The function of the eye is to observe our surrounding by taking in and transforming light into electric signals which can be decoded into images and interpreted by the brain.
The eye is surrounded in a tough covering called the sclera, also known as "the white of the eye". The sclera protects the eye and is transparent to allow light to pass through it. Humans have 6 extrinsic muscles around the eye to move the eye by some of the muscles contracting and other expanding. The eye is surrounded in fatty tissue to cushion the protect the eye from impact or damage.
Light first enters the eye through the cornea, a transparent cover that protects the pupil, the iris, and the anterior chamber. The aqueous is found behind the cornea and helps give the eye its spherical shape. The cornea roughly focuses the light, and then the light enters through the pupil, which is a dark circle in the center of the eye that allows light to pass through. The pupil is not technically a structure but instead is a hole to allow light into the eye. Surrounding the pupil is the iris, the colorful part of the eye. The 2 muscle layers of the iris constrict and expand to change the size of the pupil to control the amount of light entering the eye. Staying in a dark room causes the iris to constrict enlarging the pupil to allow more light in. But if you walk outside into the sunlight, the iris will quickly expand shrinking the pupil to prevent too much light entering the eye and damaging it.
After passing the pupil, the lens focuses the light by bending and altering the shape and angles of light rays to focus them properly. A condition where the lens turns cloudy is called cataract. Cataracts reduce the amount of light reaching the retina, but can be treated by removing the lens and replacing it with an artificial one. The lens is held in place by the suspensory ligaments that join with the smooth muscle containing ciliary body. The light passes through the vitreous humor that fills the center cavity of the eye which also helps the eye keep its shape as does the aqueous humor. Glaucoma is the condition where there is too much fluid pressure from the aqueous and vitreous humor in the eye, causing eye damage. The retina lines the back of the eye. The retina lies on top of the choroid layer, which is a network of blood that is used to bring oxygen and nourishments to the back of the eye. The tapetum lucidum is not found in the human eye but it helps animals in night vision since it can reflect light at very low intensity onto the retina. The retina is lined with photoreceptors that sense different types of wavelengths of light that is converted into electric signals and sent through the optic nerve to the brain.
Other dysfunctions of the eye are myopia (nearsightedness) or hyperopia (farsightedness). In myopia, the eyeballs are too long and the cornea is too curved; the image lands in front of the retina and allows the person to see near images but not far ones. In hyperopia, the opposite occurs. The eyeballs are too short and the cornea is not curved enough. The image lands behind the retina and the person won't be able to see things clearly when they are close, but can see objects clearly when they are further away.
No comments:
Post a Comment