Full version Keratoconus

Keratoconus

This print version free essay Keratoconus.

Category: Science

Autor: reviewessays 10 February 2011

Words: 1926 | Pages: 8

Keratoconus

Keratoconus is a disease of the eye that is common sometimes. This syndrome can affect many people who can have very serious problem. There are many different backgrounds of the keratoconus such as history, what is keratoconus, causes of the diseases, symptoms, signs and diagnosis, and other treatments.

Keratoconus was the first study by German oculist, Burchard Mauchart in a 1748, which he called staphyloma diaphnum. However, physician John Nottingham clearly described keratoconus as the cases of conical cornea and also he described several classical features of the diseases such as polyopia, weakness of the cornea, and difficulty matching corrective lenses to the patients vision. In 1859, a British surgeon named William Bowman to diagnose keratoconus used an ophthalmoscope to see the conical shape of the cornea. According to Wikipedia encyclopedia, Bowman also attempted to restore the vision by pulling on the iris with a fine hook inserted through the cornea and stretching the pupil into a vertical stenopeic slit like that of a cat. Bowman had a good success with that technique, as an example he restorted vision to an 18 year old woman who had previously been unable to count fingers at a distance of 8 inches (20cm). In 1888, the treatment of Keratoconus became one of the first practical applications of the newly invented contact lens, when the French physician Eugene Kalt manufactured a glass scleral shell, which improved vision by compressing the cornea into in more regular shape (Wikipidia 2). From that time, research of keratoconus has improved understanding of the disease and greatly expanded the choice of the treatment options.

Keratoconus is an eye condition named after the Greek Terms “kerato” which means cornea, and “conus” meaning cone, which also can be hearing a conical cornea (Wikipedia 1). There are three ecstatic corneal dystrophies such as Keratoconus, Kertoglobus, and Pellucid Marginal Corneal Degeneration. Out of three Keratoconus is more common. The cornea is normally a round or spherical shape, but with keratoconus the cornea blurs, distorts and assumes more of the cone shape. It is a disease that leads to the stromal thinning and the bowing forward of the affected cornea which may result in irregular myopic astigmatism, distortion of vision, increased sensitivity to glare and light and an associated reduction in visual acuity. It usually happens around puberty and then it becomes worse during the teens and the mid-20’s and becomes stable by the late 20’s. According to Angeles Vision Clinic article, “Over 90% of patients have involvement of both eyes, though it is not unusual for there to be asymmetric changes, with one eye being more involved than the other.” However, each eye can be affected differently which can result in dramatic decrease in the ability to see clearly even with corrective lenses.

In a fact, about 1/2000 people will develop keratoconus. Most people will have a mild or moderate form of the disease. Less than 10% of keratoconics will develop the most severe form. However, many people have diagnosed in their mid to late thirties; this is usually a more mild form of the diseases. It's very common for one eye to precede faster than the other is, then it changes dramatically over a period of month.

The sign and symptom of kerataconus can be difficult to detect, because it comes on slowly. Nearsightedness and astigmatism also accompany this decease, so patient may have destroyed and blurred vision. According to the Wikipedia article, Keratoconus can be identified by changes in behavior. People suddenly have problems with steps or changes of surface and they don't like go out in the sunshine. That's why we can notice problem with glare and light sensitivity. Keratoconus patients often have prescription changes each time they visit their eye care practitioner. It’s not usual to have a delayed diagnosis of keratoconus if the practitioner is not familiar with the early stage symptoms of the decease. Kerataconus patients also often report multiple images or ghosting of images, which is known as monocular polyopia, and often relate a history of frequent refractive correction changes without much improvement in visual acuity. Instead of seeing just one point, a person with keratoconus sees many images of the point that is spread out in a chaotic pattern. Patients may also report irritating symptoms such as intolerance to glare, photophobia (light sensitivity) and recurrent foreign body sensations.

There are more signs of Keratoconus than there are symptoms. The Wikipedia article says that the disease is usually bilateral, but may be quite Asymmetric. The corneal thinning and ectasia happens in three main parts: a nipple cone, where the cone is a small and centered on or near the center of the cornea; an oval cone, where the affected area is larger and usually centered infer temporally; and a globus cone, where the area of involvement covers most of the central cornea. The names of these signs are Vogt’s Striae, which is seen by deep stromal usually vertical stress lines at the apex of the cone. Munson’s sign is building forward of the inferior eyelid on down gaze. Fleischer ring is an epithelial iron deposition in a ring around the cone.

Keratoconus is caused by weakening of the cornea. It causes the outward flange and thinning of the cornea. According to an article by Keratoconus Inserts, the cause of the weakening is due to an imbalance of enzymes within the cornea itself that leads to high levels of damaging reactive species chemicals. There are different types of reactive species include super oxides, hydrogen peroxide, and nitric oxide. These free radicals can cause oxidative damage to the cornea. There are some genetic reasons explaining why the good enzymes do not functions properly. Non-genetic sources can also increase the reactive species such as ultraviolet light sun exposure, eye rubbing, poorly fit contact lenses, and chronic eye irritation. As a response from Keratoconus Inserts, “all patients with keratoconus has to protect their eyes by wearing100% UV blocking sunglasses with the wrap-around design which minimizes light coming in from the sides.” Keratoconus occurs in females slightly more than in males. One long-term study indicates a prevalence of 54.5diagnosescauses of keratoconus per100.000population. Keratoconus has been found with other medical disorders such as atopic disease, Down's syndrome, Ehlers-Danlos syndrome, and Marfan's syndrome.

Keratoconus has two main stages, which is mild (beginning stage), and severe (condition). In the early stages of keratoconus, eyeglasses or soft contact lenses may be used to correct the mild nearsightedness and astigmatism. But as the decease progresses and the cornea thins and changes shape even more, glasses or soft contact lenses will no longer correct your vision, so it will be a severe condition which you only can prescribe a "hard" or rigid gas permeable (RGP) contact lenses. The firmer material of a rigid contact lens holds the cornea in place better then a soft contact lens. Fitting contact lenses on a keratoconic cornea is delict and time consuming. You can expect frequent return visits to fine tune the fit and the prescription. The process will begin again when the cornea thins and distorts even more, altering the contact lens fit and prescription needed for clear, comfortable vision. Another treatment for keratoconus is corneal inserts. Intact corneal are to correct or reduce nearsightedness and astigmatism in kerataconus patients who can no longer obtain functional vision with contact lenses or eyeglasses. The procedure involves placing the plastic inserts just under the surface of the eye in the periphery of the cornea. The result is a flatter cornea and clearer vision.

Therefore, some patients are not comfortable with a RGP lenses alone in their eyes, so they need some kind of lenses that would give them comfort for their eyes. The one that is very comfortable and gives good vision correction is a piggyback lens combination, in which gas permeable rigid lenses are worn over soft lenses, which is both of them providing a degree of vision correction. The Wikipedia article says that fitting a piggyback lens combination requires experience on the part of the lens fitter, and tolerance on the part of the keratonic patient.

There are different types of contact lenses to correct kerataconus. There are Sope Cone lens, which is designed with a varying central posterior curve (CPC) that is chosen dependent on the radius of the patient’s cornea, and has a standard peripheral flange of 45.00D. There is also McGuire lens in manufactured with a series of blended curves resulting in a more aspheric posterior design. Another one is Nicone lens that has three posterior zones that become steeper as they near the center of the lens. Many people prefer Rose K lens because they are more comfortable fitting lens for patients and a better sight. Unlike traditional contact lenses, the complex geometry built into every Rouse K contact lens closely mimics the cone like shape of the cornea, for every stage of the condition. The Rose K lens has a number of features that make it ideal for keratoconus, for instance it’s complex geometry can be customized to suit each eye and can correct all on the myopia and astigmatism associated with kerakaconus. They are easy to insert, remove and clean. They provide excellent health to the eye, because they allow the cornea to breathe oxygen directly through the lens. Practitioners have the Rouse K lens trial set fitting system, which achieves a first fit success in over 80% of patients internationally.

A small number of cases of keratoconus keep getting worse, however, and, eventually, contact lenses cannot give clear vision. In other cases, the keratoconus or the use of contact lenses over the years will have side effects. These side effects can make the cornea cloudy. When these things happen, corneal transplantation might be recommended, also called a penetrating keratoplasty or corneal graft. A corneal transplant may be needed when the patient cannot see clearly with glasses and contact lenses or if a patient has pain, which cannot be revealed by medications. According to Angeles Vision Clinic, when the cornea becomes "opaque”, gray/white from injury, or painful from swelling, is no longer functions as the clear window of the eye. It then acts more like a soapy window, which you cannot clearly see through. Even if the rest of the eye is healthy, a cloudy cornea will obstruct clear vision. Even after a transplant, you most likely will need glasses or contact lenses for clear vision.

The process of surgery involves the removal of the central portion called a bottom of the diseased cornea and replacing it with clear healthy donor buttom. The donor cornea buttom is sewed into the defect created by removal of the diseased cornea. Tiny hair-thin sutures or stitches are used to anchor of the graft to the host tissue. The surgery is painless and usually done on an outpatient basis approximately the operation is going 60-90 minutes, followed by a short recovery time, in most cases patient will allow to go home soon afterward. (Angeles Vision Clinic 6)

The best way a patient can be help is through accurate fitting procedures. If followed correctly these procedures, it will help the clinician fit their patients to the best ability. In addition, it is supportive when the patient knows that he has a problem and then he would start to cure the keratoconus earlier. Vision is very important and helping someone see is something very great.

Bibliography

Angeles Vision Clinic. “What is Keratoconus and What are the Treatment Options?” March 9, 2006 http://www.avclinic.com/keratoconus.htm

Keratoconus Inserts. “What is Keratoconus” April 18, 2006 http://www.keratoconusinserts.com/what.htp

Wikipedia, the free encyclopedia. “Keratoconus.” April 18, 2006 http://en.wikipedia.org/wiki/Keratoconus