Advances in imaging technology continue to improve

November 1, 2005

Newport Beach, CA—Imaging technology for quantitative assessment of the optic nerve and retinal nerve fiber layer (RNFL) can be a useful supplemental tool to clinicians, especially when the diagnosis of glaucoma is uncertain based on other clinical information, said Donald L. Budenz, MD, MPH, at Innovations in Glaucoma.

"None of the imaging devices should be relied on as a substitute for patient evaluation with visual field testing and optic disc stereophotography in diagnosing glaucoma," said Dr. Budenz, associate professor of ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami. "However, the data they provide can be helpful in cases where the other test findings are indeterminate and the clinician is deciding between starting lifelong therapy for a patient or continuing with careful follow-up."

Innovations in Glaucoma was a continuing medical education activity jointly sponsored by The New York Eye and Ear Infirmary and Ophthalmology Times with an unrestricted grant from Pfizer Ophthalmics.

Confocal scanning laser ophthalmoscopy (CSLO) is also now in its third generation as the Heidelberg Retinal Tomograph 3 (HRT3, Heidelberg Engineering). CSLO creates a topographic map of the optic nerve head. The latest system offers improved scan registration to increase performance reliability for detecting glaucoma onset and its progression.

"This new version is able to track the position of earlier scans and replicate that for repeat testing for more accurate evaluation of changes between examinations," Dr. Budenz explained.

Confocal scanning laser polarimetry with variable corneal compensation (GDx-VCC, Carl Zeiss Meditec) is used to measure RNFL thickness. Relative to OCT, the GDx-VCC offers an advantage of generating results that seem to be more operator-independent.

"We use OCT at our institution but have found there may be some variability introduced when switching technicians," Dr. Budenz said. "However, the manufacturer's engineers are working to develop an image registration system that will address that shortcoming."

A team at Carl Zeiss Meditec is currently working on a number of projects to enhance this system further, he said. A review software package that will allow GDx users to manipulate and print GDx data from a laptop will be available soon, he added.