Abstract
Purpose: :
To prevent the development of visual field defects in glaucoma it is necessary to develop methods for the quantification of early structural damage. Aim of this study was to investigate the retinal nerve fibre layer thickness (RNFL) with a spectral domain, high-resolution OCT (SOCT) in patients with ocular hypertension (OHT), early and advanced glaucoma in comparison to healthy controls.
Methods: :
33 healthy controls, 8 patients with OHT (normal visual field, healthy optic disc appearance, IOP > 21 mmHg), 8 preperimetric open angle glaucoma patients (normal visual field, glaucomatous disc atrophy, IOP > 21 mmHg) and 16 patients with perimetric open angle glaucoma (glaucomatous visual field loss and disc atrophy, IOP > 21 mmHg) were investigated using a serial Spectralis HRA+OCT (Heidelberg Engineering, Germany). Segmentation of retinal nerve fibre layer in 32 sectors was performed after export of 3.4 mm diameter circle scans centred on the optic disc. One eye of each patient was selected for statistic analysis. Mean global values as well as sector data were compared using Mann-Whitney-U test.
Results: :
Normals showed mean RNFL thickness of 88.80±8.35µm with the highest values in the inferior sector (112.11±11.80µm). Patients with perimetric glaucoma demonstrated a significant reduction of overall RNFL thickness (53.60±16.32µm; p=0.0001) as well as in all investigated sectors (p<0.04), in contrast in preperimetric patients RNFL loss occurred predominantly in the temporal inferior (87.10±18.5µm), temporal horizontal (54.30±5.24µm) and temporal superior sector (89.14±20.10µm)(p<0.02). OHT showed only a trend, but no significant reduction of RNFL thickness (p>0.05). Interestingly RNFL loss was as pronounced in the papillo-macular bundle as in the superior temporal sector in all glaucomas.
Conclusions: :
Routine SOCT allows fast and high resolution assessment of the retinal nerve fibre layer. Significant reduction (17-22 %) of RNFL was detected in early glaucoma prior to visual field loss. Retinal nerve fibre loss was more pronounced in the temporal inferior, followed by the temporal superior and even temporal horizontal sector for early glaucoma stages.
Keywords: optic nerve • nerve fiber layer • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)