Multi-platform imaging in ABCA4-Associated Disease

Lijuan Chen,Stephen H Tsang,Jose Ronaldo Lima De Carvalho,Stanley Chang,Winston Lee,Rando Allikmets,Janet R Sparrow

doi:10.1038/s41598-019-42772-z

Abstract

Fundus autofluorescence (FAF) imaging is crucial to the diagnosis and monitoring of recessive Stargardt disease (STGD1). In a retrospective cohort study of 34 patients, we compared FAF imaging platforms varying in field size (30° and 55°: blue/SW-AF and NIR-AF; 200°: ultrawide-field, UWF-AF), excitation wavelength (488 nm, blue/SW-AF; 532 nm, UWF-AF and 787 nm, NIR-AF) and image processing. Due to reduced absorption of 532 nm and 787 nm light by macular pigment, foveal sparing was more readily demonstrable by green/UWF-AF and NIR-AF imaging. Prominent in green/UWF-AF images is a central zone of relatively elevated AF that is continuous inferonasal with a demarcation line bordering lower AF nasally and higher AF temporally. This zone and border are more visible in STGD1 than in healthy eyes and more visible with green/UWF-AF. With the development of AF flecks, inferonasal retina is initially spared. Central atrophic areas were larger in NIR-AF images than in blue/SW-AF and green/UWF-AF images and the presence of a contiguous hyperAF ring varied with imaging modality. Flecks visible as hyperAF foci in blue/SW-AF images were also visible in green/UWF-AF but were often hypoAF in NIR-AF. Since disease in STGD1 often extends beyond the 30° and 55° fields, green/UWF-AF has advantages including for pediatric patients. The imaging platforms examined provided complementary information.

Highlights

Recessive Stargardt disease (STGD1) is the most common inherited form of juvenile macular degeneration and is caused by pathogenic variants in the ABCA4 gene[1]
In near-infrared AF (NIR-AF) images acquired from carriers of X-linked ocular albinism (GPR143/OA1), the fundus presents as a mosaicism in which patches of NIR-AF signal correspond to pigmented areas and alternate with patches of darkness[11]
Since green/UWF-AF is used in the clinic and the ease of imaging with the green/UWF-AF platform (Optos) has advantages including for patients presenting with early-onset disease such as STGD1, but there are no comparisons of blue/SW-AF, NIR-AF and green/UWF-AF images in the literature

Summary

Introduction

Recessive Stargardt disease (STGD1) is the most common inherited form of juvenile macular degeneration and is caused by pathogenic variants in the ABCA4 gene[1]. Fundus autofluorescence (AF) as a non-invasive imaging technique often enables the detection of abnormalities that are invisible by standard color fundus photography As such fundus AF is used for the diagnosis and monitoring of disease progression in STGD1. The maximum NIR-AF signal is observed in the center of the fundus and has a width of ~8°5–7 This signal is considered to be derived primarily from RPE melanin with a lesser contribution from choroidal melanocytes. This area of elevated NIR-AF corresponds to the area of high melanin optical density observed in color fundus photographs and with the area of reduced SW-AF that surrounds the area of strongest macular pigment absorption[5]. Since green/UWF-AF is used in the clinic and the ease of imaging with the green/UWF-AF platform (Optos) has advantages including for patients presenting with early-onset disease such as STGD1, but there are no comparisons of blue/SW-AF, NIR-AF and green/UWF-AF images in the literature

Methods

Results

Conclusion