Disclaimer: I have no formal medical or vision science training. Please point out any factual errors.
My test is based on the idea that Glaucoma is indicated by pressure on optic nerve, which one may not even be aware of but slowly destroys the nerve (which is actually a bundle of nerves, similar to a huge communications cable) from the outside of the cable in. The effect of this is a gradual loss of vision from the periphery toward the center, forming tunnel vision and eventually total blindness. The mind compensates so the person doesn't even realize that their field of vision is being narrowed until it is too late.
Doctors test for vision loss at the periphery by snapping fingers at the periphery and seeing if the patient can see it.
With my test you simply look straight ahead and raise your arms into a circle around your head, similar to a ballet dancer:
Slowly move the elbows forward while continuing to look ahead. If you have to move your elbow on either arm significantly forward (consult an eye doctor to "calibrate" your elbows) then you may have damage to the periphery of the optic nerve. If so, the further forward, the more the damage.
Damage to the optic nerve is, with current technology progressive and never regressive so acting quickly is of the utmost importance.