Fundus autofluorescence lifetimes are increased in non-proliferative diabetic retinopathy

To discriminate non-proliferative diabetic retinopathy (NPDR) patients from healthy controls by fluorescence lifetime imaging ophthalmoscopy (FLIO).

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 (τ₁ , τ₂ , τ₃ ), amplitudes (α₁ , α₂ , α₃ ) and their amplitude-weighted means (τ_m ).

Significant differences between patients and controls were found for all fundus lifetime components (τ_m , τ₁ -τ₃ ) as for the amplitude α₃ in both spectral channels. Channel 1 showed the largest differences: the average of mean fluorescence lifetime τ_m in the macula was 259 ± 137 ps in the patients versus 147 ± 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 τ_m in the patients group than in the control group was detected in channel 2 in the crystalline lens (1587 ± 326 ps versus 1854 ± 384 ps, p = 0.006).

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.