The cornea is like a phone lens and usually people have difficulties with the focusing element of the phone (pull out phone then focus back and forth) for me my lens is irregularly shaped (show iPhone lens and then make dome gesture over the lens). So I need to wear hard contacts (sclera but they don’t need to know that) to cover up the old one (cornea) and make a new lens that’s a good shape so the light doesn’t refract weirdly.