Abstract
Purpose: :
To evaluate a novel ultra-widefield scanning laser ophthalmoscope (SLO) for fundus autofluorescence (FAF) imaging in patients with geographic atrophy (GA) secondary to age-related macular degeneration (AMD).
Methods: :
FAF imaging was performed with a prototype instrument for ultra-widefield imaging (exc. 532 nm; P200CAF, Optos Ltd, Scotland) and compared with a confocal SLO system (exc. 488 nm; Spectralis HRA, Heidelberg Engineering, Germany). A total of 78 eyes from 44 patients with (mean age 76 years, range 55-87) were examined. Images were evaluated for quality, FAF pattern analysis in the perilesional area, boundary delineation of atrophic areas and abnormal peripheral FAF intensities.
Results: :
While the P200CAF records a single image, several frames are averaged following automated alignment with the cSLO. In accordance with the cSLO FAF images, FAF signals were decreased in areas of GA allowing delineation of lesion boundaries. There was an overall similar appearance of perilesional abnormal FAF patterns. However, particularly for focal spots of increased FAF discrepancies were noted, which may relate to a lower signal-to-noise ratio with a single non-averaged P200CAF frame. Less absorption by macular pigment was seen in P200CAF images allowing accurate assessment of foveal involvement. Notable systematic differences in configuration and extension of uni- and multifocal atrophic patches were observed. Therefore, GA area quantification was not exactly comparable between the two systems. In 23 of 78 eyes (30%), peripheral changes beyond the 30x30 degree frame with increased or decreased FAF intensity were detected using the P200CAF.
Conclusions: :
The topographic distribution of FAF intensities in the central macula using the P200CAF ultra-widefield imaging system with green excitation wavelength is comparable to cSLO imaging. Detection of subtle FAF changes and GA area quantification may require further image enhancement. Visualization of peripheral retinal areas in a single frame allows for metabolic mapping of alterations beyond the posterior pole. This may be helpful for the assessment of the extension of retinal disease and more comprehensive phenotyping in future phenotype-genotype correlations.
Keywords: age-related macular degeneration • imaging/image analysis: clinical • retinal pigment epithelium