Eyeballs

Parts of the eye

• Sclera - The white of the eye
• Cornea - the clear outer surface of the eye
• Aqueous humor - the fluid supporting the cornea
• Pupil - the hole where light enters the eye
• Iris - the Iris is the colored part of the eyeball that contains the muscles that control the opening size of the pupil.
• Ciliary muscle, is a ring of muscle fibers in the eye that control the tendons supporting the natural lens of the eye, and controls the flow of aqueous humor behind the cornea. The Ciliary muscle is controlled by the Ciliary ganglion, which is a complex intersection of several nerve systems. The action of the ciliary muscle is the primary source of accommodation and ciliary spasm which causes pseudomyopia.
• Lens - The part that changes the focus distance of the eye
• Vitreous humor - the gel filling the eye (this is where floaters usually form)
• Rods and cones - the sensory cells of the eye that see light intensity and color
• Retina - the tissue that supports the rods and cones.

Axial Length

The primary cause of differences in refractive state is the length of the eye, referred to as axial length, relative to the focusing power. Long eyeballs are associated with myopia, as the natural lens of the eye focuses light too far forward of the retina.