The eye has external and internal parts, and they are mentioned as follows:
Sclera: A noticeable white part. Its skin is thick and protects the inner portions.
The conjunctiva: It is a squamous epithelium that lines the sclera. It lubricates the eyes by secreting mucus and tears.
The cornea: The cornea the transparent part of the eye that serves as covering for the iris and pupil in front of the eye.
The iris: It is the visible and pigmented part of the eye. The principal role of the iris is to adjust the size of the pupil according to the light source.
The pupil: It is the opening in the iris, which lets the light into the retina.
Internal components of the eye include:
Lens: It is the eye’s clear biconvex lens. Ligaments are tough elastic tissues that bind the body parts together. When light hits the retina, the cornea and lens bend and refract light and accumulate it on the retina. From this point, the retina receives the light rays and then sends the image to the brain.
Retina: It is the innermost layer in the eye, and it is light-sensitive. It turns images into electrical nerve impulses for the brain to perceive. The photoreceptors (light-sensing) and nerve (ganglion) cells are present in the retina along with two types of receptor cells: cones and rods. These rhodopsin-producing cells convert light energy (photons) into neural tissue electric energy (photochemical reaction). Rod controls peripheral visions. That is why it sustains high light sensitivity. Cones require lots of light to function but allow for fine detail recognition (direct vision) and color appreciation. The macula contains most of the cones responsible for sharp vision. Retina abuts choroid, but not perfectly. It can detach here due to retinal diseases.
The optic nerve: It is placed behind the eyes. The optic nerves carry the retina’s nerve Receptors in the skin send stimuli to the brain for comprehension and processing of information.
Aqueous humor: Aqueous humor is the liquid fluid that is present between the cornea and the lens and nourishes the parts of the eye that are not vascularized.
Vitreous humor: It is defined as the translucent, jelly-like substance present between the lens and the retina in the eyeball. It is 99 percent water, collagen, proteins, etc. The vitreous humor protects the eyes and keeps their spherical shape.
Mechanism of working of the eye
The eye carries the information to the visual tract and optic nerve chiasm and travels it through several parts of the brain end lobe. Moreover, the end lobe is the area where the image formation takes the place of the visuals and see of the outer world. Each one of these is the essential element of visual analyzer as well as a visual system. The two eyes are responsible for creating 3D vision called stereoscopic vision.
The right retinal side of the eye transmits the “right part” of the object or image to the right brain through the optic nerve, and the left retinal side transmits the “left part” of the object to the left brain. Brain amalgamates these two elements of the brain to create a fresh visual image. Given that each eye receives its own picture when the joint movements of the right and left eyes are disrupted, binocular vision may be affected as well. Thus, in simple words, the eyes have double vision or start noticing several pictures altogether.
Interesting facts about the eyes
Newborn babies can see only black and white images and detect certain objects in red against a grey background. The reason behind why they are unable to see some specific colors is the weakness of their photoreceptors cells. The cones in the eyes, or photoreceptors cells are so weak that they have some specific colors in the range or even detect their presence. However, these cells strengthen shortly.
Babies can differentiate between red and green just after the weeks after birth. They can also detect the difference between blue and yellow.
Furthermore, the eye muscles are one of the fastest muscles in the human body. Even though there are several muscles present in our eyes. Therefore, fast-moving parts are responsible for moving eyes in different directions.
Everyone had brown eyes at first. A genetic mutation gave birth to the first blue-eyed person between 6000 and 10,000 years ago, according to a study in 2008. This study also describes the mutation of the OCA2 gene, essentially decreases the chances of producing brown eyes and thus dilutes the color to blue.