Volume rendering of superficial optic disc drusen

Abstract

Optic disc drusen (ODD) are calcified deposits potentially caused by disturbances in axonal metabolism. The clinical course and visual impairment of ODD is usually mild; however, significant ocular morbidity may occur, such as visual field defects and retinal haemorrhages. Optic disc drusen may pose a diagnostic dilemma and differentiating these from other entities that can lead to similar compressive axonal distress is imperative. We present a novel technique for three-dimensional (3D) characterisation of superficial ODD based on 3D volume rendering of optical coherence tomography angiography (3DOCTA) scans. Optical coherence tomography (Cirrus™ HD-OCT Model 5000 with AngioPlex, Carl Zeiss Meditec, Inc., Dublin, USA) scans were obtained from the optic nerve head of a healthy 22-year-old female. Consequently, 3D structural OCT data and OCTA were analysed, enabling ODD segmentation and spatial characterization. Volumetric analysis of superficial ODD showed a maximal drusen horizontal diameter of 223 μm, maximal vertical diameter of 268 μm, surface area of 6617 μm2 and volume measurement of 12,875 μm3. The drusen were characterised by a connected network of multiple drusen islands instead of forming a dense mass. Multiple vascular channels with perforating vessels were found across the drusen. Three-dimensional volume rendering of OCTA scans provided new insight on the spatio-anatomical features of superficial ODD. The new features herein described, namely multilobulated drusen islands and intradrusen channels, may directly contribute to the pathogenic events leading to transient non-embolic visual loss and small vessel occlusion secondary to ODD.