I suffer from astigmatism. It's only mild, though I feel it's affecting what I'm seeing when looking through the viewfinder. Frequently, after shooting a photo with my Canon EOS 7D, I'll load it into Lightroom and discover that what looked sharp as an LCD preview is actually not at all in focus when you get down to the 1:1 level.
Normally I let auto-focus do all the work, so I attribute this to back-focusing effects that I'm not picking up on when looking through the viewfinder.
Today, I switched to manual focus while using my tripod to see if I could do a better job than the AF. Rocking the focus ring back and forth, I found it hard to distinguish the point where my subject is in focus (blurry -> slightly blurry -> blurry); indeed, when I got back to Lightroom I still found about a third of my shots came out slightly off-focus.
Is there anything that I can try that could improve my shots, particularly anything that would reduce/nullify the effect of my eyesight while using the camera? The obvious answer to this could be "wear glasses" -- which I do, but not while using the camera, as I feel like they're in my way every time I peer through viewfinder!