Another important tool used to examine and measure the optic nerve is the visual field test. This measures how well the optic nerve functions in carrying visual information to the brain. Most visual field tests measure the ability of the patient to recognize light at each area of the retina. Testing of the visual field and examination of the optic nerve are the most important determinants of whether or not there is glaucoma. If glaucoma is present, they also allow your eye doctor to determine whether it is stable or becoming progressively worse.
Most patients dislike having their visual field tested.
The test is often long, tiring, and boring. It is not uncommon to feel that you have performed badly. Most modern visual field machines keep testing each spot measured until the patient misses, in order to determine the dimmest light detectable. Thus, it is necessary to have many misses to complete the test. Missed points, however, may be perfectly normal and should not cause one to be upset.