Monitoring macular pigment in geographic atrophy using FLIO

Purpose : The pathophysiology of geographic atrophy (GA) is not yet fully understood and prognostic factors are still under discussion. Little is known about how the macular pigment (MP) changes during the progress of the disease. Monitoring fundus autofluorescence (FAF) lifetimes in GA using Fluorescence-lifetime-Imaging-Ophthalmoscopy (FLIO) may lead to novel insights, especially since FLIO can detect MP. Methods : Using FLIO (Heidelberg-Engineering, Heidelberg, Germany), time-resolved FAF of 20 eyes with GA has been recorded in two spectral channels (ch1: 498-560nm; ch2: 560-720nm) and approximated by a series of three exponentials, resulting in three lifetimes: (τ1-τ3). Their amplitude-weighted mean (τm) per channel and pixel was utilized as the main parameter for statistical analysis. A FAF image was acquired with each measurement; OCT scans and fundus photography were obtained. τm was averaged over the standardized ETDRS grid and the area of the fovea (diameter 0,1mm). Of special interest were differences between the fovea and the Inner Ring (IR) of the grid. These differences (τm (IR) minus τm (fovea)) were correlated to the best corrected visual acuity (BCVA). Results : Mean FAF lifetimes in GA differ according to the individual progression of the disease. Additionally to hypo- and hyperfluorescent regions detectable with FAF, FLIO visualizes differences within these regions: The presence of MP results in shorter FAF lifetimes (250-400 ps) compared to other atrophic regions (>700 ps) (figure 1). These short FAF decays are often related to a spared fovea. The τm differences between the IR and the Fovea (τm (IR) minus τm (fovea)) correlate with the BCVA (r:0.6; p<0.01 for both channels). Conclusions : Whereas conventional FAF images only show differences in the fluorescence intensity, FLIO can additionally distinguish between different atrophic areas, better showing the presence of MP, resulting in different lifetimes and possibly detecting spared regions. FLIO is a new imaging method to monitor GA. If FLIO can provide information on the GA progression needs to be further evaluated. This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016

Fundus autofluorescence lifetimes and spectral features of soft drusen and hyperpigmentation in age-related macular degeneration

Purpose: To investigate the autofluorescence lifetimes as well as spectral characteristics of soft drusen and retinal hyperpigmentation in age-related macular degeneration (AMD). Methods: Forty-three eyes with nonexudative AMD were included in this study. Fluorescence lifetime imaging ophthalmoscopy (FLIO), which detects autofluorescence decay over time in the short (SSC) and long (LSC) wavelength channel, was performed. The mean autofluorescence lifetime (τm) and the spectral ratio (sr) of autofluorescence emission in the SSC and LSC were recorded and analyzed. In total, 2760 soft drusen and 265 hyperpigmented areas were identified from color fundus photographs and spectral domain optical coherence tomography (SD-OCT) images and superimposed onto their respective AF images. τm and sr of these lesions were compared with fundus areas without drusen. For clearly hyperfluorescent drusen, the local differences compared to fundus areas without drusen were determined for lifetimes and sr. Results: Hyperpigmentation showed significantly longer τm (SSC: 341 ± 81 vs. 289 ± 70 ps, P < 0.001; LSC: 406 ± 42 vs. 343 ± 42 ps, P < 0.001) and higher sr (0.621 ± 0.077 vs. 0.539 ± 0.083, P < 0.001) compared to fundus areas without hyperpigmentation or drusen. No significant difference in τm was found between soft drusen and fundus areas without drusen. However, the sr was significantly higher in soft drusen (0.555 ± 0.077 vs. 0.539 ± 0.081, P < 0.0005). Hyperfluorescent drusen showed longer τm than surrounding fundus areas without drusen (SSC: 18 ± 42 ps, P = 0.074; LSC: 16 ± 29 ps, P = 0.020). Conclusions: FLIO can quantitatively characterize the autofluorescence of the fundus, drusen, and hyperpigmentation in AMD. Translational Relevance : The experimental FLIO technique was applied in a clinical investigation. As FLIO yields information on molecular changes in AMD, it might support future diagnostic