Our eyes are one of the most important tools we use to process the world around us. They allow us to interpret shapes, faces, colors, and depth without touching them—a critical evolutionary advantage. In fact, it is thought that the first animal to gain true imaging would have touched off an evolutionary “arms race”, as any species that didn’t have this special function would have died off quickly. Today, our Raleigh optometrists explain the different parts of the eye and how they work together to help us see.
Human eyesight: The basics
The eye translates the light that reflects off of things into electrical signals, which our brain reads as images. To do this, it enlists the help of 10 general components that all work together. The eye is protected and surrounded with motion-regulating muscles and layers of fatty tissue that further help us see.
The cornea is the outermost layer of the eye that is primarily responsible for focusing light. The cornea consists of 5 layers. The deeper layers exist mainly to strengthen the eye, and the outer layers act as a kind of “shield” to the elements. The outer layer of the cornea is often able to repair itself within a few days of suffering a minor injury; however, deeper corneal abrasions will require attention from your optometrist.
The pupil is the black circle in the center of the eye. Its primary function is to monitor and control the amount of light that comes into the eye. When there is a lot of light, the pupil contracts to keep the light from overwhelming the eye’s delicate sensors. When there is very little light, the pupil expands so it can soak up as much light as possible. This is why your pupils look very large in near-darkness.
The iris is the colored part of the eye, but it is far from purely cosmetic. The iris actually functions to adjust the size of the pupil. It has muscles that contract or expand, depending on the amount of light the pupil needs to process images.
The lens sits behind the pupil, and enables the eyes to focus on small details, like the words in a book. The lens is in a constant state of adjustment, as it becomes thinner or thicker to accommodate the input it receives. As people age, their lenses lose a lot of their elasticity, which often results in conditions such as cataracts wherein the lenses cannot adjust to their surroundings as well as they used to.
The vitreous humour is a transparent, gel-like substance that helps to keep the eyeball in its proper, circular shape. If you have ever seen a “floater”, or a tiny speck that floats in your field of vision, it is most likely pieces of the vitreous humor that have clumped together and cast shadows onto the retina. With age, the vitreous humor begins to shrink and can cause problems like retinal tears.
The retina is the area at the back of the eye that receives the refined, visual message from the front of the eye via the optic nerve. Once your retina receives a visual message, it transmits it to the brain using electrical signals.
The sclera is the scientific name for the “whites” of the eye. Its main function is to provide strength, structure, and protection for the eye. The sclera contains blood vessels, which is why the whites of your eyes can sometimes look pink or red if infected or irritated. The conditions of your sclera, therefore, can tell an eye doctor a lot about the state of your overall health.
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