- Visual field tests measure peripheral vision — how far you can see in 8 directions from center
- Add up all 8 measurements, divide by 8 — this gives you the average concentric contraction
- Each eye is rated separately — then combined using VA's visual field rating table
- Normal field is 500° total — any significant reduction may warrant a rating
Below is an example of how to calculate visual field impairment:
Looking at the chart, note each of the eight lines and the points at which the vision 'ring' touches each of the directional lines.
Left Eye
| Direction | Point of Intersection (°) |
|---|---|
| Temporally | 30 |
| Down temporally | 30 |
| Down | 20 |
| Down nasally | 20 |
| Nasally | 20 |
| Up nasally | 20 |
| Up | 20 |
| Up temporally | 20 |
Now we add everything up 30 + 30 + 20 + 20 + 20 + 20 + 20 + 20 = 180.
Great! Now we need to get the average impairment so, divide 180 by 8.
180/8 = 22.5
Our Veteran here has an average concentric contraction of 22.5° for their left eye.
Right Eye
| Direction | Point of Intersection (°) |
|---|---|
| Temporally | 85 |
| Down temporally | 80 |
| Down | 60 |
| Down nasally | 5 |
| Nasally | 60 |
| Up nasally | 55 |
| Up | 45 |
| Up temporally | 60 |
You should have gotten an average concentric contraction of 62.5°.
Technically, their right eye has no impairment as it has the a total field of vision of 500°. But I hope it reinforced the concept for you in any event.
Now onto the ratings!
Plugging the average impairments into the Visual Field Rating Schedule would have given you an evaluation of 10% for the left eye and no rating for the right eye.