the cornea protects and shapes the eyeball
The lens
The sclera of the eye acts like an outer skin to maintain the spherical shape of the eye.
The ciliary muscle, part of the retina of the eye, changes the focal length of the lens by flattening it or making it more spherical.
It is the lens
No - astigmatism only has to do with the shape of your eye. Floaters are a natural part of aging due to the changes in the jelly-like vitreous in the back of your eye. If you see many floaters, or floaters with flashes of light, make an appointment to see an eye doctor.
Accommodation is the term that means the lens of the eye can change shape. When it changes shape, the eye can focus on items far away or close.
Iris
The lens of the eye also called the crystalline lens.
The most imortant part of the eye that changes the direction of light is the LENS, though the cornea does do a little of the inital focusing.
High blood sugar levels can cause shape changes in the lens of the eye
Muscles in the eye surrounding the lens contract stretching it out, flattening it; or relax, letting it thicken. These changes in shape refocus the lens.
Laser eye surgery permanently changes the shape of the cornea, the clear covering over the coloured iris, and the lens, which is just behind the pupil of the eye
It changes the shape of the cornea, which changes the focal length. Both the cornea and the lens act together (like a compound camera lens) to focus the image on the retina.