Most focusing problems are due to the shape of the eye. If the cornea is too steep or too flat in curvature, this can create short-sightedness or long-sightedness and other distortions in vision.
What we do with laser vision correction, is use a special laser to smooth off and reshape the surface of the eye to correct those focusing problems.
It typically forms in the corner of the eye closest to your nose and can often extend across the surface of the cornea.
Though they can look a little scary they’re largely harmless, but they can grow across your pupil and cause vision problems – most famously to premier NZ cricketer Ross Taylor. (While flogging 290 against Australia in 2015, he had to take regular breaks to insert eye drops, then had the growth successfully removed.)