Retinal nerve fiber layer thickness in glaucoma patients with small visual field defects compared to healthy subjects as measured with HRT, NFA and OCT
M. Klemm, E. Rumberger, R. Schwartz, V. Knospe, B. Fuisting
Introduction: Throughout the course of glaucoma, retinal nerve fiber layer (RNFL) thickness decreases and visual field defects increase. This study was performed to answer the question if retinal nerve fiber thinning precedes visual field changes.
Methods: RNFL thickness of 45 healthy subjects and 45 glaucoma patients with a small visual field defect (mean deviation £ -5 in automated perimetry with Humphrey Field Analyzer) as measured with Heidelberg Retina Tomograph (HRT), Nerve Fiber Analyzer (NFA) and by Optical Coherence Tomography (OCT) were compared. The data were analysed separately for the superior, inferior, nasal and temporal quadrant of the retina.
Results: There was no significant difference in perimetric findings between glaucoma patients and controls. Both groups showed similar mean deviations. In contrast, RNFL thickness in the inferior quadrant showed significant differences (p<0.05) between healthy subjects and glaucoma patients as measured with HRT (323 µm versus 268 µm), NFA (87 µm versus 77 µm) and OCT (93 µm versus 86 µm). Similar results were obtained for the superior quadrant with NFA and OCT.
Discussion: Our results suggest that glaucomatous damage can be detected earlier by methods of RNFL thickness measurements than by perimetry. Further studies need to be performed to study the changes in RNFL thickness and visual field defects throughout the course of glaucoma.
Eye Clinic, University Hospital Eppendorf, Martinistr. 52, D-20246 Hamburg