Hi there!
Symptoms of glaucoma can either be from build-up of pressure within the eye, or visual loss as a result of the high pressures.
Glaucoma can be broadly divided into two categories, "open" or "closed" angle, depending on the configuration of the drainage angle of the eye, where fluid (aqueous) is drained out of the eye. Depending on the rate of build-up of pressure, glaucoma can be further described to be "acute" (or sudden), or "chronic" (or gradual).
In most cases of open angle glaucoma and chronic closed angle glaucoma, the build-up of pressure is gradual, and without symptoms. Some patients may experience some glare and haloes around lights when the pressure is high. Additionally, there is a sub-group of glaucoma known as "normal tension glaucoma" in which the eye pressures are normal, but the optic nerve continues to be damaged. These patients will not have any symptoms from high pressures since the eye pressures will be in the normal range.
Visual loss from glaucoma usually starts from the peripheral field of vision, so blurring of vision due to involvement of central visual field is a late sign, when glaucoma is in its intermediate to advance stages.
Acute angle closure glaucoma, however, presents with dramatic symptoms of eye redness, pain, blurring of vision, together with headache, nausea, vomiting. This is due to the rapid and extreme build-up of eye pressure within the eye. This is an emergency and immediate medical attention should be sought.
Hence, most cases of glaucoma are without noticable symptoms in the early to intermediate stages. Patients who are at risk of developing glaucoma (such as those with a family history of glaucoma, who are moderately to severely short or long sighted, or have poorly controlled hypertension, diabetes, or have had previous injury or surgery to the eye) should get their eyes screened for glaucoma.
I am sorry to learn that your uncle has been diagnosed with glaucoma -- I hope his condition is in its early stages; I would strongly recommend that his family members (especially first degree relatives) get screened so that treatment be started, if necessary, to prevent irreversible visual loss.
Hope this helps!
Regards,
DQ
