Acute glaucoma classically presents with severe pain, redness, and reduced vision in the affected eye, and severe cases can also have systemic symptoms. We report three cases of acute glaucoma in elderly patients. The diagnosis of acute glaucoma in a patient who presents with sudden onset of a painful, red eye with reduced visual acuity, a hazy cornea, and a fixed, semi-dilated pupil is comparatively straightforward. However, any patient with headache, malaise, or gastrointestinal disturbance, especially with clinical signs of an acute red eye and reduced vision, should alert doctors to the possibility of acute glaucoma. This is especially important in elderly people, who may not volunteer any specific ocular symptoms.