Longitudinal nerve fibre layer thickness change in normal-pressure glaucoma

Purpose: To investigate longitudinal retinal nerve fibre layer (RNFL) thick ness change in patients with normal-pressure glaucoma (NPG) and to assess h ow this may be related to visual fields. Methods: NPG patients and normal s ubjects who had had serial GDx nerve fibre layer Analyzer II imaging and Hu mphrey visual fields performed at least 18 months apart were selected for s tudy. These measurements were compared between groups at baseline and at su bsequent follow-up, for change over time. Results.: Seventy five NPG patien ts and 35 normal subjects were studied. Significant differences in RNFL thi ckness were found between NPG patients and normal controls at baseline (P l ess than or equal to0.001). Over the same time, there was great-er RNFL thi nning in NPG patients than in normal subjects (P less than or equal to0.000 1). RNFL thinning in NPG was negatively correlated with visual field log MD at baseline (P<0.001) and change in MD over time (P<0.001). Conclusion: Re duction of RNFL thickness over time was significantly greater in NPG patien ts than in normal subjects, indicating that NPG patients' RNFL had thinned at a faster rate. NPG patients with initially better visual fields had a gr eater reduction in RNFL thickness than did those with initially more advanc ed visual field defects, suggesting that more RNFL change may be observed w hen glaucoma is at an earlier stage. There was a direct relationship betwee n RNFL thinning and visual field deterioration.