Repeatability of Fluorescence Lifetime Imaging Ophthalmoscopy in Normal Subjects With Mydriasis

We evaluate the repeatability of fluorescence lifetime imaging ophthalmoscopy (FLIO) in normal subjects with mydriasis and explore factors that influence FLIO imaging.

Thirty-two healthy participants (63 eyes) were enrolled in this prospective study. The Heidelberg Engineering FLIO system uses a 473 nm blue laser light and the emitted fluorescence is detected in two wavelength channels, short and long spectral channels (SSC, LSC). The mean fluorescence lifetime (τ_m) values were computed for the entire scan area as well as in five regions of interest (ROI, 1 × 1 mm) at the fovea and superior, nasal, inferior, and temporal portions of the macula. Intraclass correlation coefficients (ICC) and coefficients of variation (CV) were used to assess the repeatability. Age, macular thickness, and vascular density also were correlated with τ_m.

The repeatability was good for both channels (ICC, 0.956∼0.995; CV, 9∼16%). The τ_m for the entire scan was 367.8 ± 58.1 picoseconds (ps) in SSC and 322.5 ± 34.0 ps in LSC. τ_m was the shortest in the fovea and significantly shorter in the temporal region compared to other regions. τ_m was positively correlated with age (r = 0.588 for SSC and r = 0.584 for LSC, P = 0.000) and retinal thickness (r = 0.298 for SSC and r = 0.322 for LSC, P = 0.000), and negatively correlated with vascular density (r = -0.112, P = 0.055 for SSC and r = -0.119, P = 0.040 for LSC).

Repeatable fluorescence lifetime values can be obtained with FLIO, but the lifetimes are affected by age, retinal thickness, vessel density, and macular location.

Establishing repeatability of FLIO can introduce fluorescence lifetime imaging technique, which is used in basic science for analysis of excitation and emission wavelength spectrum of fixed and living cells into clinical practice.