Abstract
Purpose :
With the increasing application of funduscopically invisible retinal laser treatments, a sensitive method enabling the detection of small structural and metabolic changes is desired. Aim of this study was to apply the fluorescence lifetime imaging opthalmoscopy (FLIO) to monitor the sites of laser irradiation to identify its potential in the evaluation of laser-induced tissue changes.
Methods :
Seven eyes of Chinchilla bastard rabbits were treated in vivo using a diode laser with a wavelength of 514 nm, spot diameter of 85 µm and single pulses with duration of 5.2 or 50 µs with different power settings. FLIO (excitation at 473 nm, detection with short spectral channel (SSC, 498-560 nm) and long spectral channel (LSC, 560-720 nm) was conducted directly and one week after irradiation. Structural changes were examined by optical coherence tomography (OCT).
Results :
Selective damage of retinal pigment epithelium (RPE) was induced with the shorter pulse duration with the power up to 5.6 W, while visible photocoagulation was achieved with the longer pulses and maximum power of 11 W. Directly after irradiation the FLT at laser spots was highly extended (SSC: 1142±109 ps; LSC: 461±47 ps) compared to the one in the non-irradiated periphery (SSC: 705±35 ps; LSC: 211±20, p<0.01). The FLT around photocoagulation was also significantly longer (SSC: 738±45 ps; LSC: 229±22 ps), whereas it was rather shorter at the further surrounding (SSC: 637±55 ps; LSC: 182±28 ps) (p<0.01). At the sites of selective RPE damage, the FLT was slightly longer in the nearby surroundings directly after irradiation, whereas, after one week, shortened over wider region, up to about 1000 µm from the spots. The longer FLT in the nearby surroundings directly after irradiation corresponded to the hypofluorescent area in fundus autofluorescence (FAF), and also to the disruption of ellipsoid zone and external limiting membrane in OCT. These changes in FAF and OCT were no more visible after one week.
Conclusions :
Extension of FLT at laser spots is considered due to RPE damage, whereas the longer FLT in their surroundings directly after irradiation might be a result of temporary change of photoreceptor, and the later shortening due to tissue metabolic alterations. FLIO may therefore be a sensitive tool to monitor subtle structural as well as metabolic changes following laser treatment.
This is a 2021 ARVO Annual Meeting abstract.