To evaluate longitudinal changes in retinal nerve fiber layer thickness (RNFL) and visual field in patients with normal tension glaucoma (NTG).

Thirty eyes of 30 NTG patients and 30 eyes of 30 normal control subjects were enrolled in the present study. RNFL thickness was measured using optical coherence tomography (OCT), and visual field tests were performed using a Humphrey visual field analyzer at baseline and 23.3 ± 15.3 months later. Changes in RNFL thickness at each clock-hour segment and visual field sensitivities were analyzed. The rates of change in RNFL thickness were also calculated.

Significant differences in RNFL thickness were observed between NTG patients and normal control subjects at the 5, 6, 7 and 12 o'clock positions at baseline ( p < 0.001). At follow-up, the RNFL thickness change was not significant for normal control subjects, although it was significant for NTG patients at the 4, 5, 6, 7, 11 and 12 o'clock positions ( p < 0.001). Visual field parameters did not change significantly in the normal control subjects or NTG patients. The reduction rates of RNFL thickness were 0.38 µm/month for the NTG patients and 0.11 µm/month for the normal control group, displaying a 3.5-fold faster reduction rate for NTG patients.

The NTG group showed greater reductions in RNFL thickness in the upper and lower sectors over time; however, the visual field parameters did not change significantly. The results suggest that progression of glaucoma can be detected in an earlier stage using OCT than can be detected using a visual field test.