Correlation between Retinal Nerve Fiber Layer Thickness and Visual Field in Normal Tension Glaucoma

Purpose: This study was performed to evaluate the validity of optical coherence tomography 3000 (OCT3) in the diagnosis of normal tension glaucoma (NTG). Methods: One-hundred and eighty eyes with NTG or glaucomatous optic disc changes by direct ophthalmoscope and 51 normal eyes were included. Mean deviation (MD) and pattern standard deviation (PSD) were acquired by the Humphrey visual field analyzer. Mean retinal nerve fiber layer (RNFL) thickness was measured by OCT3. We analyzed the relationships between MD and mean RNFL thickness, PSD, and mean RNFL thickness. We also analyzed differences in the change of mean RNFL thickness according to the change of visual field defect progression. Results: MD and PSD were proportional to the mean RNFL thickness, using the Pearson correlation coefficient: 0.418 (p=0.001) and -0.397 (p=0.002), respectively. There was a significant decrease in the mean RNFL thickness according to the visual field defect severity. Particular, the RNFL thickness of the superior and inferior quadrants were significantly decreased in the severe visual field defect groups. The difference between the mean RNFL thicknesses in pre-perimetric glaucoma between the normal eye and early glaucoma groups was not statistically significant. Conclusions: The mean RNFL thickness measured by OCT3 could be considered as valid parameter for the diagnosis of NTG. For early diagnosis of glaucoma, however, visual field test must be considered with OCT3.