Impact of subretinal drusenoid deposits on surrounding photoreceptors in close proximity

Abstract

 

Purpose

 

To investigate the impact of subretinal drusenoid deposits (SDD) on surrounding photoreceptors in close proximity to the lesion with adaptive optics scanning laser ophthalmoscopy (AOSLO) and directional optical coherence tomography (D-OCT).

 

Methods

 

4 subjects diagnosed with age-related macular degeneration (AMD) and SDD were enrolled. AOSLO was performed to image the macula over a 20 x 20 degree area. D-OCT of solitary SDD identified by AOSLO was acquired using spectral domain OCT (Hiedelberg Engineering, Germany). High density volume scans over the SDD were obtained with the light entering the pupil at 3 points (center, left and right). The reflectivity of the ellipsoidal zone (EZ), the retinal pigment epithelium and SDD was examined at 23 SDD from 4 eyes and the dependencies with the incident angle of the light were assessed with linear regression.

 

Results

 

AOSLO revealed a distinct structure in stage 3 SDD, showing a dark annulus with indistinct photoreceptors surrounding a reflective core. D-OCT shows a dark gap in the EZ band on either side of the SDD. The gap width varies with respect to the direction of the incident light with an opposite dependency on each side of the lesion (p < 0.05 in both cases). The SDD was found to have no directional dependent reflectivity.

 

Conclusions

 

D-OCT indicates that the dark annulus seen by AOSLO consists of deflected or otherwise degenerated photoreceptors. From the variation of the gap size with differing incident angles it can be inferred that the preserved photoreceptors in the dark zone of an SDD are orientated toward the peak of the lesion. The results are consistent with histology describing SDD as solid, space filling lesions.

 

 

AOSLO image (a) and D-OCT (b-d) of the same SDD. Taken from a 79 year old female (white, non-Hispanic) with BCVA 20/25 and AREDS grade 7. Photorecptors can be seen in the AOSLO image outside the darker annulus surrounding the SDD. The green arrow in the AOSLO image shows the location of the D-OCT. The yellow arrows indicate the direction of the incident light in the B-scans. The green markers indicate the gap between EZ and SDD which corresponds to the dark annulus in the AOSLO image. The scale bars are 50 µm long.

 

Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 648 photoreceptors • 412 age-related macular degeneration