Figure 4. Improvement in preexisting visual field damage in patients with normal tension glaucoma after treatment with GBE. Patients are divided in two groups according to sequences of treatment. Group A: sequence of treatment: GBE- wash out- placebo. Group B: sequence of treatment: placebo-washout-GBE. GBE=Gingko biloba. Reproduced with permission from Quaranta et al. [82].