Abstract
Purpose: :
The accumulation of post-translationally modified proteins as e.g. lipofuscin and advanced glycation end products (AGEs) contribute greatly to the fundus autofluorescence (FAF). The distinct fluorescence spectra of lipofuscin and AGE enable their differentiation in multispecral FAF imaging and might correlate to the HbA1C concentration in patients with Diabetes mellitus.
Methods: :
In a prospective and ethically approved observational study so far 24 eyes of 16 consecutive patients underwent multispectral FAF imaging and a determination of the current HbA1C blood concentration. Fluorescence was excited at 475-515 nm and 476-604nm and recorded at an emission band of 530-675nm. Fluorescence images were taken by a colour CCD camera (colour fluoerscence imaging) enabling the seperate recording of red and green fluorescence. The ratio of green versus red was calculated within a representative region of each image.
Results: :
Multispectral imaging revealed a green-shifted FAF in diabetic patients (mean green/red FAF-ratio: 0.593+/- 0.090). Especially macular fluids (10/16) revealed enhanced green FAF compared to the surrounding flat retina. HbA1C blood concentrations ranged from 5.74 to 10.72% (mean 7.16%). A correlation between the green/red FAF-ratio and an increasing HbA1C in these eyes was only negligible (regression R2=0.0067).
Conclusions: :
Multispectral FAF might non-invasively indicate a higher concentration of AGE in diabetic retinas especially in macular edema, as suggested by green-shifted FAF. However, no correlation of green FAF and increased HbA1C blood concentration was noticed herein. It is specutlated, that a larger number of patients with worse HbA1C concentrations (wider diagnostic window) might be able to proof this hypothesis.
Keywords: diabetes • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical