Background: To measure retinal nerve fibre layer (RNFL) thickness with spectral-domain OCT (SD-OCT) in patients with glaucoma, and to evaluate the correlation between visual field parameters and RNFL thickness.
Methods: Two hundred twelve subjects-55 normal, 37 with preperimetric glaucoma (PPG) and 119 with different stages of primary open angle glaucoma (POAG) were enrolled in this study. Standard automated perimetry was performed in all eyes. RNFL thickness was measured for 6 segments of the 3.4 mm diameter circle and for 8 areas corresponding to the Early Treatment Diabetic Retinopathy Study (ETDRS) grid, both centred on the optic disc. RNFL thickness values were calculated for the inner ring surrounding the optic disc border and the outer ring of the ETDRS grid. The association between visual field parameters and RNFL thickness was evaluated with regression analysis and Pearson correlation coefficients.
Results: In the normal group, mean RNFL thickness was 93 ± 9 μm for circle and 91 ± 14 μm for inner ring, for the POAG group the values were 58 ± 21 μm for circle and 40 ± 21 μm for inner ring, and for the PPG group the values were 77 ± 15 μm and 59 ± 15 μm, respectively. The differences in RNFL thickness between normal and glaucoma eyes were significant (p < 0.001) for all measurements. Mean RNFL thickness between normal and PPG eyes was significantly different for all regions except for the superior-temporal and temporal sector of the circle and for area 7 of the ETDRS grid. In POAG eyes only, RNFL thickness and both mean sensitivity (r = 0.558) and mean defect (r = -0.549) correlated significantly. The best parameters for differentiating normal from PPG eyes were inner ring surrounding the optic disc border (area under receiver operator characteristic curves (AUROC) = 0.940) and area 4 values (AUROC = 0.903) of the ETDRS grid.
Conclusions: SD-OCT showed significantly decreased mean RNFL thickness of the inner ring surrounding the optic disc border of the ETDRS grid by 35% in PPG eyes and by 46% in eyes with early glaucoma compared to the control group. These results support the usefulness of this technology.