Abstract
Purpose:
The fluorescence of organic molecules is not only characterized by the emission spectrum, it has also a specific decay rate or lifetime. Fluorescent lifetime imaging ophthalmoscopy is a new imaging method that allows measurements of fluorescence lifetimes in vivo in the retina. We wished to assess the feasibility of obtaining fluorescent lifetime data from eyes with retinal vein occlusion (RVO) using a novel fluorescence lifetime ophthalmoscope, the FLIO, based on a Heidelberg Engineering Spectralis® system.
Methods:
Fluorescence lifetime measurements of retinae of healthy controls and patients with RVO were conducted. Fluorescence decay times were measured in a short wavelength channel (498 - 560 nm) and in a long wavelength channel (560 - 720 nm). Short fluorescent lifetimes (tau1), long fluorescent lifetimes (tau2) and mean fluorescence lifetimes (tau mean) in each channel were calculated for each acquired pixel within the retina by time-correlated single photon counting. For comparison purposes an EDTRS grid was used to average fluorescent lifetimes for different retinal areas. Fluorescent lifetimes in areas affected with RVO were compared with corresponding healthy retina using a student’s t test.
Results:
Average fluorescence lifetimes in the retinal areas affected by RVO were generally longer in both the long and short wavelengths channels when compared to healthy retina. For the short wave length channel (498 - 560 nm) average fluorescent lifetimes were 665.3 picoseconds in the areas affected by RVO versus 479.7 picoseconds in healthy retina (p=0.014). For the long wave length channel (560 - 720 nm) the average fluorescent lifetimes within RVO affected retina was 457.3 picoseconds versus 399.6 picoseconds in healthy retinae (p=0.0085).
Conclusions:
We were able to show that RVO leads to specific and quantifiable changes in fluorescent lifetimes in the human retina. Fluorescent lifetime imaging of the retina is a promising new technique that may serve as additional tool to diagnose retinal diseases and may be useful for early detection of metabolic changes in the retina.
Keywords: 550 imaging/image analysis: clinical •
688 retina •
552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)