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Valery V. Wittwer, Martin Niederhaeuser, Ghanem Ramzi, Sebastian Wolf, Ute E. Wolf-Schnurrbusch; Lesion Size Comparison of Geographic Atrophy in Blue Light vs. Green Light Autofluorescence Images. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4047.
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Conventional blue-light autofluorescence (AF) is well established in geographic atrophy (GA) studies. But the absorption of short wavelengths caused by the macular pigment (MP) leads to a dark spot overlying the fovea. The aim of our study was to compare image quality, AF patterns and size of GA patches in blue light (488 nm) and green light (514 nm) AF images.
Images from patients with GA secondary to dry ARMD were recorded with a modified cSLO (HRAmp, Heidelberg Engineering, Germany), which is optimized for AF imaging at an excitation wavelengths of 1=488 and 2=514 nm. The quality of all images was analyzed. Images assessed as either being of good or intermediate quality have been used for the evaluation of the AF patterns and the measurement of the total size of GA. For the size quantification the Region Finder software Version 1.0.16 (Heidelberg Engineering, Germany) was used.
In total 95 eyes of 95 patients (mean age 79±7 years, range 63-91 years) were included into the study. The image quality and the AF patterns grading was equal. Regarding the size measurement we found differences between the two wavelengths. The mean size of atrophic patches was significantly smaller (p ≤0.001) in images with 514nm excitation light wavelength (3.8±3.7mm2, 0.1-16.4mm2) compared to 488nm (4.4±3. 8mm2, range 0.4-16.1mm2). The delineation of GA was found to be challenging in the eyes with patches involving the central macula area and eyes with preserved fovea island. In these eyes we observed more difficulties in distinction of the central border of GA in images with 488nm because a dark spot was overlaying the fovea.
In our study the green light AF images obtained with 514 nm excitation wavelength are superior in an accurate analysis of small central pathologic changes and the determination of the size of central atrophic lesions. Central details were better visible because the AF signal is less absorbed by the MP.
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