Does excessive computer screen use before an eye exam mess with the results?

The key word here is excessive.
You don’t want eye strain before a test.
You also don’t want to use marijuana for a day or two before a test.

I think you already know the answer, and just confirming it. You used the term “excessive” and everyone knows “excess” of almost everything is bad, be at excess sleeping, excess work or excess use of computer.

And of course it can mess with results due to head and eye strain.

An eye exam is based on how your eye focuses light. I don’t see what this has to do with computer use. I have never heard anyone say that you should avoid excessive computer use before driving.

Doing anything excessively will cause problems!!! You can die from drinking too much water too fast!!!