Imaging of optic disc drusen: Swept-Source (SS)-OCT versus B-scan ultrasound

Abstract

Purpose: Optic disc drusen are currently diagnosed by B-scan ultrasonography, but this modality is difficult to maneuver, uncomfortable to patients, and operator-dependent. The aim of this prospective study was to determine whether an alternative imaging technology, the Swept-Source (SS)-OCT, improves the ability to identify optic disc drusen compared to the gold standard of B-scan ultrasonography.

Methods: We recruited patients who were of 5 years of age or more and diagnosed with anomalous optic nerve heads. Subjects received a complete ophthalmologic exam of the anterior and posterior segments as well as a B-scan ultrasound and SS-OCT. The prototype SS-OCT system was operated at 1060nm wavelength with 100kHz axial scan rate. Images from each of the two imaging technologies were then independently and qualitatively assessed for the presence and visibility of drusen.

Results: A total of 13 patients (4 males and 9 females) were recruited. The average age was 47.6 years. Among these subjects, there were 21 eyes with optic disc drusen. Drusen were confirmed in B-scans by hyper-reflectance of the calcium deposits at low gain. In the SS-OCT, they were hypo-reflective bodies that could be visualized in a 3D cube, making it possible to also pinpoint their locations. Optic disc drusen were identifiable through SS-OCT in all 21 eyes (100%), had well-demarcated borders in 19 (90.5%), and were seen along their entire depths in 16 (76.2%).

Conclusions: While the B-scan tests for the hyper-reflective properties of the calcified bodies, the SS-OCT allows anatomic visualization of the actual deposits. Here, we were able to identify optic disc drusen in all of the eyes that were diagnosed with this condition through B-scan. The SS-OCT therefore has equal ability to detect drusen compared to B-scan ultrasonography, and the additional benefits of ease of conducting the exam, patient comfort, data standardization, and potential quantification of drusen size make it more clinically useful.