Even if your sight seem to be fine, without the need of use glasses, this doesn't rule out glaucoma because glaucoma is a silent disease. Glaucoma initially reduces your peripheral vision without other symptoms, leaving the central detailed vision unaffected until a later stage. It does not affect the ability of the eye to focus.
Visual field test is a simple way to determine if you are experiencing vision loss from glaucoma. Glaucoma slowly and painlessly destroys sight if it is not detected and treated.
Visual field testing involves staring straight ahead into a display and clicking a button when you notice a blinking light in your peripheral vision. The visual field test is simple nad may be repeated at regular intervals to make sure you are not developing blind spots from damage to the optic nerve or to determine the extent or progression of vision loss from glaucoma. The earlier the disease is detected, the more successful the treatment is.
Imaging of the optic nerve and surrounding tissues is an objective test that can also detect glaucoma damage and progression. However, at this time it has not replaced the visual field test.