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physics of the eye
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Protections of the eye:
The human eye is one of the most important things to a person and thus has many forms of protection.
The eyelid protects the eye in three different ways: the eyelashes, the glands, and the movement of the eyelids.
The eyelashes are beneficial in keeping dust and debris out of the eye. Touching the lashes will trigger the reflexive blinking mechanism.
There are many different glands that are located in the eye. The Zeis gland is a gland that secretes oil. An infection in this gland results in a stye. A second gland, the Meibomian gland, are large oil secreting glands located in the lid of the eye and play a part in producing the oily outer layer of tears. This oily layer prevents the evaporation of tears. Also contributing to the make up of tears are the aqueous and mucous producing glands.
Eyelids protect the eye mainly by their rapid rate at which they cover the eye. Even though blinking interrupts the line of vision, the illusion of sight continues while the eye is briefly closed.
The Cornea:
The cornea is the front part of the eye and is a transparent tissue that lacks blood vessels and covers the iris and pupil. The cornea allows light rays to permeate and bends the light enough to allow for focusing of the eye.
The cornea contains five different layers:
* the epithelium
This is the outermost layer of the cornea. The cells of the layer offer a smooth surface that serves the tear layer well.
* Bowman's membrane
This is the main part of the cornea. It is a tough layer of transparent tissue that has no cells. It is made up of mostly collagen material.
* the stroma
This layer has other layers in it of tissue called lamellae which go through the e...
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...is focused on the retina. The image is actually seen on the retina upside down, and is reversed when it is sent to the brain. Recall that the left side of the brain controls the right side of the body, and in remembering this, the fact that the left half of the visual field in each eye is sent to the right half of the brain.
Although an eye is likened to a camera, "[t]he one major difference is that the focus of the eye is altered by changing the focal length (or power, P=1/f) of the lens, rather than by changing the distance between the lens and the retina." (www.dur.ac.uk/r.g.bower/OpticsI/optlec/node34.html)
Works Cited:
Cassel, Gary, et al. The Eye Book: A Complete Guide to Eye Disorders and Health. The John Hopkins University Press: Baltimore & London. 1998. (pp. 3-15)
D'Alonzo, Dr. T.L. Your Eyes! Avanti Publishing: Pennsylvania. 1991. (pp. 15-54)
The second layer of the skin is called the dermis and is also known as the middle layer. The dermis is what holds the body together. The dermis has layers to it as well as the epidermis. There are two layers to the dermis, the papillary layer and the reticular layer. The cells of the dermis are fibroblast, macrophages, mast cells, and scattered white blood cells (wbc’s). the dermis is richly supplied with nerve fibers and BV;s. dermal BV’s is also a part of the integumentary system, dermal BV,s have converging and diverging vessels that ar...
Regarding to the ocular examination, the patient's visual acuity without optical correction (spectacle) was good 20/20 in both eyes. IOP measurements was 18 mmHg on the right eye and 16 mmHg in the left eye. The pupil was equal, round and reactive to light with no afferent pupillary defect in both eyes. In extarocular movement test, there was limited downward gaze with
For an eye to focus correctly on an object, it must be placed in a certain position in front of the eye. The primary focal point is the point along the optical axis where an object can be placed for parallel rays to come from the lens. The secondary focal point is the point along the optical axis where in coming parallel rays are brought into focus. The primary focal point has the object's image at infinity, where as the secondary focal point has the object at infinity. For people who have myopic eyes, the secondary focal point is anterior to the retina in the vitreous. Thus, the object must be moved forward from infinity, in order to be focused on the retina. The far point is determined by the object's distance where light rays focus on the retina while the eye is not accommodating. The far point in the myopic eye is between the cornea and infinity. The near point is determined by which an object will be in focus on the retina when the eye is accommodating. Thus, moving an object closer will cause the perception of the object to blur. The measurement of these refractive errors are in standard units called diopters (D). A diopter is the reciprocal of a distance of the far point in meters (Vander & Gault, 1998). The myopic condition manipulates these variables in order to ultimately make a nearsighted individual.
The endothelium is a cell layer that is lined on the interior surface of lymphatic vessels and blood vessels, which are made up of endothelial cells (Dorland, 2012).
Sight helps us navigate the world around us more than any of our other senses. In a fraction of a second, our eyes work with our brains to tell us the size, shape, and texture of an object. They also tell us how close it is and if it’s still or moving. The structures of our eyes are incredibly complex, despite how small they are compared to the rest of our organs. The human eyes are extremely delicate. The visible part of the eye is protected by the eyelids and eyelashes, which keep out dirt, dust, and harmful bright light.
Life revolves around being able to see things. Although individuals who are blind can lead a full and happy life, someone with excellent vision who suddenly loses theirs or notices a decrease in their visual acuity over time may find it difficult to adapt. Thankfully, with the help of an optometrist, individuals can actively work to preserve their vision for as long as possible. Phoenix Eye Care must be a priority for all, as advanced technology allows threats to the eyes to be detected as the earliest stage. The right treatment can help to slow or stop the progression before major issues develop. For this reason, every individual needs to undergo routine eye exams.
The four main components of the eye that are responsible for producing an image are the cornea, lens, ciliary muscles and retina. Incoming light rays first encounter the cornea. The bulging shape of the cornea causes it to refract light similar to a convex lens. Because of the great difference in optical density between the air and the corneal material and because of the shape of the cornea, most of the refraction to incoming light rays takes place here. Light rays then pass through the pupil, and then onto the lens. A small amount of additional refraction takes place here as the light rays are "fine tuned" so that they focus on the retina.
Fluid circulating inside the front portion of the eye is produced by a structure called the ciliary body, which is located behind the iris. This fluid moves through the opening of the pupil, passes into the space between the iris and the cornea, and drains out of the eye through a tissue called the angle. With glaucoma, the passing of fluid through the angle is either reduced or suddenly stops, and amounts of fluid inside the eye increase. This high fluid pressure hurts the nerve fibers and the eye's optic nerve and causes blind spots. It may lead to blindness in some cases.
the cornea and the sclera. The cornea is what covers the iris, and is the
In 1802, philosopher William Paley called the eye a miracle of "design". Your eyes are responsible for 80 percent of all of the information that your brain receives. (Schleifer, 2014) But how did our eyes form? How are we able to see what we see? What allows us to see the colors we see? The eye is made up of many different complex parts that all work together to create images our brain can understand. The eye is made up of the front parts, or parts we can see, the interior parts, or parts we can’t see, the nerves which carry signals to our brain, and glands that protect our eyes. The eyes we have today have evolved over a long period of time and undergone many different changes, according to Charles Darwin, Richard Dawkins, and many other evolutionists. When all of the different parts of our eyes work together we are able to see a clear image that is produced from our brain.
There are three simple tissues namely, parenchyma, collenchyma, and sclerenchyma. Parenchyma is thought of as the ground tissue of an axis since it occurs in greatest abundance and is the tissue in which the vascular tissues are embedded. Parenchyma cells may be isodiametric in both the pith and the cortex, but are more mostly longitudinally elongated in the cortex. They have comparatively thin walls. Wall layers are continuously shaped regions. These simple pits usually occur opposite each other, forming pit-pairs in the walls of contiguous cells. Plasmodesmata (specialized strands of endoplasmic reticulum) form interconnections with the protoplasts of adjacent living cells through simple
The epithelium tissue helps protect the body. It lines the surface. Epithelial tissue has an apical surface which means it is lined with microvilli above tight junctions. There are four main types of epithelium tissues; squamous epithelial cells, Cuboidal epithelial cells, columnar epithelial cells and ciliated columnar cells. The squamous epithelium protects the linings in the body such as blood vessels and air sacs in the lungs. The cuboidal epithelium protects things such as the kidneys and glands as they can
The incredible thing about the human eye is that it can see objects to as far as 2 miles long.That’s almost 35 football fields! Let’s consider the mechanics of the eye. The eye is a clear ball with water-like fluids in there.You have the front of the eyeball which is translucent called the cornea. It’s extremely thin and its job is to protect the eye by refracting light that comes through. The next part of the eye is the pupil, which mostly everyone knows about.It is the black portion in your eye. Did you know that it gets its color from when light entering the eye is absorbed and it doesn’t leave the eye. You may also notice that when you’re looking at the pupil, you can see a different colored circle in them. This is called the iris, and it varies among everyone. Your actual eye color is determined by a pigment in the iris.The genes from your parents set a human’s eye color. The iris’s job is to widen or close depending on how bright or dark it is. If its bright and the sun is basically beaming down on you, the iris will adjust so your pupil will get smaller to only let a certain amount of light in. If you’re in the dark, your iris adjusts so your pupil will get bigger so a greater...
As further protection, the eyelids automatically close when an object suddenly moves close to the eye.Parts Of the EyeThe eye is made of 3 coats, or tunics. The outermost coat consists of the cornea and the sclera. The middle coat contains the main blood supply to the eye and consists of the choroid, the ciliary body, and the Iris. The innermost layer is the retina.Cornea and ScleraThe Sclera, or the white of the eye, is composed of tough fibrous tissue. On the exposed area of the eye the scleral surface is covered with a mucous membrane called the conjunctiva.