dwebb66
Member
I'm not an ophthalmologist (but I did date one once), but I did get a degree in Physics and I've had a number of semesters with optics (albeit, it was 20+ years ago).
If you're looking for an explanation, I think the most likely cause is refraction/reflection due to the windshield being made up of multiple layers.
The windshield is likely a sandwich of multiple layers of glass and plastic (e.g. tint, UV film, etc.). Refraction occurs when light passes through different mediums. What's likely happening is the light is being refracted, and then some is being split and reflected (probably twice) and forming the ghost image above/below the actual image.
During the day, there isn't enough contrast to notice the issue, but at night headlights and streetlights have a very high contrast that makes it very obvious.
The relative angle of the windshield would also be a factor.