In the previous page I introduced the Optimal Visual Volume (OVV) for a person with normal vision. Let’s consider now, how would this apply for a person with impaired vision?
Applying Standard Reserves to Alice’s VV
In theory, the same reserves would apply. That is, we could step in from the patients VV by a standard level of reserve all around, which would directly map out their OVV. Here’s how that would look for Alice, our archetypal patient with mild-to-moderate AMD:
Again the normal VV is show in magenta as a comparison. It’s easy to see that Alice’s OVV is getting quite small. Now let’s compare Alice’s OVV with the normal VV:
Notice how Alice’s OVV doesn’t encompass the range of most common print sizes, even at optimal levels. In practical terms, it means that Alice might still be able to read most things, but not comfortably.
Applying Standard Reserves to Bob’s VV
Let’s do the same for Bob, our archetypal patient with more advanced AMD:
The thing to take note of here is that Bob’s OVV is almost gone. For Bob to read with fluency and comfort, he’s going to need very high contrast print that is also very large, which is quite a practical challenge.