About vision: The human eye
The eye works much like a camera. Light enters the eye through the cornea via the pupil at the center of the iris, the colored part of the eye. The pupil controls the amount of light admitted while the cornea does most of the focusing. Light then passes through the lens, where it is finely focused, and travels back through the eye to the retina. The retina interprets images and then sends the information to the brain via the optic nerve.CORNEA
The cornea is sometimes referred to as the "window of the eye". It is composed of 5 layers of tissue. Its outer layer (the epithelium) provides protection for the eye. The epithelium is made up of highly regenerative cells that have the ability to grow back within 3 days, allowing for fast healing of superficial injuries. Most of the inner layers of the cornea provide strength to the eye.PUPIL
This is the black circle in the middle of the eye. The primary function of the pupil is to control the amount of light entering the eye. When you're in a bright environment, the pupil becomes smaller to allow less light through. When it's dark, the pupil expands to allow more light to reach the back of the eye.IRIS
This is the colored part of the eye surrounding the pupil. The primary function of the iris is to control the size of the pupil. This is achieved through contraction or expansion of the muscles of the iris.SCLERA
The sclera is the white part surrounding the iris. The sclera's purpose is to provide structure, strength, and protection to the eye.LENS
The lens is the clear structure located behind the pupil. Its primary function is to provide fine-tuning for focusing and reading. The lens performs this function by altering its shape. At about the age of 45, the lens becomes less flexible. At about the age of 65, the lens becomes cloudy and hard, preventing light from entering the eye.VITREOUS BODY
This is the clear gel-like substance located inside the eye's cavity. Its purpose is to provide a spherical shape to the eye. The vitreous body may develop small clumps known as 'floaters', which are especially common in nearsighted people.RETINA
The retina consists of fine nerve tissue which lines the inside wall of the eyes and acts like the film in a camera. Its primary function is to transmit images to the brain.OPTIC NERVE
This nerve carries images from the retina to the brain.