Glaucoma refers to a group of diseases that affect the optic nerve and involves a loss of retinal ganglion cells in a characteristic pattern. It is a type of optic neuropathy. Raised intraocular pressure is a significant risk factor for developing glaucoma (above 22 mmHg or 2.9 kPa). (Glaucoma (Wikipedia).
My friend lost one eye to glaucoma when he was still young. If only this report, Experimental and clinical evidence of neuroprotection by nerve growth factor eye drops: Implications for glaucoma published in Proceedings of the National Academy of Sciences had been published earlier. The report claimed that eye drops containing containing nerve growth factor seemed to trigger chemical changes within cells that prevent those cells from dying in response damages from increased intraocular pressure and may boost the capacity of healthy RGCs (retinal ganglion cells) to form new connections within the optic nerve, compensating for any damage that may have already taken place.
The researchers from the University of Rome treated rats with induced with glaucoma through injection of hypertonic saline into the episcleral vein, with eye drops containing 2 does of NGF - 100 and 200 μgm/ml.
For further details, refer to BBC News (health) and Proceedings of the National Academy of Sciences of the United States of America