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Thomas Ach, Nikolai Kleefeldt, Carla Pröbster, Ioana S Tarau, Katharina Bermond, Clara Reichel, Kenneth R Sloan; Quantified fundus autofluorescence (QAF) imaging – the use of age-related standard retinas and improved methods for analysis. Invest. Ophthalmol. Vis. Sci. 2019;60(11):PB0179.
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In vivo QAF uses an internal reference to compare retinal AF intensities between subjects and in follow-ups. For analysis, normally the mean QAF intensity (QAF8; PMID: 22016060) of a ring of certain width around the fovea is measured (PMID: 23860757, 26551331). The predefined area at a fixed location, however, limits precise analysis of subtle changes or lesions exceeding common QAF8 patterns. This study offers improved analysis patterns and provides standard retinas for each decade for detailed QAF analysis.
140 healthy subjects (5-77 years, clear lens) underwent multimodal imaging (color fundus, red free, infrared, AF (488,787nm), QAF (488nm) and SD-OCT using Spectralis and modified HRA2 (Heidelberg Engineering) and FF450 (Zeiss) cameras/devices. Custom FIJI plugins enabled: 1. Determination of the fovea and the edge of the optic disc in SD-OCT/infrared images. 2. Alignment and superimposition of multimodal images based on retinal vasculature. 3. Adjustment to age-related optical media density (for QAF). 4. Building of standard QAF retina maps for each decade and comparison of individual retinas to these standards. 5. To semi-automatically detect and edit retinal vasculature signals (if necessary for analysis). 6. Use of predefined grids (ETDRS; Delori pattern, modified grids) to manually draw regions of interest (free-hand tool) for detailed QAF analysis at specified regions.
For each decade, at least 9 subjects were multimodal imaged. All images were registered based on vasculature and then matched using the location of the fovea and the edge of the optic disc. QAF standard retina maps for each decade plot QAF intensities for each pixel at a certain distance and direction from the fovea. Modified, finer overlay grids (as commonly available) revealed that the hot spot of AF (temporal superior edge of the macula) slightly shifts with age. Free-hand tools enabled to accurately measure QAF values within sharply defined regions of interest.
A pre-requisite for accurate QAF analysis is age-corrected standard retinas which then can be used for comparison with diseased eyes. Furthermore, modified analysis patterns enable a more precise evaluation of selected areas or disease-related lesions re QAF changes (e.g., in age-related macular degeneration), currently examined in ongoing studies.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.
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