Myopia
Jacob M. Stanley
Mitchell Community College
Abstract
Myopia is a condition in which visual images come into focus in front of the retina of the eye. This condition causes objects at a distance to appear blurry, while objects nearby are seen clearly. If not severe, myopia can be treated with contacts or glasses. Other treatments for myopia include photoreactive keratectomy (PRK), LASIK, and orthokeratology. Degenerative myopia is a quick progression of myopia and leads to complete loss of vision. The treatment for degenerative myopia is a combination of medication and laser surgery.
Keywords: Degenerative Myopia, LASIK, Myopia, Orthokeratology, Photorefractive Keratectomy
Myopia
Myopia occurs if the eye is too long, or if the cornea
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has too much curvature. It is a condition in which close objects are seen clearly, but objects farther away appear blurred. To obtain clear vision, the eye must properly focus an image on the retina. In myopia, the image is focused in front of the retina because the cornea or lens curvature is too strong or the eye is too long. Myopia affects about thirty percent of the United States and increasing. There is some evidence showing that myopia may be inherited, or may be influenced by the visual stress of too much close work (Fredrick 2002). Generally, nearsightedness first occurs in school-age children. Because the eye continues to grow during childhood, it typically progresses until about age 20. However, nearsightedness may also develop in adults due to visual stress or health conditions such as diabetes. Common sign of nearsightedness is difficulty with the clarity of distant objects like a movie or TV screen or the chalkboard in school. Comprehensive optometric examination will include testing for nearsightedness (AOA 2015). An optometrist can prescribe eyeglasses or contact lenses that correct nearsightedness by bending the visual images that enter the eyes, focusing the images correctly at the back of the eye. Depending on the amount of nearsightedness, you may only need to wear glasses or contact lenses for activities, such as watching a movie or driving a car. For someone who is extremely nearsighted, they may need to be worn all the time. Cause of Myopia There is no known cause for the development of myopia. It is believed that a person is at higher risk if: one or both parents are nearsighted, or if the person spends too much time doing intense visual tasks (reading, working at the computer). Multiple studies show that children with more outside activities everyday has less myopia than children that spend their time inside doing more close work. Treatment Nonsurgical treatment. If the myopia is severe glasses or contacts must be worn at all times. If myopia is not severe glasses and contacts only have to be worn when needed for very clear distance vision (Driving, seeing the whiteboard, or watching a movie). Orthokeratology- non-surgical procedure where you wear a special rigid gas permeable contact lenses at night that reshape the cornea while the person sleeps. When the person wakes in the morning the cornea temporarily retains the new shape so you can see clearly during the day without glasses or contact lenses (Bailey). Orthokeratology. Overnight orthokeratology works to correct myopia by flattening the cornea through a mechanism of central epithelial thinning. The corneal periphery becomes thicker, thereby enhancing the peripheral corneal curvature. Good vision is possible by 1 week, stabilizing by 1 month. Treatment effects appear to be transient unless retainer lenses are worn every 1-2 nights to maintain the flattening effect. Refractive Surgery PRK (photorefractive keratectomy) is a type of surgery where a laser removes a layer of corneal tissue, which flattens the cornea and allows light rays to focus more accurately on the cornea. PRK was the first type of laser eye surgery for correction. Recovery time is longer than with LASIK. Offers some advantages over LASIK. LASIK is the most common refractive procedure. A thin flap is created on the surface of the cornea, a laser removes some corneal tissue, and the flap is returned to its original position (Boxer Wachler). In PRK, the eye surgeon does not create a flap of corneal tissue. Instead, the outer layer of the cornea is removed to expose an area for a laser to reshape. This makes PRK a better choice for people whose eyes meet certain criteria, such as having thin corneas or chronically dry eyes. During this recovery time, a PRK patient is given prescription eye drops (antibiotic and anti-inflammatory drops) to promote healing and to reduce discomfort after eye surgery. The drops are normally prescribed for several months following surgery. PRK patients can expect it to take one to three days for the discomfort, blurring and other post-surgical effects to subside, and it will take up to six months for vision to reach absolute peak acuity and clarity. LASIK recovery is much faster. Discomfort following LASIK surgery is usually mild and short In LASIK, an eye surgeon makes an incision (with either a laser or a blade) in the cornea to create a flap of tissue. The flap of tissue is lifted so the laser can be applied to reshape the inner layers of the cornea. A computer-controlled surgical laser carefully reshapes the layers of the cornea to repair imperfections in curvature that lead to distorted vision. Corneal flap is then put back in place and heals over the reshaped part of the cornea in a few days. term. While most patients report seeing normally within several hours after the procedure, their vision continues to improve gradually for several months before reaching peak quality. Pathological Myopia Pathological myopia is a malignant or pathological disease.
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
2011). Treatments. Laser photocoagulation uses heat from a thermal laser to destroy abnormal blood vessels. Unfortunately, it also damages healthy tissues in the retina and its light-sensitive cells. The result is some immediate, permanent vision loss. Visudyne (verteporfin for injection), also known as photodynamic therapy (PDT), is the first clinically proven therapy to treat pathological myopia.
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...
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