Evaluation of Efficacy of 20 µg/ml rhNGF New Formulation (With Anti-oxidant) in Patients With Stage 2 and 3 NK

The primary objective of this study is to evaluate the efficacy of 20 µg/ml 6 times a day of rhNGF eye drops solution (formulation containing anti-oxidant) compared to vehicle (formulation containing anti-oxidant) given 6 times a day. The evaluation of efficacy is intended as: * complete healing of stage 2 (persistent epithelial defect) and 3 (corneal ulcer) neurotrophic keratitis (NK) as measured by the central reading center using corneal fluorescein staining, * assessing the duration of complete healing, * improvement in visual acuity and improvement in corneal sensitivity.