Putting on someone else's glasses

How come when you put on someone else’s glasses (like to see if you look good in the frames) it makes you nauseous (if the prescription is radically different from yours)? What’s the physiology behind this, i.e., connection between eyes and stomach?

Just like getting sea-sick (travel-sick) in a car: your eyes tell the brain one thing (things are blurry, so I must be moving), but the balance sensor in your inner ear tells the brain another thing (nothing moving), which confuses the brain. Confused brain reacts to the sympathic system, which controls largely the stomach, which gets sick.

Actually, the first reaction from wrong glasses I’d expect are headaches, with feeling nauseous after that, but it probably depends on how far off your axiomatic (?) vision is. That is, besides the curve of the glass, a lot of wrong-sighted people also have the axis of their eyeball aligned wrong, (which is why each pair of glasses is measured to you personally). If your eyes and the wrong glasses are very far apart, that can cause a very disorienting picture in your brain’s sight center.

Emphasis added. Not only do things look blurry, but they can also be distorted and cause perceived motion just in the way things look as you pan your head around. This adds to the brain/inner-ear sensory confusion that you mention as the cause of the nausea.

I thought this thread was going to be about how disgusting it is when someone insists on trying on your glasses. Face grease. Yuk.

Nausea is a happy response to a disagreement between visual and inner-ear stimuli, because (unless you are in a cabin in a moving vehicle or sitting stock-still in front of a FOV-filling motion picture screen) this is a pretty good indicator that you may have ingested something toxic. Expeditious ejection of the contents of the stomach under these circumstances is a good policy.

I actually experience very slight, brief motion-sickness/nausea when I change between my contacts and my glasses (unless I’m spending a lot of time wearing both). My prescription is fairly powerful, which seems to result in a definite distortion of my vision through either the contacts, the glasses, or both–but after a few minutes I get used to it and compensate. Somene else’s glasses would have a different sort of distortion entirely, I imagine.

As a person with uncorrected vision, the first thing I notice when I try someones glasses on is a strong sense of my eyes trying to focus. It seems as if I can literally feel the muscles hunting around trying to focus in. Eventually this stops and the headache starts to set in. Haven’t kept any glasses on long enough to get to nauseated.