Anatomy of the Eye
Guardion Health Sciences
In spite of how much we use our eyes in day to day life, most people do not have a good grasp on the anatomy of the eye nor do they understand how the optical system works.
An abridged explanation is that light passes through the front of the eye and is focused on the back of the eye, where it is converted into signals that are transmitted to the brain. Critical components of the eye are responsible for controlling how much light is let into the eye and others are responsible for focusing on objects at different distances.
The cornea is the clear front surface of the eye that allows light to enter and helps focus this light on the back of the eye. The cornea is located directly in front of the iris and is so transparent that you may not be able to see it.
The sclera is the white part of the eye surrounding the cornea. It makes up more than 80 percent of the eyeball’s surface area. It helps to maintain the shape of the eyeball and protect the eye from damage due to external trauma.
The iris is the colored part of the eye with an adjustable circular opening in the center called the pupil. Together, the iris and pupil help to regulate the amount of light that enters the eye. The pupil functions like the aperture of a camera. If there is too much light, the pupil involuntarily shrinks to let less light in; if there is not enough light, the pupil widens to allow more light in.
The lens plays a critical role in focusing light rays onto the retina and forming sharp images. The transparent structure sits behind the iris.
The lens has the remarkable ability to adjust very quickly to focus on objects at different distances. The shape of the lens must change in order to form a sharp image.
The lens is held in place by the ciliary muscles. The muscles contract and relax to help change the shape of the lens to focus on objects at varying distances. This process is known as accommodation.
The vitreous chamber or vitreous body is located behind the lens and in front of the optic nerve. It is filled with vitreous humour, a clear, jelly-like substance that helps maintain the shape of the eyeball.
The retina is the thin layer of light-sensitive tissue lining the inner surface of the back of the eyeball. It contains two types of special cells called photoreceptors. Rods detect motion, function well in low lighting conditions and provide black and white vision. Cones provide color vision and central vision, and function well in medium and bright lighting conditions. At the center of the retina is the macula, where the cones are concentrated.
These photoreceptor cells convert the light that is focused on the retina into electrical impulses that are transmitted to the brain.
The optic nerve is a bundle of approximately 1 million nerve fibers that transmit the electrical impulses formed by the retina to the visual cortex of the brain. It is made up of ganglionic cells or nerve cells. The nerve begins at the optic disk, a small structure where the ganglion cell output fibers (called axons) converge and leave the eye.
For more information about the anatomy of the eye and the problems that lead to glaucoma, age-related macular degeneration and other sight-stealing diseases, please contact Guardion Health Sciences today.