Cornea - transparent shell (film), covering the front of the eye. Cornea bordered by an opaque outer shell eyes - the sclera (albuginea).
The theory of accommodation of Hermann von Helmholtz (1821-1894) (German physics) is not correct, the vision is not built at the expense of the ciliary muscle (Helmholtz suggested that the ciliary muscle is a semi-circle lens fits, narrows and widens the lens itself) and change of curvature of the lens.
PS the lens never have the curvature.
PS ciliary muscle is not a semi-circle lens fits, but only forms a pupil.
William Horatio Bates (1860-1931) proved that the main work in the process of accommodation play a 6-th oculomotor muscles. Accommodation make due to change in length of the eye in general.
Since then, as Helmholtz mistake people had become victim of glasses business, as well as laser eye surgery.
Some are not literate oculists say that you have the cornea is curved, or astigmatism of the cornea, therefor you have bad vision. Bates explains here illiteracy.
Modern ophthalmology at the wrong theory of Helmholtz said that the accommodation make due to the ciliary (photosensitive) muscle that forms the pupil. Bates discovers that the fish do not have this ciliary muscle. So how the fishes can see? Can modern ophthalmology explain astigmatism, myopia and hypermetropia in -> fishes?
Bates is writing, that the eye may be blind, it may be suffering from atrophy of the optic nerve, from cataract, or disease of the retina, but so long as it does not try to see, the external (ciliary) muscles act normally and there is no error of refraction, so how modern ophthalmology may explain this?
At a time when you notice that you see bad in that time you can restore your vision during a few months by the method of Bates. Will any oculist tell your about it? No, why should they fumbled with you, put to you a glasses and deal with it.
Spectacles and contact lenses cause tremendous harm to the eyes, glasses and contact lenses develop astigmatism oculomotor muscles, the second is due to spikes eyes in the eyes sockets are not movable.