Eyes are very complex organs, and their structure is highly specialized. Even though humans can pretty much see all of the way, the details of a person’s eyes are extremely sensitive. When you look into someone’s eyes, you can barely distinguish individual hairs, or even the location of a smile or frown. If you had two eyes open to your right eye, you could hardly tell that it was a man’s eyes and you would have been able to tell it was a woman’s eyes (if you could see at all). In this article we’ll be looking at a fairly common phenomenon: double vision.
Double vision occurs when the top half of one eye does not actually focus on the same place as the bottom half of the other eye, or vice versa. (Arabic for “double-folded”; as in “to turn toward” or “forbear to see”.) In vertebrates, only the major part of the eyeball is affected, while in lower animals, including jellyfish and insects, only a portion of the eyeball is affected. “Double-folded eyeball” it refers here. Thus, we find “orbitary eyeballs” in all vertebrates, and “ecological eyeballs” in crustaceans and the various fish species.
The second part of the eyeball is known as the “oculars”. It consists of the white middle chamber and the four pairs of bony casula. In humans, the optic nerve extends from the middle eye through the middle ear, the retina, and to the back of the head. The portion of the eye directly below the iris (the colored portion of the eye) is called the “refractive membrane”. The portion of the eye above the iris is called the cornea.
The third component of an eye, which has the largest functions in vision, is called the “orbital rim”. It is usually thick, similar to the epithelium, and surrounds the pupil. The iris determines whether or not the pupil is closed. The portion of the eyeball above the rim of the iris is called the iris. The pupil is the dark-colored area that contains the pupil.
The fourth component of an eye, which is the largest in number of its components, is called the “orbicularis”. This refers to the muscle used for raising and lowering the eyelid. It also helps in opening and closing the pupil. The upper lid is called the hypoid. The lower lid is called the inflatable eyelid.
The fifth component of our eyes, the “conjunctiva” is the innermost of all the organs. It consists of two cavities, the upper one containing the nerve fibers and the inner one housing the sweat glands. The conjunctiva is directly related to the eyes. The major function of the conjunctiva is to prevent tears from flowing backwards. When tears flow backwards, it blocks the nerve fibers located along the top of the eyelid and causes itching sensation on the eyelids.