The stability of the 3D feature was greatly improved on the New Nintendo 3DS, which added eye-tracking using the front-facing camera so that you could tilt and

The stability of the 3D feature was greatly improved on the New Nintendo 3DS, which added eye-tracking using the front-facing camera so that you could tilt and turn it and you wouldn't see a double image. I've never personally heard of anyone ever getting a headache from it, and it would be a bit silly not to use it because it doubles the screen resolution and makes everything much sharper.