20/20 (6/6) vision is considered normal. A person with 20/20 vision can see at 20 ft (6 m) what people with normal vision can see at this distance.
- When the second number is smaller than the first number, the person's vision is better than normal. For instance, a person with 20/10 (6/3) vision can see from 20 ft (6 m) what people with normal vision can see from 10 ft (3 m).
- When the second number is larger than the first number, the person's distance vision is worse than normal.
- A person with 20/200 (6/60) vision or less in his or her best eye when wearing corrective lenses is considered legally blind.
Your doctor will also tell you if you have reduced near vision.
The doctor tests your eyes with different lenses until the lens that corrects your vision the best (sometimes better than 20/20 or 6/6) is found. The result of a refraction test determines your prescription eyeglass or contact lens strength.
Visual field test
Normally, a person's visual field forms a rough circle with a natural blind spot. If your vision is normal, you should be able to see objects clearly throughout the entire visual field except for the area with the natural blind spot. When you are using both eyes to see, the blind spots do not interfere with your vision.
You may have vision loss in certain areas of the visual field if you are not able to see:
- Test objects during tangent screen testing.
- Movements or light flashes during perimetry testing.
Abnormal results during Amsler grid testing include:
- Not being able to see the black dot at the center of the grid.
- Not being able to see all four edges of the grid.
- Having blank spots or dark spots on the grid (other than the black dot at the center).
- Seeing lines that look wavy or curved.
Gaps in different parts of the visual field may have many causes, including eye diseases (such as glaucoma and macular degeneration) or nervous system problems (such as stroke). If results on any of the visual field tests are abnormal, you will need further tests to determine the cause.
Color vision test