FLIO Images Earliest Retinal Changes

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Fluorescence lifetime imaging ophthalmoscopy (FLIO), a novel im­aging modality that reveals specific patterns in almost any fundus disor­der, may one day serve as a tool for visualizing early retinal changes in myriad retinal disorders.

While the role of FLIO is still evolving, researchers expect FLIO to be “a cornerstone for retinal imaging in the future,” said Martin S. Zinkernagel, MD, PhD, at University Hospital Bern in Bern, Switzerland, and coauthor of a review of FLIO.¹ In proof-of-concept studies, he said, “We and other groups have provid­ed [evidence] that FLIO can provide unique information to complement that [which is] obtained through other imaging modalities.”

What is FLIO? Like convention­al fundus autofluorescence (FAF), FLIO is mainly a qualitative imaging procedure. (It relies on a modified Heidelberg Spectralis platform, which is not yet a standard prod­uct.) In contrast, unlike FAF, FLIO can provide quantitative analysis by measuring the fluorescence lifetime of fluorophores.

In other words, FLIO is a tool that tells how long any given retinal fluorophore glows after excitation with a laser pulse. This span of time is known as fluorescence lifetimes.

FLUORESCENT LIFETIMES. Macular hole, before surgery (A) and 3 months after successful closure of the hole (B).

Pilot studies. Comparisons of mean lifetimes of diseased eyes to healthy controls have revealed FLIO’s potential for monitoring disease progression and therapeu­tic outcomes, Dr. Zinkernagel said. He added that FLIO has provided information on potential markers for disease progression in retinal hered-itary disorders and macular degen­eration, suggesting it may be used in clinical trials on gene therapy for these diseases.

In addition, earlier this year, researchers reported using FLIO to better understand the pathogenesis of drusen in AMD. They found that soft drusen associated with AMD progression showed longer flu­orescence decays than did hard drusen. Thus, they hypothesized, FLIO might give information about the individual risk for the development of late AMD.²

Looking forward. Although Dr. Zinkernagel predicted that FLIO will become an important diag­nostic technology, its precise use is yet to be revealed. “Whether it will be used in an academic setting or by ophthalmologists in practice is difficult to predict based on the current knowledge.”

—Miriam Karmel

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1 Dysli C et al. Prog Retin Eye Res. Published online June 30, 2017.

2 Sauer L et al. Time-resolved fundus autofluorescence in dry AMD. Present­ed at: ARVO; May 9, 2017; Baltimore.

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Relevant financial disclosures—Dr. Zinkernagel: National Cancer Insti­tute/National Institutes of Health: S; Swiss National Science Foundation: S.

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