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T. Duncker, J. P. Greenberg, S. H. Tsang, J. R. Sparrow, G. R. Barile, T. Smith, F. C. Delori; Absolute Autofluorescence (AbsAF) Measurements: Normal Subjects. Invest. Ophthalmol. Vis. Sci. 2010;51(13):262.
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Focal spectrophotometric measurements have shown that fundus AF increases with age¹. We measured two-dimensional AbsAF lipofuscin levels in vivo in normal subjects with a modified scanning laser ophthalmoscope (SLO).
Absolute AF measurement was done on 46 normal subjects (30 females, 16 males, 46 eyes) aged 4 to 57 yrs, with clear crystalline lenses using the HRA2 (Heidelberg Engineering Inc., Vista, CA) modified by insertion of a fluorescence reference chip in the retinal image plane. All images were obtained at the same sensitivity level in a single session after 15 seconds of bleaching. Correction was made for the internal reference, optical media density from normative data² and for refractive error. Median AbsAF values in the central 3000 micron region and in a temporal 1500 micron region were measured. Reproducibility was confirmed by analyzing 3 images taken directly after each other for 17 eyes and by repeat scanning on a different day.
Median central AbsAF and temporal AbsAF were highly correlated with age, ranging from 18 to 226 AbsAF Units centrally and 17 to 262 AbsAF Units temporally (Figure 1). Centrally, before correction, Gray Level (GL) = 50.17+2.37*AGE, p<0.0000 and AbsAF = 8.83+3.54*AGE, p<0.0000 after correction. Temporal AbsAF was always higher with AbsAF = 16.32+4.76*AGE, p<0.0000 (Figure 2). AbsAF measurements showed no significant difference between genders, ethnicities or iris color.
AbsAF measurements clearly demonstrate increasing physiologic lipofuscin accumulation throughout the central and temporal macula with increasing age. Normative data will be vital for future studies of retinal degenerative diseases.1. Delori FC et al, IOVS, 19952. Pokorny J et al, Appl. Opt., 1987
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