The eye is one of the most remarkable organs in the human body. It must adapt to ever-changing conditions to focus light that travels from various distances. When all structures in the eye function properly, the eye converts light to impulses that signal the brain to perceive an image.
Vision starts with rays of light that bounce off an object and enter the eye. The light enters through a clear layer of tissue called the cornea. As the primary element of focus, the cornea is a very important structure. The outer layer or epithelium protects the eye, while the inner layer allows light to pass.
Both the outer and inner corneal layers consist of transparent tissue. Shaped like a clear dome that covers the eye, the cornea is sometimes called the “window” of the eye. It refracts light or bends it as it passes through the pupil.
The pupil is a small, dark hole that is located in the middle of the iris, the component that determines eye color. The iris is designed like the aperture of a camera lens. It widens and narrows the pupil to control the amount of light the eye receives.
Behind the iris is a structure called the lens. It has the important task of focusing light rays onto the back of the eye, on a structure called the retina. The lens must make numerous, delicate adjustments on a continual basis to bring light into focus.
In children and young adults, the lens is a soft, supple and flexible structure. It can bring light into fine, sharp focus from various distances. In people over 40 years of age, however, the lens is much less pliable. This makes near-vision focus difficult, causing a condition called presbyopia. Most middle-aged people require corrective lenses to see objects up close.
The lens must constantly adjust the path of light to ensure proper focus on the retina. This thin tissue membrane serves as the back inner lining of the eye. It contains millions of photoreceptor cells called cones and rods.
These cells are named for their distinctive shapes. Cones are located in the macula, an area that lies in the center of the retina. They ensure that vision is clear, sharp, colorful and detailed. Rods are located near the edge of the retina. They enable peripheral vision to the sides of the eye and allow it to detect motion.
The eye’s photoreceptor cells convert light rays into electrical impulses, which the optic nerve sends to the brain. The brain reads the nerve signals to perceive sharp, detailed images in the mind.
The clear, gelatinous substance that fills the interior of the eyeball is called the vitreous body or vitreous humor. It is primarily a protective substance that removes unwanted debris in the eye’s field of vision.
The diverse and complex structures in the eye work together in much the same way that various camera components work together. Each structure has a unique role, and each is vital for providing clear, sharp vision. It’s iherb coupon code.