Oxidation causes melanin fluorescence.

Department of Vitreoretinal Surgery, Division of Ophthalmology, University of Cologne, Germany.
Investigative Ophthalmology &amp Visual Science (Impact Factor: 3.66). 02/2001; 42(1):241-6.
Source: PubMed

ABSTRACT The goal of this study is the characterization of the strong yellow fluorescence of oxidized melanin in the retinal pigment epithelium (RPE) and the choroid.
Naturally occurring melanin in the human retina and choroid was oxidized by exposing fixed and plastic-embedded sections of a human eye to light and hydrogen peroxide. Synthetic melanin was also oxidized in vitro by exposure to light and hydrogen peroxide. The fluorescence of oxidized melanin was examined by absorption spectroscopy, fluorescence spectroscopy, and fluorescence microscopy.
Naturally occurring melanin oxidized in situ exhibited a lipofuscin-like yellow fluorescence. Oxidation of melanin in vitro degraded the melanin polymer, resulting in a fluorescent solution. Fluorescence spectroscopy gave an excitation maximum at approximately 470 nm and an emission maximum at approximately 540 nm for both natural and synthetic melanin. Increasing the time of exposure to light or hydrogen peroxide increased melanin fluorescence.
The results indicate that the strong yellow fluorescence of melanin in the RPE and choroid in situ is a property of oxidized melanin and is not due to contamination of the melanin by proteinaceous or lipid materials. The data presented allow a reinterpretation of the results obtained from fluorescence investigations of melanin-containing tissue and suggest a link between melanin degradation and lipofuscin formation.


Available from: Peter Kayatz, Feb 07, 2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background. To evaluate the correlation of fundus autofluorescence (FAF) with indocyanine green angiography (ICGA) in patients with various posterior uveitis disorders. Methods. Interventional case series including 23 eyes of 15 patients with diagnosis of a specific type of retinochoroiditis, such as acute posterior multifocal placoid pigment epitheliopathy (APMPPE), serpiginous-like choroiditis, multifocal choroiditis (MFC), Harada disease, and syphilitic retinochoroiditis. Also, some cases with undefined retinochoroiditis were included. FAF and ICGA were performed and correlated at baseline and during follow-up after treatment. Results. In ICGA, early hypofluorescence was found to be the hallmark of acute choroidal inflammation, resolving in later stages and remaining in the late phase in areas with retinal pigment epithelium (RPE) damage. Poorly defined hyperautofluorescent areas correlated with acute choroidal lesions. Hypoautofluorescent delineation suggested the initiation of RPE healing processes, correlating well with the late phase of ICGA and delineating the RPE damage. Early hyperautofluorescence with late hypofluorescence in ICGA indicated the presence of primary RPE involvement. Conclusion. FAF contributes to the interpretation of RPE disease and may be a useful tool for the follow-up of progressive inflammatory disorders. Comparative evaluation of FAF and ICGA allows a characterization of the sequence of inflammatory events and the level of tissue affected.
    BioMed Research International 01/2015; 2015:247469. DOI:10.1155/2015/247469 · 2.71 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aims of this study are to generate subtraction images of blue-light autofluorescence (BL-AF) and near-infrared autofluorescence (NIR-AF) from normal eyes, eyes with full thickness macular holes, and eyes with irregular foveal contour, and to compare their autofluorescence patterns. This retrospective study included 44 normal eyes of 22 health individuals, 32 eyes with full thickness macular holes of 32 patients, and 36 eyes with irregular foveal contour of 36 patients. BL-AF and NIR-AF were obtained from all patients and used to generate subtraction images using the Image J software. The decreased signal of central patch was recorded. The central foveal thickness (CFT) and outer nucleus layer (ONL) thickness of fovea were measured to calculate the ONL thickness/CFT ratio. The subtraction images showed regularly increased signal in the central macula of all normal eyes. In contrast, decreased signal of central patch was detected in all full thickness macular holes eyes and 26 out of 36 eyes with irregular foveal contour. No significant difference of the ONL thickness/CFT ratio (F = 2.32, P = 0.113) was observed between normal and irregular foveal contour eyes with or without decreased signal of central patch. Both regularly increased signal and decreased signal of central patch were detected in the eyes with irregular foveal contour. Our results suggest that subtraction images are useful for the assessment of certain macular conditions by providing supplementary information to the green-light autofluorescence and BL-AF.
    Lasers in Medical Science 11/2014; 30(1). DOI:10.1007/s10103-014-1693-2 · 2.42 Impact Factor
  • Aerobiologia 01/2015; DOI:10.1007/s10453-015-9365-7 · 1.20 Impact Factor