Patterns of endothelial nitric oxide synthase (eNOS) expression in retinal ischemia were studied utilizing a transient high intraocular pressure (HIOP) model. We investigated neuronal cell damage and changes in eNOS immunoreactive expression in the ischemic retina, and its relationship to the neuroprotection of betaxolol treatment after ischemic injury. Immunohistochemical staining for eNOS was performed at 3, 7, 14 and 28 days after ischemia/reperfusion. In controls, eNOS immunoreactivity was detected in retinal vessels, but was not detected in neurons. After ischemia/reperfusion, the intensity of eNOS immunoreactivity increased in both retinal vessels and the ganglion cell layer (GCL) compared with controls. eNOS-positive neurons were induced first in the inner nuclear layer (INL) 7 days after reperfusion. However, when experiments were carried out on animals that had been treated with betaxolol after ischemia/reperfusion, the intensity of eNOS immunoreactivity decreased compared to the untreated ischemic retinas. These results suggest that an increase in eNOS expression could be associated with the degenerative changes in the ischemic retina, and that betaxolol treatment appears to protect retinal tissue from ischemic damage.