Foveal Fluorescence Lifetimes Provide Insight Into Geographic Atrophy

In geographic atrophy (GA), shorter foveal fluorescence lifetimes (fFLT) are associated with foveal sparing (FS), and these features in eyes with a loss of foveal sparing suggest an earlier stage of disease, according to research published in Retina. 

In the current study (ClinicalTrials.gov identifier NCT01981148) researchers sought to assess the longitudinal changes of fFLT in patients with and without FS in GA due to dry age-related macular degeneration (AMD), as well as to describe temporal changes in fFLT and to investigate cases of persisting short fFLT in eyes without foveal sparing. 

Researchers recruited participants with GA secondary to dry AMD from the outpatient department of ophthalmology at the University Hospital of Bern in Switzerland. All participants underwent a baseline and follow-up examination by an ophthalmologist which included best-corrected visual acuity (BCVA) testing, slit lamp examination, and dilated fundus examination. Spectral-domain optical coherence tomography (OCT) and blue-light FAF were also conducted. 

Fluorescence lifetimes of the retina were retrieved using a prototype fluorescence lifetime imaging ophthalmoscope (FLIO) device. The study cohort included 33 eyes from 19 patients (11 women, 8 men). Mean age was 77.9 years at baseline and 82.8 years at follow-up. At baseline, 10 eyes (30%) demonstrated foveal sparing; of these, 6 exhibited persistent foveal sparing at follow-up. In a subgroup of pseudophakic patients, 19 eyes from 12 patients were analyzed. 

Investigators found a decrease in BCVA per year for the entire cohort of -1.64±0.38 ETDRS letters. In the pseudophakic cohort, the yearly BCVA decrease was similar: -1.46±0.42 letters. 

fFLT increased yearly by an average (±SEM) of 47±17 ps and 29±10 picoseconds (ps) in the long spectral channel (LSC) of the complete cohort and by 32±11 ps in the short spectral channel (SSC) and 24±9 in the LSC in the pseudophakic subgroup. 

In pseudophakic eyes with foveal sparing, fFLT prolonged yearly by 39±11 ps in the SSC and 30±13 ps in the LSC. In the group with persistent foveal sparing at follow-up, fFLT prolonged yearly by 32±7 ps and 16±7 ps in SSC and LSC, respectively. 

When investigators correlated BCVA of all eyes with corresponding fFLT, a significant correlation for both spectral chambers at baseline and follow-up was noted. In the pseudophakic group, no significant correlations at baseline and follow-up were noted. 

Macular pigment optical density (MPOD) value at follow-up at 0.5˚ eccentricity was 93±36 area under the curve (auc), and 814±396 auc at 2˚. In the pseudophakic subgroup, these values were 136±59 auc and 1282±627 auc, respectively. 

When MPOD values were correlated with respective fFLT, researchers saw a significant correlation at both 0.5˚ and 2˚. 

Study limitations include the small number of patients, particularly the small number with foveal sparing, the longitudinal nature of the study, potential confounding bias, and the inclusion of MPOD measurements in eyes impacted by GA. 

“Short fFLT may be retained even in eyes with no foveal sparing,” according to the research. “While higher BCVA was reported to correlate with shorter fFLT and thereby indirectly indicating a functioning central retinal metabolism, this correlation is not valid in these cases.” 

“Furthermore, they do not seem to represent a different disease entity, but more so an earlier stage of disease, as they show a faster decline in BCVA and more pronounced increase in fFLT per year,” the report explains. 

Reference

Lincke J-B, Dysli C, Jaggi D, Solberg Y, Wolf S, Zinkernagel MS. Longitudinal foveal fluorescence lifetime characteristics in geographic atrophy using fluorescence lifetime imaging ophthalmoscopy (FLIO). Retina. Published online July 17, 2021. doi:10.1097/IAE0000000000003222