Why do you do the GDx and the Visual field tests?
They measure different aspects of the nerve. Both are necessary for best evaluation. The Visual Fields test measures functioning nerve fibers. About 300,000 nerve fibers (out of 1 million) have to be lost before the Visual Fields test becomes positive. GDx test is usually more sensitive than the Visual Fields test. Another visual fields test we use is the Frequency Doubling Technology.
