title: Combination of confocal principle and aperture stop separation improves suppression of crystalline lens fluorescence in an eye model.
abstract: Fluorescence lifetime imaging ophthalmoscopy (FLIO) is a new technique to detect changes in the human retina. The autofluorescence decay over time, generated by endogenous fluorophores, is measured in vivo. The strong autofluorescence of the crystalline lens, however, superimposes the intensity decay of the retina fluorescence, as the confocal principle is not able to suppress it sufficiently. Thus, the crystalline lens autofluorescence causes artifacts in the retinal fluorescence lifetimes determined from the intensity decays. Here, we present a new technique to suppress the autofluorescence of the crystalline lens by introducing an annular stop into the detection light path, which we call Schweitzer's principle. The efficacy of annular stops with an outer diameter of 7 mm and inner diameters of 1 to 5 mm are analyzed in an experimental setup using a model eye based on fluorescent dyes. Compared to the confocal principle, Schweitzer's principle with an inner diameter of 3 mm is able to reduce the simulated crystalline lens fluorescence to 4%, while 42% of the simulated retina fluorescence is preserved. Thus, we recommend the implementation of Schweitzer's principle in scanning laser ophthalmoscopes used for fundus autofluorescence measurements, especially the FLIO device, for improved image quality.
authors.affiliation: Institute of Biomedical Engineering and Informatics, Technische Universität Ilmenau, POB 100565, 98694 Ilmenau, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Klemm
authors.affiliation: Institute of Biomedical Engineering and Informatics, Technische Universität Ilmenau, POB 100565, 98694 Ilmenau, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Blum
authors.affiliation: Institute of Biomedical Engineering and Informatics, Technische Universität Ilmenau, POB 100565, 98694 Ilmenau, Germany.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Link
authors.affiliation: Experimental Ophthalmology, University Hospital Jena, Bachstraße 18, 07740 Jena, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Hammer
authors.affiliation: Institute of Biomedical Engineering and Informatics, Technische Universität Ilmenau, POB 100565, 98694 Ilmenau, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Haueisen
authors.affiliation: Experimental Ophthalmology, University Hospital Jena, Bachstraße 18, 07740 Jena, Germany.
authors.forename: Dietrich
authors.initials: D
authors.lastname: Schweitzer
keywords: (170.4460) Ophthalmic optics and devices; (170.4470) Ophthalmology; (300.2530) Fluorescence, laser-induced