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Elena Rodrigo Diaz, Humza Tahir, Jeremiah Michael Kelly, Neil Robert Alan Parry, Tariq Aslam, David Carden, Ian J Murray; Functional and structural progression in early AMD; dark adaptation best predicts morphology. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2661. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the morphological features of early AMD observed in colour fundus (CFP) and fundus autofluorescence (FAF) images with functional measures of visual acuity, contrast sensitivity (CS) and dark adaptation (DA).
A total of 65 subjects were recruited for the study. 52 were AMD patients (mean age 73 ± 12.98 years) and 13 age-matched controls (mean age 67.77 ± 9.72 years). A TRC50DX Non-Mydriatic Retinal Camera was used to obtain stereo fundus images and these participants were categorized according to the AREDS International Classification System for AMD. All AMD patients were within grades 2-3. FAF images were recorded with a sCLO Heidelberg Spectralis HRA+OCT and categorized according to Bindewald et al. (2005), IOVS. BCDVA was measured using an ETDRS chart. A Pelli-Robson chart was used to test CS as the number of letters read correctly. DA was measured psychophysically at 6° eccentricity in the superior retina using a PC-based technique described in Patryas et al. (2013), Graefes Arch Clin Exp Ophthalmol. Following a localized bleach, recovery of sensitivity was characterized with a 7 parameter model using purpose developed software written in Matlab. Thresholds were obtained using method of adjustment.Data were analysed with non-parametric statistics; Kruskal-Wallis rank test was used to test for differences and the significance of associations between structural and functional changes was determined using Spearman’s rank correlation coefficient
BCDVA did not differ between normal eyes and early AMD eyes, either for CFP (ρ=0.16, p=211) or FAF (ρ=0.28, p=0.024) classifications. CS showed an association with AMD severity according to CFP (ρ=0.38 p<0.002) and FAF (ρ=0.50, p<0.0001). The strongest correlations were found for the rod-mediated parameters of DA; rod recovery slope (S2) predicted both the CFP and the FAF classification closely (ρ=0.60, p<0.0001). Similar levels of association were found for the rod-rod break (β-point), CFP (ρ=0.61, p<0.0001) and FAF (ρ=0.55, p<0.0001).
As previously reported, BCDVA is a poor indicator of pathological status in early AMD. The rate of rod recovery (S2), is an accurate index of the severity of early AMD. It will help understand the morphological stages, aid early diagnosis and be ideal for assessing the effectivity of new therapies.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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