Dual‐wavelength "color" autofluorescence

Abstract

AbstractPurpose To distinguish fluorophores at the human ocular fundus by their different emission spectra.Methods Autofluorescence images were taken from 62 eyes (78.3±6.3 years) with age‐related macular degeneration (AMD), 65 eyes (71.2±8.4 years) with diabetic retinopathy (RD), and 19 eyes (60.7±18.3 years) without any ophthalmic or systemic pathology (control group) by a fundus camera. All eyes were pseudophacic. A 3‐chip color CCD camera was used as detector, recording the fluorescence in two separate spectral bands: Upon excitation at 475‐515 nm, fluorescence was observed at 530‐570 nm and 570‐675 nm. For a global estimation of the fluorescence characteristics, the ratio of the green vs. the red emission (g/r) was calculated in a 70 by 70 pixel area temporal to the macula and apart from pathologic lesions and retinal vessels. Local changes of fluorescence emission spectra were assessed.Results An orange fluorescence was found in the control group. Compared to that group (g/r=0.869±0.073), the global fundus fluorescence of AMD‐patients (g/r=0.906±0.105) and diabetics (g/r=0.974±0.119) was green‐shifted. This shift was statistically significant (t‐test, p=0.001) for the RD and the control group. The optic disc, hypo‐fluorescent atrophic areas (geographic atrophy, laser scars), hyper‐fluorescent drusen, and lipid exudates appeared greenish.Conclusion The ocular fundus autofluorescence is dominated by the orange fluorescence of lipofuscin. The green‐shift of the fluorescence in AMD and RD may indicate protein glycation since advanced glycation end products show green fluorescence. Greenish fluorescence of drusen and exudates reveal non‐lipofuscin fluorescence which needs further clarification. Color autofluorescence visualizes different fluorophores and, thus, may be of diagnostic merit.