Ophthalmologist and glaucoma specialist Dr Daniel Kiage from Innovation Eye Centre Kisii defines glaucoma as a group of eye conditions that damage the optic nerve.
This is typically due to an increase in intraocular pressure (high pressure within the eye).
When the nerve gets damaged, a person starts losing vision.
A normal range for eye pressure is typically between 10 and 20 millimetres of mercury.
Some individuals may develop glaucoma even with pressures within this range, however, Kiage says.
There are different types of glaucoma. Closed-angle glaucoma occurs when the fluid is suddenly blocked and cannot flow out of the eye. This causes a quick, severe rise in eye pressure.
Open-angle glaucoma tends to run in families. A person is at higher risk if they have a parent or grandparent with open-angle glaucoma.
People of African descent are also at higher risk of this disease.