Glaucoma is a group of eye diseases that result in damage to the optic nerve and potentially leads to irreversible blindness . The nerve damage involves loss of retinal ganglion cells in a characteristic pattern [2–5] with intraocular pressure (IOP) the only modifiable risk factor and IOP reduction the only treatment. Previous studies have reported that vascular factors may play a critical role in the development of glaucoma in addition to elevated IOP [3–7].