Shortest τ originates from MP-containing retinal layers, especially from the Henle fibre layer. Fluorescence lifetime imaging ophthalmoscope (FLIO) provides information on the MP distribution, the pathogenesis and topology of MH. Macular pigment (MP) fluorescence may provide a biomarker for monitoring pathological changes in retinal diseases.

ABSTRACT.Purpose: To discriminate non-proliferative diabetic retinopathy (NPDR) patients from healthy controls by fluorescence lifetime imaging ophthalmoscopy (FLIO). Methods: A prototype FLIO (Heidelberg-Engineering, Heidelberg, Germany) was used to examine the retina of 33 patients and 28 controls. As increased fluorescence of the diabetic lens is known, the lenses of 34 patients and 24 controls were investigated as well. Time-resolved decay was detected in two spectral channels (ch1: 498-560 nm, ch2: 560-720 nm) and approximated by a series of three exponential functions yielding in lifetimes (s 1 , s 2 , s 3 ), amplitudes (a 1 , a 2 , a 3 ) and their amplitude-weighted means (s m ). Results: Significant differences between patients and controls were found for all fundus lifetime components (s m , s 1 -s 3 ) as for the amplitude a 3 in both spectral channels. Channel 1 showed the largest differences: the average of mean fluorescence lifetime s m in the macula was 259 AE 137 ps in the patients versus 147 AE 69 ps in the controls. A logistic regression model allowed discrimination between study and control group with a sensitivity of 90.09% and a specificity of 71.4% (area under the curve: 0.865). Significantly shorter s m in the patients group than in the control group was detected in channel 2 in the crystalline lens (1587 AE 326 ps versus 1854 AE 384 ps, p = 0.006). Conclusions: Fundus Fluorescence lifetimes are significantly increased in NPDR while lens lifetimes are shorter in the patient group. Lifetime changes might be indicative for the accumulation of advanced glycation end products (AGEs) which enables detection of the disease with high sensitivity and specificity possibly bearing diagnostic merit.

Using FLIO, we present a novel way to detect foveal sparing, investigate MP, and analyse variability of τ in different foveal regions (including the prognostic valuable border region) in GA. These findings support the potential utility of FLIO in monitoring disease progression. The findings also highlight the possibly protective effect of lutein supplementation, with implication in recording the presence and distributional pattern of MP.

Fluorescence lifetime imaging ophthalmoscopy (FLIO) is a new imaging modality in ophthalmology. For clinical investigations, the amplitude-weighted mean of two or three lifetime components is usually analyzed. In this study, we investigated the effects of fixation of lifetime components. This resulted in slightly higher fit errors but mean lifetimes were highly correlated to those from fits with variable individual lifetimes. Furthermore, this approach resulted in a similarly good discrimination of diabetic retinopathy patients from controls, a reduction of the computational workload, a de-noising of the mean lifetime images and allows higher local resolution. Thus, fixation of lifetimes in the fit of FLIO data could be superior for clinical routine analysis of FLIO data.

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