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Longitudinal nerve fibre layer thickness change in normal-pressure glaucoma
D Poinoosawmy1, J C Tan, C Bunce
1Glaucoma Research Unit, Moorfields Eye Hospital, City Road, London EC1V 2PD, UK.
Purpose:
To investigate longitudinal retinal nerve fibre layer (RNFL) thickness change in patients with normal-pressure glaucoma (NPG) and to assess how this may be related to visual fields.
Methods:
NPG patients and normal subjects who had had serial GDx nerve fibre layer Analyzer II imaging and Humphrey visual fields performed at least 18 months apart were selected for study. These measurements were compared between groups at baseline and at subsequent follow-up, for change over time.
Results:
Seventy-five NPG patients and 35 normal subjects were studied. Significant differences in RNFL thickness were found between NPG patients and normal controls at baseline (P < or = 0.001). Over the same time, there was greater RNFL thinning in NPG patients than in normal subjects (P < or = 0.0001). 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:
Reduction of RNFL thickness over time was significantly greater in NPG patients than in normal subjects, indicating that NPG patients' RNFL had thinned at a faster rate. NPG patients with initially better visual fields had a greater reduction in RNFL thickness than did those with initially more advanced visual field defects, suggesting that more RNFL change may be observed when glaucoma is at an earlier stage. There was a direct relationship between RNFL thinning and visual field deterioration.