Photoreceptor disorder around subretinal drusenoid deposits and drusen revealed by adaptive optics scanning laser ophthalmoscopy

Abstract

 

Purpose

 

To describe the microscopic structure of photoreceptors impacted by extracellular lesions residing in the subretinal space and the sub-RPE (retinal pigment epithelium) space in patients with age-related macular degeneration (AMD), using multimodal imaging including a new-generation research adaptive optics scanning laser ophthalmoscope (AOSLO).

 

Methods

 

Twenty-nine patients (n=29) with early to intermediate AMD (grade 2-8 on the AREDS 9-step severity scale) were classified into 3 groups. Group 1 (9 eyes of 7 subjects) have subretinal drusenoid deposits (SDD) only in the macula, Group 2 (13 eyes of 7 subjects) have abundant (more than 20) densely packed small hard drusen (consistent with the clinic appearance of cuticular drusen, 50 - 75 μm diameter) only, and Group 3 (17 eyes of 15 subjects) have medium-large soft drusen (63 - 1000 μm diameter). These lesions were ascertained by presence in color fundus photographs, infrared reflectance, blue reflectance, autofluorescence images, and spectral domain optical coherence tomography (SD-OCT). SDD were classified with a 3-stage OCT-based grading system. The photoreceptor mosaic was assessed with AOSLO.

 

Results

 

AOSLO disclosed characteristic photoreceptor reflectivity perturbation over different lesion types. For SDD, photoreceptor reflectivity was reduced over stage 1 and stage 2 lesions with an indiscernible mosaic. For stage 3 SDD, AOSLO revealed a distinctive structure showing a hyporeflective annulus surrounding a core that is formed by the lesion material itself but bears a reflectivity superficially resembling photoreceptors (Fig.B1). Around the densely packed small hard drusen, the photoreceptor mosaic was largely visible and contiguous and with reduced, patchy reflectivity (Fig.B2). Around large soft drusen, the photoreceptor mosaic was invisible at the edge and visible on the top (Fig.B3). The en-face appearance of the photoreceptor mosaic was consistent with its cross-sectional structure as rendered by SD-OCT (Fig.C1-C3).

 

Conclusions

 

The dramatic photoreceptor reflectivity perturbation associated with SDD indicates that SDD may impose more direct and severe impact on overlying photoreceptors than drusen, suggesting that the retinal function in eyes with SDD may be more severely impired.  

 

Figure. AOSLO revealed characteristic photoreceptor reflectivity perturbation by different lesion types