Imaging of remnant cone structure in outer retinal lesions in macular telangiectasia (MacTel) type 2

Abstract

Purpose : In some cases of MacTel, outer retinal lesions may recover spontaneously,[1] noted by recovery of ellipsoid zone (EZ) reflectivity on spectral domain optical coherence tomography (SDOCT).[2] As split-detection adaptive optics scanning light ophthalmoscopy (AOSLO) enables visualization of cone photoreceptor inner segments,[3] we investigated cone structure in EZ lesions on SDOCT by confocal and split-detection AOSLO.

Methods : Nine eyes of 6 subjects (53.5 ± 4.0 years, 2 women, 4 men) with MacTel type 2 underwent SDOCT (Heidelberg Spectralis) and AOSLO imaging. AOSLO images were montaged and aligned with infrared reflectance and en face SDOCT images using retinal vasculature. En face images were generated in Heidelberg Eye Explorer (version 1.9.10.0) by maximum intensity projection of segmented EZ (Fig B). En face images were used to guide AOSLO imaging and not for direct comparison of cone location due to large distances between B-scans. Images were compared to determine presence of cones within a lesion. Parafoveal cone density was measured using split-detection AOSLO images.

Results : Lesions (mean area ± SD, 0.39 ± 0.69 mm²) were identified as areas of absent EZ by SDOCT (Fig A). All 9 eyes contained remnant cone structures within or on borders of lesions visible by split-detection AOSLO (Fig C) but not visible by confocal AOSLO (Fig D). Cone density in foveal lesions was 32,298 cones/mm². The cone mosaic surrounding discrete lesions was relatively intact (44,799, 38,277, and 25,912 cones/mm² at 1, 2, and 3° eccentricity, respectively).

Conclusions : In MacTel, clusters of remnant cones may be present within outer retinal lesions, consistent with previous histological data.[4] Future work will use split-detection AOSLO to longitudinally monitor cones within and surrounding lesions and to aid in assessing the potential to restore cone function in MacTel. [1] Staurenghi PMID24755005 [2] Wang PMID25587056 [3] Scoles PMID24906859 [4] Powner PMID23769334.

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

 

Figure. Assessing cone structure within EZ lesions in MacTel. (A) SDOCT B-scan through fovea of a 56-year-old male. Yellow arrow, EZ lesion. (B) En face SDOCT image. Green line, level of B-scan in A. Green box, area shown in C-E. Aligned split-detection (C), confocal (D) AOSLO, and en face (E) images from the outlined area in (B). Green arrows, at level of B-scan in A, point to cluster of cones visible by split-detection AOSLO within the lesion.