Localisation and significance of in vivo near-infrared autofluorescent signal in retinal imaging
- Steffen Schmitz-Valckenberg1,2,3,
- David Lara1,4,
- Shereen Nizari1,
- Eduardo M Normando1,
- Li Guo1,
- Alfred R Wegener3,
- Adnan Tufail2,
- Fred W Fitzke1,
- Frank G Holz3,
- M Francesca Cordeiro1,5
- 1Institute of Ophthalmology, University College London, London, UK
- 2Medical Retina Service, Moorfields Eye Hospital, London, UK
- 3Department of Ophthalmology, University of Bonn, Bonn, Germany
- 4Imperial College London, The Blackett Laboratory, London, UK
- 5Western Eye Hospital, London, UK
- Correspondence to Dr Steffen Schmitz-Valckenberg, Department of Ophthalmology, Ernst-Abbe-Str. 2, 53127 Bonn, Germany;
- Accepted 1 August 2010
- Published Online First 29 September 2010
Aim To evaluate near-infrared (NIR) autofluorescence (AF) in patients with geographic atrophy (GA) secondary to age-related macular degeneration and to investigate the origin of the signal by in vivo and histological analysis in rats and in a human donor eye.
Methods Confocal scanning laser ophthalmoscopy in vivo imaging, including blue (excitation: 488 nm, emission 500–700 nm) and NIR (excitation: 790 nm, emission >810 nm) AF was performed in 21 eyes of 18 GA patients. Pigmented and albino rats underwent with the same device both in vivo and post-mortem imaging. For the latter, cryostat prepared retinal cross-sections were imaged using an additional customised magnification lens. Finally, cross-sections of a 49-year old human donor eye were recorded.
Results Atrophic areas in GA were characterised by low NIR AF intensities. In the junctional zone of atrophy, focal areas of increased intensity were seen which appeared to seldom correlate to blue AF findings. Confocal live scanning in pigmented rats identified the maximum of the NIR AF signal in the outer retina, with histological confirmation of the signal origin localised to the retinal pigment epithelium and sclera in both animals and human donor eye. No NIR AF was found in the retina of young non-pigmented rats.
Discussion This study further underscores the assumption that melanin is the main source of NIR AF in the healthy retina. Increased NIR AF intensities in the junctional zone in GA may represent accumulation of melanolipofuscin, which may reflect disease activity and thus may allow for early identification of patients at high-risk of GA enlargement.
- Fundus autofluorescence
- scanning laser ophthalmoscope
- age-related macular degeneration
- near-infrared imaging
- experimental and animal models
Linked articles 187344.
Funding Supported by Sharp-Eye Research Fellowship, European Commission FP5, HPRN-CT-2002-00301, Foundation Fighting Blindness and Wellcome Trust.
Competing interests None.
Patient consent Obtained.
Ethics approval Ethics approval was provided by the Moorfields & Whittington Local Research Ethics Committee, REC reference number: 06/Q0504/109.
Provenance and peer review Not commissioned; externally peer reviewed.