Investigation of long-wavelength fundus autofluorescence

• Applicant: Dr. Martin Gliem
• Subject Area: Ophthalmology
• Term: from 2017 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 386950012

Fundus autofluorescence (AF) imaging of the retina with confocal scanning laser ophthalmoscopy has been established as a non-invasive imaging modality for the diagnosis of retinal and macular diseases. Long-wavelength near-infrared autofluorescence (excitation: 787 nm) is a new, innovative alternative to the classic autofluorescence imaging using 488 nm blue excitation light. Excitation of the fluorophores at the ocular fundus using a longer wavelength has several advantages: 1. The examination is more comfortable for the patient (no glare). 2. The image quality is less affected by cataract development facilitating imaging in older subjects. 3. Visualization of the central retina is not affected by macular pigment. 4. The lower energy of the longer wavelength is less likely associated with retinal light toxicity. 5. The different origin of the signal (melanin) offers new pathogenic insights.With the current imaging technique the autofluorescence signal and thus image quality is considerably lower compared to conventional blue-light autofluorescence. This may be the main reason for the currently limited application and scarce scientific publications on this technique.Therefore, the first objective will be to optimize the method of long-wavelength autofluorescence imaging. For this purpose an additional laser source (700 nm) will be integrated into a scanning laser ophthalmoscope and the performance with regards to image quality will be investigated systematically using different excitation wavelengths and filter combinations.In the next subproject, the signal intensity will be quantified using an integrated fluorescent reference. First, factors affecting measurements will be identified, followed by generation of a normative database. Finally, subjects with various retinal diseases will be investigated and compared to the normative database.In the last subproject, the clinical relevance and applicability of long-wavelength autofluorescence imaging will be investigated. First, the detection of certain disease characteristics in early and intermediate AMD (e.g. drusen) will be assessed and compared to conventional imaging techniques. Furthermore, the benefit for the differential diagnosis and prognostication in retinal dystrophies will be investigated. Finally, patients with Choroideremia undergoing retinal gene therapy will be examined to assess the applicability as potential read-out for gene therapy studies.The results of this study will not only contribute to the establishment of a more comfortable and potentially less toxic examination technique but also to a better understanding of pathogenic pathways of various retinal diseases.

• DFG Programme: Research Fellowships
• International Connection: United Kingdom
• Host: Professor Dr. Peter Charbel Issa, Ph.D.