There is a very common problem which affects the eyes called astigmatism making it very difficult for people to see clearly and the vision becomes blurry. This causes an inability on the eyes to focus on general things from close up and from a distance; therefore, a person’s vision would not be able to distinguish at a very precise look.
There are two types of astigmatism: Regular, also known as “toric curvature” and it’s caused by the optical shape that arises from either the cornea or crystalline lens. This problem has been treated with the help of eyeglasses or toric lenses. The second type which is the irregular makes people see double or distorted images. They can result from a previous condition as keratoconus or refractive surgery; unfortunately, it can only be treated by the use of contact lenses other than surgery.
According to the National Institute of Health, a major defect of the eye that causes astigmatism has to do with the eye’s cornea. The cornea is the most anterior layer of the eyes that is clear and covers the front of it. Its main function is to transmit light in...
Optometrists have accepted vision therapy, which is a medical treatment for optical muscle disabilities, as a feasible treatment used for eye related problems; claiming the treatment can strengthen vision and give the patient the opportunity to understand visuals quicker and clearer (Press). Vision therapy originated in the 1950s and over the past 25 years, has gained popularity, mainly because of new technological innovations in the field of treatment. Generally, vision therapy is prescribed as a measure mainly for people between the ages of 3 and 18. With the results from a comprehensive series of eye tests, the optometrist can work with the patient using special instruments—prisms, filters, occluders, and eye lenses—and strengthen the eye muscles, thus improving sight. According to optometrists in favor of vision therapy, these methods of treatment using these instruments function as safer routes to repair eye disabilities. Although vision therapy can yield favorable results, the practice as a treatment for innate eye disabilities has been in hot debate lately; as it can exceed $8000 and insurance companies do not cover the treatment. For decades, insurance companies have refused to accept vision therapy as a legitimate method for repairing eyesight (Boink). Concomitant with lack of insurance, the cost for a full treatment can exceed $8000, and doctors cannot guarantee a successful outcome. Recently, parents of children with eye related disabilities, such as amblyopia (lazy eye) and strabismus (cross-eye), and doctors have attempted to cooperate with public schools to allow families access to school-funded doctors to practice vision therapy. With a tight budget, most schools cannot afford to supply vision therapy, and a...
With no treatment needed, glaucoma is a leading cause of blindness in the United States, while simultaneously being the number one leading cause in Africa (Glaucoma Research Foundation). According to the American Optometric Association, “Glaucoma is a group of eye diseases causing optic nerve damage. The optic nerve carries images from the retina, which is the specialized light sensing tissue, to the brain so we can see.” They go on to say that when dealing with glaucoma, one’s eye pressure plays a vital role in damaging the delicate nerve fibers of the optic nerve. “When a significant number of nerve fibers are damaged, blind spots develop in the field of vision. Once nerve damage and visual loss occur, it is permanent.” The National Institute of Health states that due to shallower anterior chamber depths, this defect hurts the lives of people mostly from East Asian descent. The Foundation continues to say that blacks are among the people who are three times more likely to have glaucoma while woman in general are two times more likely to developing angle closure glaucoma.
Processing capacity is a very broad and flexible category according to many researchers. In fact, the quote above mentioned suggests that we often fail to notice things that happen just in front of us (unexpected events that are often salient) either because we were completely absorbed by something else or because we had so many things to do at the same time that we couldn’t pay attention to it. We have all at least once failed to see a friend who was waving at us while eating in the cafeteria or walking in a crowded street. The primary question that we should ask ourselves is: how many things can we attend at the same time? The truth is that we didn’t perceive this friend because of a phenomenon called “inattentional blindness”. The problem is that the richness of our visual experience leads us to believe that our visual representation will include and preserve the same amount of detail (Levin et al 2000). In this paper we’ll see the different theories of inattentional blindness, and the classical theories demonstrating this paradigm.
Myopia is defined as nearsightedness, which exists when the refractive elements of the eye (cornea and lens) place the image in front of the retina. The myopic condition is common in infants but generally levels off to normal vision as the infant ages (Vander & Gault, 1998). Myopia occurs in about 25% of the adult U.S. population. Many adults use corrective lenses or contacts to correct their myopic vision to 20/20 vision (Drexler et al., 1998). Many people find contacts or glasses hindering in their personal and/or professional lifestyle. For example, military pilots cannot wear glasses while flying and some firemen may find glasses too dangerous to wear during a rescue attempt. There is refractive surgery available to correct myopic eyes, like Photorefractive Keratectomy (PRK). Why do people have myopia, what can be done to correct myopia, and what are the results of corrective surgical procedures? These are a few questions that will be addressed and analyzed.
It is a rare condition that affects 2 % of Americans. Signs of pathological myopia include: Bending or distortion of straight lines, altered color perception, reduced contrast sensitivity, and increasing gloss of central vision. It is a quick severe progression of myopia and loss of vision is the end result. There is an increased risk of retinal detachment and other degenerative changes in the back of the eye (bleeding from abnormal blood vessel growth). If any of these things occur the risk of cataracts could increase. Treatment calls for a combination of a drug and a laser procedure called photodynamic therapy. It is reported to be the seventh ranking cause of legal blindness in the United States of America the fourth ranking cause in Hong Kong and the second in parts of China and Japan this form of myopia frequently progresses in adult life, with small intermittent steps of elongation being observable at any age. The adult progression appears to be due to the stretching of the walls of the eye. Genetically weak elements of the scleral wall are prone to thinning and stretching. One of the major forces at work in this stretching process appears to be the normal intra-ocular pressure (Ward
Myopia and hyperopia are two such conditions. Myopia is more commonly referred to as nearsightedness and leaves the person with the ability to see objects that are close up clearly, but those that are far away are out of focus. Hyperopia, in contrast, involve the inability to see objects that are near clearly and is often referred to as farsightedness. Objects that are far away, however, can easily be seen.
Eyes are the ‘organ of sight or vision; the visual sense; the sense of seeing’ (Biology-Online). The eye is an organ that detects light and sends signals along the optic nerve to the brain. The eye allows for light recognition and the ability to differentiate between colors, and light and dark. The eye is approximately 2.54 cm wide, 2.54 cm deep and 2.2 cm tall. The human eye has around 200-degree viewing angle and can see and detect more than 10 million colors and shades. This essay is going to look at ways of seeing. The possible problems with eyesight, and eyes of various kinds. It is one of the most rare problems today that is affecting people, all over the world. Around the world an estimate of 4 in 10 people have perfect vision/sight (BBC). The population of the world right now
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.
There are several types of amblyopia. Researchers must be aware of the various types of amblyopia because the effects for each are not always consistent. Strabismic amblyopia is caused when the two eyes are out of alignment due to weak musculature. Anisometropic amblyopia is a result of a large difference in refractive power of an individual's eyes. Another form of amblyopia results when visual information does not reach the retina. This is called stimulus deprivation amblyopia. Meridional amblyopia is a result of the diffused images caused by astigmatism. Researchers often discover that there are differences between groups of amblyopes based on type. For example, Levi and his colleagues (1994) discovered differences in vernier acuity between anisomet...
middle of paper ... ...137-137. Human Perception and Performance, 15(3): 448-456. Eriksen, C. W. & St. James, J. D. (1986). Visual attention within and around the field of focal attention: A zoom lens model.
Open-angle glaucoma - With this form of glaucoma, the loss of vision occurs so gradually it is rarely noticed. However, as eye damage increases, you will eventually find that you have lost a lot of areas of your peripheral vision, especially the field of vision near your nose. As larger areas of your peripheral vision fade, you may develop tunnel vision -- vision that has narrowed so you see only what is directly in front of you. If glaucoma is not treated, even this narrowed vision disappears into blindness. Once gone, areas of lost vision canno...
Our attention is very selective when it comes to getting information from our environment. We could be looking at everything within our environment and miss changes that occur while looking. According to Rensink, O’Regan and Clark (1997), attention is a key factor, meaning when our attention is focused on the area of change then change can be detected. When we fail to detect change, it can result in change blindness. In support of this idea, Simons and Levin (1998) suggest that change blindness occurs if there is a lack of “precise” visual representation of their surroundings. In other words, a person can be looking at an object and not fully notice a change.
Robert, a 65 year-old male, has trouble reading fine detail, especially out of his central vision. He complains that his vision is blurred and that it is harder to see while operating a motor vehicle. In addition, sometimes objects appear wavy or crooked, which impairs his vision. His worst symptoms were that he occasionally lost the ability to distinguish between the features of familiar faces and he had a localized blind spot. Robert is not alone; many people suffer from symptoms related to loss and distortion of the visual field. He suffers from macular degeneration, the leading cause of decreased vision loss in the United States, especially for people over the age of 50 (Philippi, 2000).
Visual Processing Disorder, also known as Perceptual Disorder, is defined as “a hindered ability to make sense of information’s taken in through the eyes.” (National Center for Learning Disabilities (NCLD) 1999) http://www.ldonline.org/article/6390/ This does not mean that a person has problems with their sight or their vision, it just means that their brain has a tougher time interpreting and processing what they see visually. A common area affected is spatial relation. This is the “position of objects in space as well as the ability to accurately perceive objects in space with reference to other objects.” (National Center for Learning Disabilities (NCLD) 1999) http://www.ldonline.org/article/6390/. This can make reading and mathematics difficult to comprehend and understand, since both subjects deal with lots of symbols like numbers and punctuation marks. Often, however, most problems occur within math. In order to succeed in math, a person with this learning disorder must learn to associate the digit or sign by making a common relationship between them.
...he cornea is deformed so that its surface is oval instead of spherical. Light rays are distorted at the entrance of the eye. This produces a blurred image and is known as astigmatism. To correct it, glasses are given a nonspherical or cylindrical curvature. Cross-eyes and walleyes are produced when both eyes do not work together because of weakness of the eye muscles.