Visual field defects and normal nerve fiber layer: May they coexist in primary open-angle glaucoma?

The retinal nerve fiber layer (RNFL) is the anatomical structure most sensi tive to glaucoma injury. Before a functional loss such as a visual field de fect is displayed, a large number of nerve fibers can be damaged. However, there are glaucoma patients in which an apparently normal RNFL coexists wit h evident visual field defects, A total of 54 eyes affected with primary op en-angle glaucoma were studied, Visual field was examined with the Humphrey Field Analyzer (Zeiss) using program 30-2. The Nerve Fiber Analyzer II (La ser Diagnostic Technologies) was used to study the RNFL of these patients. Mean deviation of the visual field ranged from 6 to 31 dB in all eyes that were examined. The average thickness of the RNFL ranged from 20 to 90 mu m. According to our previous experience 75 mu m was fixed as the cutoff betwe en normal and pathological values of RNFL thickness. We identified 5 eyes w ith a RNFL thickness over 75 Cim and a visual field with a mean deviation o ver 6 dB; 9% of the studied eyes were found to have a visual field defect w ith no changes in RNFL. We conclude that not all subjects have the same num ber of fibers at birth and that it is therefore possible to underestimate t he RNFL changes. Our study illustrates that the concept of normal and alter ed has to be considered as a relative one for all the aspects characterizin g the glaucomatous disease. Copyright (C) 2000 S. Karger AG,Basel.