What are the symptoms of glaucoma?
BMJ Group Medical Reference
At first, glaucoma doesn't cause any symptoms. Then it starts to affect your eyesight, but only slowly. You may not notice your eyesight getting worse for many years.
Glaucoma can eventually cause blindness, although most people with glaucoma don't go blind. Glaucoma does not hurt.
The poor eyesight starts with small blind spots at the edge of your vision. They are easy to miss, and many people don't notice them. Without treatment, the blind spots get slowly bigger until you can see only things that are directly in front of you. It can feel like you're looking down a tunnel. 
Also, some people with severe glaucoma: 
Can't see properly when moving from a lighter to a darker room
Can't judge the height of steps and curbs, so they may trip over frequently.
About 1 in 5 people with glaucoma already have badly damaged eyesight before they are diagnosed. 
About 9 in 10 people with glaucoma are diagnosed by their eye doctors after routine eye tests.   Experts say you should have regular check-ups as you get older, especially if you are black, or if someone in your family has glaucoma.  You only need to take three simple tests to find out if you have glaucoma, high pressure inside your eye, or both. 
The information here is about long-term (chronic) glaucoma. A second kind of glaucoma, called acute glaucoma, comes on suddenly and is very different. Your eyes quickly become painful and red, and you may get a severe headache and sickness. Your vision becomes blurred and you may notice haloes (rings) around lights. Acute glaucoma is an emergency. If you get these symptoms, see a doctor straight away. You need urgent treatment.
For references related to Glaucoma click here