Purpose:
To present spatial optic disc oxygenation maps from a group of glaucoma patients and to demonstrate the correspondence between oxygenation maps and structural measures.
Methods:
Eleven patients (20 eyes, mean age 71 ± 8 years) with primary open-angle glaucoma, glaucomatous visual field defect, age >40 years, no other ophthalmic disease, and refractive error less than +/-5.00DS equivalent and/or 2.00DC were recruited from the clinics of Manchester Royal Eye Hospital, UK. Patients undertook HRT3 (Heidelberg Retina Tomograph, Heidelberg Engineering GmbH, Germany) and multispectral imaging of the optic disc. Multispectral imaging was carried out with a modified digital fundus camera system incorporating a 150W xenon arc light source and a fast-tuneable liquid crystal filter (Varispec, Cambridge Research Systems, UK). Images were taken with 8 different wavelengths of light selected according to the reflection properties of retinal blood components (range 496-700nm, total acquisition time <1.68s). Pixel-by-pixel oxygenation maps were calculated from the aligned multispectral images using the Beer-Lambert law.
Results:
Oxygenation maps were calculated for all 20 imaged eyes. In all eyes areas of low oxygenation were found to correspond to areas of cupping measured by the HRT3. The figure shows 2 typical examples where in the oxygenation maps (left) brighter areas represent higher oxygenation and darker areas represent lower oxygenation. These correspond well with the HRT3 topography images (right) where the red areas represents the areas of cupping.
Conclusions:
Spatial oxygenation maps calculated from multispectral images show correspondence to optic disc structures and may provide additional information on optic disc perfusion in glaucoma patients.
Keywords: optic disc • imaging/image analysis: clinical • oxygen