En Face OCT Imaging as a Stand-Alone Modality for Monitoring Disease Progression in Intermediate AMD

Abstract

Purpose : En face optical coherence tomography (OCT) imaging was investigated as a stand-alone method for monitoring disease progression in eyes with intermediate age-related macular degeneration (iAMD).

Methods : A retrospective review of a prospective study consisting of subjects with iAMD was performed. All subjects underwent 6X6mm swept-source OCT (SS-OCT) imaging at their baseline and follow-up visits. En face images were generated using a slab with segmentation boundaries positioned 64 to 400 µm beneath Bruch’s membrane to identify persistent choroidal hypertransmission defects (hyperTDs), hyperpigmentation (hyperPig), and calcified drusen (CaD). On en face OCT imaging, hyperTDs were defined as bright areas having a greatest linear dimension ≥ 250 µm while hyperPig and CaD were defined as dark areas known as hypotransmission defects (hypoTDs). CaD progressing to atrophy would form donut lesions on the en face images, which are defined as a rim of hyperTD adjacent to a hypoTD core. The corresponding B-scans were used to confirm the different lesions after it was identified on the en face images. Drusen volume measurements were obtained with a validated SS-OCT algorithm.

Results : A total of 171 eyes from 121 patients with iAMD and only drusen at baseline were included. During the follow-up period, 48% of eyes developed at least one hyperTD, which included donut lesions. About 89% of these hyperTDs identified on the en face image developed within areas containing hypoTDs, which corresponded to hyperPig or CaD. Over time, these hyperTDs would gradually enlarge as new lesions developed. Eventually, individual hyperTDs would merge together and form larger areas of atrophy. Simultaneously, drusen volume typically increased and then decreased as hyperTDs appeared. However, a minority of eyes developing hyperTDs did not have a significant drusen burden, which suggest alternative pathways for hyperTD formation.

Conclusions : En face OCT imaging can serve as a stand-alone modality for the detection and monitoring of disease progression in iAMD. In addition, the same scan pattern can be used by different algorithms to identify the various lesions over time as well as drusen area and volume, outer retinal layer thickness, and choriocapillaris flow deficits.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.