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M. Busuioc, R.T. Smith, J.K. Chan, J. Koniarek; The Border Zone of Geographic Atrophy as Imaged by Infrared and Autofluorescence . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3003.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To measure in an objective way increased autofluorescence (HyperAF) and increased infrared reflectance (HyperIR) in the 250µ border zone around geographic atrophy (GA) in stage 4 age–related macular degeneration (AMD), and to examine the relationship between HyperAF and HyperIR lesions. HyperAF in the border zone around GA has been shown subjectively by Holz to precede new GA, but quantitative data are lacking. IR can image subretinal structures (Elsner), but GA has not been studied in IR, hence the potential importance of these analyses. Methods: Confocal scanning laser ophthalmoscope (SLO) images of 10 patients with GA were obtained with the Heidelberg HRA in both AF and IR modes. We compared them to each other and to standard fundus photographs by using image registration. We defined hyperAF/IR lesions, respectively, as having gray levels 1.5 standard deviations above the median gray levels of the respective images of the border zone. We measured the areas of HyperAF/IR within GA border zones as percentages of zone area and compared their distributions. Results: The GA lesions on IR showed nearly exact superimposition with the AF GA lesions. All our IR images showed a distinctly dark hyporeflectant ring at the edge of the GA, and had hyperIR lesions in the border zone just beyond this dark ring (either a few focal lesions or a partial second ring). Some of these bright lesions appeared to be drusen and others had no photographic counterpart. HyperAF, found in all cases, had mean area in the border zone 9.34% ±2.66% and the mean HyperIR area was 7.96% ±2.67%. There was generally significant association (but not exact superimposition) of HyperIR and HyperAF in this zone. With respect to all hyperIR lesions, the proportion associated with HyperAF lesions was 100% in two cases, zero in one case, and on average 53% ±39%. Conclusions: We found IR hyperreflectant structures in the border zone of geographic atrophy, usually in association with hyperAF. This suggests the presence of sometimes clinically inapparent, IR–detectable, subretinal deposits in the border zone that may be significant. Quantification of hyperAF and hyperIR structures in the border zone of GA may allow better understanding of the GA disease process.
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