According to The Merck Manual Home Health Handbook, light travels through the sclera, cornea, pupil and lens before stopping at the retina, respectively. Once at the retina, the information from the light is converted to electrical impulses for the brain to interpret.
The Merck Manual Home Health Handbook describes the sclera as the eye's tough, outer covering. It is transparent, allowing light to pass through. Next, light passes through the cornea. The cornea roughly focuses light towards the pupil. The pupil is a dark circle in the center of the eyeball. It is surrounded by the iris, which constricts and expands to change the size of the pupil. Acting similarly to a camera's aperture, it regulates the amount of light that enters the eye's interior.
After entering the pupil, that light passes through the lens. The lens is responsible for fine focusing light. It does this by slightly altering its shape to bend light rays at the correct angles. The light then lands on the retina, which is a surface at the back of the eye that is covered in photoreceptors. Photoreceptors sense different types and wavelengths of light that are converted into electrical signals. The optic nerve delivers these signals to the brain where they are decoded into images, notes The Merck Manual Home Health Handbook.
