Abstract
Purpose:
To compare short-wavelength autofluorescence (SW-AF) and near-infrared autofluorescence (NIR-AF) images in a cohort of patients with the clinical diagnosis of Stargardt’s disease (STGD1).
Methods:
22 patients with a mean age of 36 years (range: 9-78 years) were studied. Genotyping of the ABCA4 gene was performed in all patients using the ABCR 700 microarray and direct sequencing. SW-AF (488nm) and NIR-AF (787nm) images were acquired with the Spectralis HRA+OCT confocal scanning laser ophthalmoscope (cSLO) and the HRA2 cSLO (Heidelberg Engineering, Heidelberg, Germany), respectively. Images were registered with i2kRetina software (DualAlign LLC, Clifton Park, NY).
Results:
Although the disease-related autofluorescence patterns observed in SW-AF and NIR-AF exhibited many similarities, several distinct differences were observed. Areas of central atrophy were marked by severely decreased/absent SW-AF and were in some cases circumscribed by a ring of high intensity SW-AF. Conversely, atrophic areas were larger in NIR-AF images and bright rings in SW-AF corresponded to areas of reduced AF in the NIR-AF image. Foveal sparing within an area of central atrophy is difficult to detect by SW-AF due to macular pigment absorbance; however by NIR-AF preserved fovea emits brightness. Flecks in SW-AF images were often bright and sometimes were surrounded by a dark halo; conversely, in NIR-AF images flecks were occasionally bright but most often were uniformly dark or dark with a bright center. In healthy eyes, fundus SW-AF images often exhibit, inferior to the optic disc, a near-vertical discontinuity in AF intensity, with lower AF on the nasal side. This demarcation line may indicate the location of the embryonic optic fissure (Duncker et al. IOVS 53:6682, 2012). In healthy eyes, this boundary is not visible in NIR-AF images; however it is detectable in NIR-AF images obtained from patients with ABCA4 mutations.
Conclusions:
Melanin autofluorescence, captured through NIR-AF imaging of STGD1 patients, aids in the assessment of preserved retina and foveal sparing. NIR-AF may reveal disease progression in advance of SW-AF. The observation made concerning the NIR-AF signal at the optic fissure may indicate that the NIR-AF signal is modulated by the presence of lipofuscin. SW-AF and NIR-AF imaging each provide unique perspectives on fundus changes in STGD1 and can be used as complementary tools.
Keywords: 550 imaging/image analysis: clinical •
696 retinal degenerations: hereditary •
701 retinal pigment epithelium