retinal tissue and propose the term total neuro-retinal tubulation (TNT). We postulate that the edge curling effect that leads to the tubular arrangement relates to focal retinal tears caused by tractional forces acting on the retina in this case by scarring in response to laser photocoagulation. Since the retinal periphery is more prone to retinal tears, widefield OCT imaging modalities are likely to offer further insights into this newly described finding and shed greater light on the biomechanical properties of the retina. Histopathological investigation is required to make a valid statement about the histology of TNT.