And one should use the Rosenbaum card, which is a miniaturization of the Snellen chart used in optometrist’s office. The best way to do this is to have the patient hold the card at a distance that is the best for him and covering one eye and tell him to cover the eye with his palm, not his fingers because he can see through his fingers and to not mash on the eye, because he can cause the globe to become ischemic and not be able to see in that eye when you test the other eye. So:
-"Sir, could you cover your left eye for me, with your palm like that. Very good, and I want you to read the lowest possible line you can.
Sometimes, I use my pen light to illuminate specifically.
-“Can you, is that the right distance for you?"
-"Four, two, eight, seven, three, nine."
-“It's perfect, you got a 20/20.”
You should then proceed to do the same thing with the other eye. Another important point is to ask the patient does he wear glasses.
-"Do you wear glasses, sir?"
-"No"
Ok, that's important because we in Neurology don't care about the refraction error we care about sudden changes in vision, so we want to test with glasses if they wear glasses or with contact lenses if they wear those. Ok, you don't need to take the glasses off when testing visual acuity in Neurology.