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Quantitative Autofluorescence Measurements
Author(s) -
SMITH RT,
GREENBERG J,
DELORI F
Publication year - 2011
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2011.3314.x
Subject(s) - autofluorescence , reproducibility , magnification , ophthalmology , optics , retinitis pigmentosa , refractive error , medicine , materials science , retinal , fluorescence , chemistry , physics , eye disease , chromatography
Purpose Technology for quantitative measurement of fundus autofluorescence (AF). Methods Scanning laser ophthalmoscopes (SLO’s, HRA2 and Spectralis, Heidelberg Eng.) were modified by insertion of an internal AF reference to account for variable laser power and detector sensitivity. 30° images (mean of 9 without histogram stretching) were acquired from normal test subjects (10‐60 y/o) after a 20 s bleaching period,.. Quantified AF (qAF) was calculated from the reference gray level (GL), the zero GL, the media and the magnification (refractive error). The linearity of the system, field uniformity, effect of refractive error, and reproducibility were tested. qAF measurements were then done on 22 patients with Stargardt disease (STGD ) and 11 patients with retinitis pigmentosa (RP). Results The linear detection range extended to 175 GL. Field uniformity was better than 5% in a central 20°‐diameter circle. The recorded AF and the square of the image magnification were inversely related. Different day reproducibility was 4.1 % at the fovea. Median inter‐instrument reproducibility (Spectralis and the HRA2) was 7.4 %. Normals. qAF highly correlated with age (central qAF = 8.8+3.5*Age, p<0.00001). STGD. Background levels of qAF were elevated up to 4 times age‐matched controls; fleck levels were twice background. RP. HyperAF rings had significantly higher levels than controls and correlated with inner segment/outer segment junction loss. Conclusion Modified SLO instrumentation and analytic methods that account for optical media density and refractive error allow non‐invasive, in vivo quantitative AF measurements (total lipofuscin fluorescence) relative to a fixed internal standard in normal subjects and patients with retinal degenerations to monitor disease progression and response to therapy.