Retinal nerve fiber layer measurement by nerve fiber analyzer in normal subjects and patients with glaucoma.

OBJECTIVE: To identify the pattern of retinal nerve fiber layer (RNFL) loss in glaucoma using the Nerve Fiber Analyzer (NFA). DESIGN: Case-control study. PARTICIPANTS: A total of 80 normal and 75 age- and race-matched chronic open-angle glaucoma subjects were recruited. INTERVENTION: The RNFL thickness was assessed with a scanning laser polarimeter (Nerve Fiber Analyzer GDX, Laser Diagnostic Technologies Inc., San Diego, CA). Analysis of variance was used to compare the corresponding RNFL measurement indices of the different groups. MAIN OUTCOME MEASURES: Superior/nasal (S/N) and inferior/nasal (I/N) ratios of NFA are sensitive parameters to differentiate between glaucoma and nonglaucoma subjects. RESULTS: Peripapillary RNFL measurements at the superior and inferior regions were significantly lower in the glaucoma group (P<0.001) but were similar in temporal and nasal regions (P>0.05). Using nasal value as reference, S/N and I/N ratios were significantly lower in the glaucoma groups (P<0.001) and also decreased with increasing severity of glaucoma. CONCLUSIONS: In glaucoma, RNFL was more susceptible to loss in the superior and inferior regions than in the nasal and temporal regions. The S/N and I/N ratio parameters provided by the NFA appeared to give further discriminating ability in early glaucoma.