Combining flood and multimodal scanning adaptive optics imaging in age-related macular degeneration

Abstract

Purpose : Adaptive optics (AO) imaging has improved our understanding of tissue changes during age-related macular degeneration (AMD), for instance through detailed observation of photoreceptor and retinal pigment epithelium (RPE) disruption and detection of novel features such as slowly migrating melanin-loaded cells (MLCs). However, flood and scanning-based AO systems show distinct features. Here, we compare flood and multimodal scanning AO imaging systems in patients with dry AMD.

Methods : Four patients with dry AMD were imaged during the same session with the rtx1 camera (Imagine Eyes, France) and the MAORI system (PSI, Boston) within an IRB-approved study. The rtx1 system provides AO-corrected full-field flood-illuminated imaging at 850nm over a 4° field. The MAORI provides AO-corrected confocal line scanning laser ophthalmoscopy (AOSLO) at 750nm over a 1° to 5° field, along with simultaneous coincident optical coherence tomography (AOOCT) at 840nm. The AOSLO channel contains both bright and dark field modes (also known as split detection or offset aperture).

Results : The contrast of atrophy margins in flood-illuminated images was often highlighted by lines of melanin deposits, while in bright field AOSLO the intact RPE layer provided a uniform dark background; in dark field AOSLO mode, margins were often demarcated by a hyperreflective border. In both modalities in atrophic areas the “pseudomosaic” (i.e. the mosaic of hyperreflective dots similar to the cone mosaic) was brighter than the true cone mosaic (i.e. over the intact RPE layer); the pseudomosaic was however better visualized with AOSLO. MLCs were consistently observed as hyporeflective clumps in flood AO, while they were not detected in AOSLO.

Conclusions : Parameters such as optical sectioning and distortion that differ between flood and scanning AO technologies affect AO imaging features of dry AMD. Atrophy margins, dispersed melanin and pseudomosaics showed differing contrast, resolution and visibility in flood AO, AOSLO bright and dark field. This highlights the importance of a multimodal approach in high resolution imaging in order to optimize interpretation and further understanding of the disease at the microscopic level.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Figure shows flood AO (left), bright (center) and dark field (right) scan AO images, and simultaneous coincident AO-OCT, with zooms: AM atrophy margin; CM cone mosaic; PM pseudomosaic; MLC melanin loaded cells.