The lens is a clear structure located just behind the pupil.
The human eye is a remarkable organ. It automatically adjusts due to changing lighting conditions and adapts its focus for images at differing distances. The images strike the back wall of the organ and are converted into electrical impulses that are transferred to the brain. One of the most important components of this process is the lens.
Function
The lens is a circular, concave, transparent structure located at the front of the eye. A thin, transparent coat called the cornea protects the lens from harm, cushioning the delicate tissue within the fluid-filled anterior chamber. As an image enters the eye in the form of light waves, the lens flips the image and determines where it lands in relation to the back of the eye.
The Necessity of the Iris
The iris will be familiar to you as the colored component of the eye. It is actually a muscle surrounding the lens that contracts and expands to adjust the lens' shape. When a human is looking at a distant object, the iris contracts and compresses the lens, making it thicker. However, when a human is looking at a nearby object, the iris expands and stretches the lens, making it thinner. This is due to the nature of light beams entering the eye from varying distances. The adjustment of the lens ensures that the inverted images will land on the back of the eye.
Lens Development
The human eye begins development two weeks after conception. All major eye structures, including the lens, form over the next four weeks. The eye continues to develop over the course of the next seven months, and the baby can see once the eye is connected to the brain via the optic nerve. This period of development is precarious, as the eye is particularly vulnerable to infection or mutation.
Lens Deterioration
In both humans and animals, the lens deteriorates with age. Before the age of 40, the lens is still flexible and quick to adjust for objects at differing distances. After the age of 40, the lens begins to harden, making the eye take longer to focus. The iris must work harder to stretch and compress the lens, causing the eyes to feel tired and sore with prolonged use. The lens can also gradually cloud over the course of time, making images fuzzy and colors less vivid. A cataract is the clouding of the lenses.
Lens Surgery
Cataracts eventually can rob you of our sight. For those who lived before the 1900s, blindness due to cataracts was common. However, with the advent of advanced eye surgery, cloudy lenses can be replaced with plastic lenses in a few minutes. The procedure requires only local anesthetic, and the patient is able to return home after completion. Some pet owners have this procedure performed on their pets, as well.
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