In vivo Imaging of Photoreceptor Loss Associated with Dry Age-Related Macular Degeneration Using Adaptive Optics Scanning Laser Ophthalmoscopy

Abstract

 

Purpose:

 

This study was designed to examine each clinical stage of Dry AMD with an adaptive optics scanning laser ophthalmoscope (AO-SLO) to assess the AMD induced changes in the macular photoreceptors.

 

Methods:

 

A custom built AO-SLO imaging system was used to obtain reflectance images of the cone photoreceptor mosaic in twelve dry age-related macular degeneration patients. The SLO light source used was a superluminescent diode (SLD) centered at 830 nm with a bandwidth of 62 nm. The deformable element is a mirao™-52d (Imagine Eyes) with at 50 µm actuator stroke. Video sequences of a 2° x 2° (1024 x 1024 pixel) scan area were acquired at a rate of 12 frames per second. An automated registration algorithm was used to average multiple frames to improve the signal-to-noise ratio and generate composite mosaics throughout the macula. A multimodal clinical imaging system (Spectralis™, Heidelberg Engineering) was also used to obtain wide field images and SD-OCT cross-sections in each patient.

 

Results:

 

The superior lateral resolution (~2 µm) of the AO-SLO system provided a highly detailed view of the macular photoreceptors which complimented the clinical imaging techniques. We were able to correlate photoreceptor disruption in the adaptive optics images with the SD-OCT cross-sections and wide field fundus photography. In early dry AMD, photoreceptor disruption was visualized using AO-SLO prior clinically observed changes in the patient’s central visual field or reduction in visual acuity. In late stage dry AMD, photoreceptor loss was observed in the immediate vicinity of geographic atrophy and larger, coalescent drusen. Image processing tools were developed to quantify reduction in photoreceptor density along the boundaries of atrophic lesions to monitor progressive degeneration.

 

Conclusions:

 

This study demonstrates the capabilities of adaptive optics retinal imaging to provide complimentary diagnostic findings in early stage dry age-related macular degeneration and monitoring the loss of photoreceptor cells as a function of disease stage. Additionally, this imaging technique may provide insight into the effectiveness and optimization of emerging therapies used to preserve vision in patient affected by AMD.

 

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