Abstract
Fluorescence lifetime imaging ophthalmoscopy (FLIO) is a novel technique that measures in vivo autofluorescence intensity decay over time of endogenous fluorophores in the retina. The Heidelberg Engineering FLIO system was used to obtain two 30 degree scans centered on the fovea of both eyes. The FLIO system uses a 473nm blue scanning laser light source and the emitted fluorescence is detected in two wavelengths channels, short and long spectral channels (SSC, LSC). Since the mydriatic status influence the FLIO result, the impact of mydriasis on FLIO need to be clarified. In this prospective, observational study, the impact of mydriasis on measurements from fluorescence lifetime imaging ophthalmoscope (FLIO) images in normal subjects were evaluated. 12 healthy participants (24 eyes) were volunteered and all subjects were scanned twice and the mean fluorescence lifetime (τm) values were computed with dilation and without dilation on different days. Intraclass correlation coefficients (ICC) and coefficients of variation (CV) were calculated from the measured τm in dilated, nondilated and between the dilated and non-dilated setting. Test duration was also compared and correlated with lifetimes in both settings. Repeatability was excellent for both the dilation and non-dilation settings (ICC; 0.967–0.996; 0.926–0.986, respectively). The agreement between the dilation and non-dilation settings, however, were lower (ICC; 0.688–0.970). The τm in the non-dilation setting was significantly longer than in the dilation setting for the SSC (P<0.05). The FLIO test duration in the non-dilation setting was significantly longer than with dilation for the SSC (P <0.05). Although good repeatability in τm measurements between imaging sessions were observed both with and without dilation, the agreement was not as good when comparing dilated with non-dilated measurements. Since FLIO without mydriasis results in longer τm in the SSC and takes a longer time for image acquisition, maximal dilation is recommended for FLIO testing.
Highlights
Fluorescence lifetime imaging ophthalmoscopy (FLIO) is a novel technique that measures in vivo autofluorescence intensity decay over time of endogenous fluorophores in the retina, such as lipofuscin, advanced glycation end products (AGE), collagen, and elastin [1,2,3,4,5]
Standard FLIO image acquisition is usually performed with maximally dilated pupils to reduce the influence of the crystalline lens and to increase the time-correlated photon counts from retinal fluorophores [7]
Among the 14 volunteers, FLIO results from 2 subjects were excluded because of poor quality of images obtained without dilation
Summary
Fluorescence lifetime imaging ophthalmoscopy (FLIO) is a novel technique that measures in vivo autofluorescence intensity decay over time of endogenous fluorophores in the retina, such as lipofuscin, advanced glycation end products (AGE), collagen, and elastin [1,2,3,4,5]. Because fluorescence lifetime is specific for each fluorophore, the decay of fluorescence intensity after pulse excitation permits the differentiation of fluorophores with overlapping emission spectra. It can produce quantitative data based on the lifetimes of the different endogenous retinal fluorophores [1,6]. Dysli et al reported that the FLIO allows reproducible measurements of fluorescence lifetimes even with nondilated pupils. They found that the agreement of mean fluorescence lifetimes between dilated and nondilated pupils were not as good when compared with the agreement between two measurements with nondilated pupils [1]
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