We use our eyes in virtually everything we do and depend on our vision perhaps more than any other sense we have. Sight is the most precious of the five senses, and many people fear blindness more than any other disability.
The eye allows us to see and interpret the shapes, colors, and dimensions of objects in the world by processing the light they reflect or give off. The eye is able to see in dim light or bright light, but it cannot see objects when light is absent. The eye changes light rays into electrical signals then sends them to the brain, which interprets these electrical signals as visual images.
The eye is set in a protective cone-shaped cavity in the skull called the orbit or socket and measures approximately one inch in diameter. The orbit is surrounded by layers of soft, fatty tissue which protect the eye and enable it to turn easily. Six muscles regulate the motion of the eye. Among the more important parts of the human eye are the iris, cornea, lens, retina, conjunctiva, macula, and the optic nerve.
The cornea is sometimes referred to as the window of the eye. It provides most of the focusing power when light enters your eye. The cornea is composed of 5 layers of tissue. The outer layer (the epithelium) is the eye’s protective layer. This layer is made up of highly regenerative cells that have the ability to grow back within 3 days, and therefore, allow for fast healing of superficial injuries. Most of the inner layers provide strength to the eye. The laser vision correction procedure is performed on this part of the eye.
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 to become thinner or thicker as necessary. Between the ages of 40 and 50, the lens becomes less flexible and presbyopia sets in. As people reach their 60’s or 70’s, the lens sometimes becomes cloudy and hard (cataract formation), preventing light from entering the eye.
The pupil is the ‘black circle’ that you see in people’s eyes. The primary function of the pupil is to control the amount of light entering the eye. When you are in a bright environment, the pupil becomes smaller to allow less light through. When it is dark, the pupil expands to allow more light to reach the back of the eye.
This is the colored part you see in people’s eyes (i.e. blue/green/brown/hazel). 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.
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 may develop small clumps known as floaters, which are more common in nearsighted people than in the rest of the population.
The optic nerve carries images from the retina to the brain.
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. When your vision is perfect, the light rays coming into your eye focus precisely on this part of the eye.
This is the ‘white part’ that we see in people’s eyes. The sclera’s purpose is to provide structure, strength and protection to the eye.