One of the things we make sure we get from our diet is Vitamin A because we know that it has to do with keeping our eyes healthy. Not only does this vitamin remove the threat of developing vision problems, but it also plays a direct role in creating the images you see. Without this one thing, the human eye is not capable of processing light into concrete and tangible pictures. In addition, getting the right amounts of this vitamin translates to fine-tuning the clearness of human vision.
There are many precursors of vitamin A. Carotenoids, such as beta carotene, are pro-vitamin A that are abundant in plant sources, for example, carrots and sweet potatoes. Retinol, the form we get from most animal sources, is the same form of the vitamin present in our body, and thus called preformed vitamin A. When the human body digests and absorbs any of these precursors, the liver converts them into many other forms for use by specific body parts. These forms are products of metabolism with some differences in their molecular structures but all collectively known as vitamin A. One form called retinal is delivered to the eyes where it is incorporated into the proteins that make up the retina.
Whenever we open our eyes the particles of light around us are interpreted by our brain. The cornea, the transparent outermost layer of the human eye, manages the direction and speed of the light coming in together with the lens. The pupil is the opening to the inner part of the eye, and the iris controls the amount of light that enters by changing the size and diameter of the pupil. When the light hits the retina, it is processed by cells capable of absorbing or reflecting each light particle. The images that we see are products of processed light particles.
A process called phototransduction takes place in the nerve cells inside the retina. In well-lit environments with high light levels typical in the morning, neurons called rod cells to change light particles into electrical signals delivered to the brain to produce visual representation. At night cone cells take charge of this process since they are more sensitive to light particles. Both neurons consist of proteins that manage the concentrations of retinal, the vitamin A in the retina. By doing so, each particle is either absorbed or reflected to create color at daytime or manage intensity in low-light environments.
Cells called epithelium that protects the eye from the outside environment make up the exposed part of the cornea. Epithelial tissues in the human eye need maintenance to avoid dryness that may give rise to rough dead cells, a major cause of many eye problems including the inability of the eye to produce tears. One form of Vitamin A called retinoic acid nourishes these tissues and its absence results in damages to the epithelium.
Little do we know that Vitamin A plays such a major part in the human body?