Abstract
Purpose :
Soft drusen and retinal hyperpigmentation are among the main risk factors for progression of age-related macular degeneration (AMD). We investigated the autofluorescence (AF) lifetimes as well as spectral autofluorescence characteristics of these lesions in relation those of the retinal pigment epithelium (RPE).
Methods :
43 patients (mean age: 74.1±7.9 years) with non-exudative AMD and no geographic atrophy were included. Fundus AF from a 30° retinal field was investigated with the Heidelberg Engineering Spectralis®-based fluorescence lifetime imaging ophthalmoscope (FLIO), detecting the decay of the fluorescence over time in a short (498-560 nm; SSC) and a long (560-720; LSC) wavelength channel upon excitation with <100 ps laser pulses at 473 nm. The amplitude weighted mean fluorescence lifetime (tm) was calculated from a three-exponential approximation of the decay. The spectral ratio (sr) of fluorescence emission in SSC and LSC was calculated. Drusen and hyperpigmented areas were identified from color fundus photographs and SD-OCT images and segmented in the AF images. Fluorescence lifetimes as well as sr were obtained within the inner and outer ring of the standardized early treatment diabetic retinopathy study ETDRS-grid centered at the macula. Differences in tm and sr between RPE and drusen/hyperpigmentation were tested by using a paired t-test.
Results :
There was no significant difference in tm between soft drusen and RPE (SSC: 284±54 vs. 280±57ps; LSC: 337±34 vs. 334±40 ps; N=34), however, the sr was significantly higher in drusen (0.555±0.077 vs. 0.529±0.081, p<0.0005). Hyperpigmentation showed significantly longer tm than RPE (SSC: 341±81 vs303±85ps, p<0.0005; LSC: 406±42 vs. 357±40 ps, p<0.0005; N=23) and the sr was higher (0.621±0.077 vs. 0.545±0.076, p<0.0005).
Conclusions :
FLIO can be used to quantitatively characterize the fluorescence of RPE, drusen, and hyperpigmentation in AMD. While soft drusen show a green-shift of fluorescence emission, the fluorescence lifetimes from hyperpigmentation show an additional prolongation in comparison to values from the RPE. This may contribute to the generally prolonged lifetimes found in AMD.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.