Comparison of Adaptive Optics Scanning Light Ophthalmoscopic Images to Structure and Function Within and on the Borders of Hyperautofluorescent Rings in Retinitis Pigmentosa

Abstract

Purpose: To compare images obtained with adaptive optics scanning light ophthalmoscopes (AOSLO) to measures of visual function and retinal structure within the hyperautofluorescent ring where they are relatively preserved, and on the ring border in patients with retinitis pigmentosa (RP).

Methods: A Canon prototype, AOSLO system 1 was previously used to obtain images from 15 eyes of 15 RP patients with visual acuities 20/20-20/30, and hyperautofluorescent rings (ARVO 2012). To aid in the interpretation of the photoreceptor mosaic, AO images were obtained in a subset of 5 patients along the horizontal meridian (fovea +/- 10 degrees) with Canon AOSLO prototype 2 and with a custom research AOSLO system.[1] In addition to AOSLO imaging, 10-2 visual fields (Carl Zeiss Meditec Inc.) and cone and rod mediated visual sensitivities were measured (Haag-Streit AG). Fundus autofluorescence and spectral domain-optical coherence tomography (OCT) line scans through the fovea were also obtained (Spectralis HRA+OCT Heidelberg Engineering GmbH). The thickness of the total receptor layer (R+: Bruch’s membrane to the border between the inner nuclear layer and outer plexiform layer) was measured using a computer-aided manual segmentation technique; values were compared to those for 30 age-similar normals.[2]

Results: Within the ring, the inner segment ellipsoid band (ISe) was preserved and cone mediated visual sensitivity ranged from 0 to -6dB of normal. The AOSLO images from both systems showed dark areas/patches where photoreceptors appeared to be absent, this included the foveal area imaged with the higher resolution system where OCT R+ layer thickness and cone sensitivities were normal for 3 patients. On and outside the ring border, the ISe was absent, the R+ layer was significantly decreased, and there was marked cone sensitivity loss (13-35dB); images from both systems showed regions with ambiguous cone structure. With the higher resolution system, their size and shape suggest the presence of RPE cells with patches of preserved photoreceptors.

Conclusions: Retinal imaging with AOSLO systems provides additional information about RP that is not apparent on OCT or visual function measures. 1. Sulai, Dubra. Biomed Opt Express. 2012, 3:1647-61. 2. Hood et al. IOVS 2009, 50:2328-36.

Keywords: 758 visual fields • 550 imaging/image analysis: clinical • 696 retinal degenerations: hereditary