Visual acuity is tested ... and forms part of an assessment of ... nerve function

Visual acuity is tested using a Snellen chart or an equivalent. This test measures the sharpness of your vision at a distance and is usually performed in a doctor's office or a vision clinic. Here are the steps:

1. You will be asked to remove your glasses or contact lenses if you wear them.
2. You will be positioned approximately 20 feet away from the Snellen chart. This chart contains rows of letters that get smaller as you move down the chart.
3. Covering one eye, you will be asked to read out the smallest line of letters you can see.
4. The process is then repeated with the other eye.
5. The results from each eye are recorded and compared to what is considered normal vision, which is 20/20.

This test forms part of an assessment of optic nerve function. The optic nerve is responsible for transmitting visual information from the retina to the brain. If your visual acuity is less than 20/20, it could indicate a problem with your optic nerve. Other tests to assess optic nerve function might include a color vision test, an examination of the inside of your eye, or imaging tests like an MRI.