Anyone who has ever been examined for eye disease involving blood flow in the retinal capillaries—as people with diabetes routinely are to assess vision loss associated with their disease— remembers the test: the injection, the bright lights, the discomfort.
Now researchers from the University of Indiana offer a new non-invasive technique using near-infrared light that allows them to see blood flow within all capillaries of the light sensitive tissues in the retina at the back of the eye. With it, they can detect changes in blood vessels while the patient remains shot-free and relatively comfortable. “Our work enables us to measure the smallest capillaries using near infrared light, without injection of contrast agents,” explains Stephen Burns, who is leading the research effort at Indiana, “and thus it holds significant promise for safely investigating retinal vascular changes in disease.”
The traditional means of visualizing the retina is known as fluorescein angiography. It involves a shot in the arm of fluorescein dye that travels within seconds through the blood to the eye where it highlights flow and vessel integrity in the small capillaries in the retina. A series of photographs is taken to document the capillary network and reveal defects or changes. If vessels are damaged or abnormal, dye leaks out. Many shot-adverse patients find the procedure repellent enough that they put off getting these crucial eye exams.
To develop a patient-friendly alternative, Burns and his colleagues turned to adaptive optics that uses a confocal scanning laser opthalmoscope to produce retinal images in real time. A mirroring system helps guide the imaging beam to build a montage of the area being investigated. “In general, we could generate maps within a single imaging region without operator intervention once frames were chosen for alignment,” Burns says.
Medical research is a cornerstone of Frontiers in Optics 2008 (FiO), the 92nd Annual Meeting of the Optical Society (OSA), being held Oct. 19-23 at the Riverside Convention Center in Rochester, N.Y. FiO 2008 will take place alongside Laser Science XXIV, the annual meeting of the American Physical Society’s Division of Laser Science. Presentation FWW6, “Constructing Human Retinal Capillary Maps from Adaptive Optics SLO Imaging,” will be presented on Oct. 22.
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