One visible sign of glaucoma is a red eye, according to Mayo Clinic. This sign happens during acute angle-closure glaucoma. Other outward signs of glaucoma can be swollen and red-rimmed eyelids, change of color in the iris and watery eyes, according to the University of Michigan Kellogg Eye Center.
Because these signs are so nonspecific, and because the more common primary open-angle glaucoma often has no outward signs at all, it is important that people over 40, as well as those with risk factors, have regular eye examinations, according to Mayo Clinic.
Acute angle-closure glaucoma is a medical emergency, states Mayo Clinic. Besides the reddening of the eye, the pain in the eye is severe and is accompanied by nausea and vomiting. The patient also has a severe headache and may have blurred vision, see halos around lights and experience other visual disturbances. If the condition isn't remedied quickly, the patient can go blind, according to the University of Michigan Kellogg Eye Center
On the other hand, the symptoms of primary open-angle glaucoma are gradual, painless and subtle, states Mayo Clinic. The patient loses peripheral vision over time, which usually happens in both eyes. In advanced stage glaucoma, the patient has tunnel vision. Once these symptoms appear, they can't be reversed. As with acute angle-closure glaucoma, the patient can eventually go blind.