Suddenly the eye can only see half, which is often referred to as acute visual field damage, there are three common causes: 1, retinal branch vein obstruction. Retinal vein obstruction leads to retinal blood flow obstruction, causing chronic ischemic and hypoxic retinal nerve cell damage, causing overall damage to the retina, and eventually visual field damage. 2, retinal detachment, the retinal neuroepithelium and pigment epithelium detachment, resulting in detachment of the scope of visual field damage. 3, retinal branch artery obstruction. Retinal branch artery obstruction is an acute ischemic and hypoxic optic nerve injury, and the visual field at the site of that injury will also be significantly impaired. Regardless of which type of injury has occurred, prompt hospital consultation is required to avoid affecting the remaining visual acuity as well as the residual visual field.