Vision correction procedure

With approximately 75% of Americans today suffering from some sort of visual impairment, the demand for new and innovative solutions or cures for visual problems is extremely high. Impaired vision has always been common, but the solutions have not always been effective until recently. For thousands of years, numerous scholars, scientists, inventors, and doctors have all tried to create solutions. Modern vision correction procedures are a result of the collaborative collection of information and observations made by those people. Now people have a wide variety of options, from non-surgical means, such as glasses or contacts, to surgical procedures like the popular LASIK procedure. Vision correction procedures have progressed considerably since ancient times and some of the most advanced and revolutionary technology of our time contributes to the correction of our vision.

Causes of impaired vision
Impaired vision is a prevalent health problem in today's society. Of the estimated 75% of American adults using some type of vision correction, about 64% of them wear eyeglasses and another 11% wear contact lenses. The eyesight may even vary between an individual's two eyes, a condition called anisometropia. Impaired vision can result from many causes; while poor eyesight is often a genetic attribute, people may get poor eyesight by overexposure to bright screens, eye diseases such as cataracts, or external injuries. When symptoms such as squinting or blurred vision become evident, patients seek a consultation with their optometrist, who tests for problems and offers a diagnosis and solution. Common causes of impaired vision include:
 * Myopia: Often called nearsightedness, myopia is a vision problem experienced by 30% of Americans. The person can see objects that are near clearly but distant objects become blurred. Myopia occurs when the cornea, lens, or both are too curved and the light from distant objects does not focus correctly on the back of the eye, producing blurred images. Myopia is usually diagnosed in people younger than 20 years old and is caused by a hereditary history of myopia or from a superfluous amount of "near-work", meaning extensive computer use or reading.
 * Presbyopia: Presbyopia is the normal loss of ability to focus on near objects for adults in their early 40's. It is caused by the thickening and loss of the flexibility of the crystalline lens of the eye. The process of accommodation in the eye thus has limited power and the eye cannot focus on objects that are within a close distance.
 * Hyperopia: Commonly referred to as farsightedness, hyperopia refers to the limited ability to focus on near objects. It is not to be confused with presbyopia, because hyperopia occurs during the younger ages and is not a natural effect of aging as it is in presbyopia.
 * Astigmatism: An astigmatism occurs when the cornea or lens (or both) are not perfectly symmetrical. Eyes that have an astigmatism are generally shaped more like a football rather than having an equal shape across the surface. This irregular shape prevents light from properly focusing to the retina and thus blurs vision.EDA14 72.jpg]]
 * Diabetic Retinopathy: Diabetic retinopathy can be experienced by anyone suffering from Type 1 or Type 2 diabetes. This occurs when the blood vessels of the light-sensitive tissue in the retina are damaged, leading to mild vision problems at first and possibly resulting in blindness. This may happen as a result of uncontrolled or poorly controlled blood sugar levels.
 * Cataract: A cataract is the clouding of the lens in a process that develops slowly. This condition is common among older people. By age 80, more than 50% of people in the U.S. have had a cataract or a cataract surgery.

History
Many have been trying to cure poor eyesight for thousands of years. Through the development of eyeglasses, contacts, and many laser surgeries, a variety of solutions are now available to the average person.

Eyeglass development
Vision correction procedures began developing in the ancient empires of Egypt and Rome. These ancients observed that when glass bowls were filled with water and held over books, the text became easier to read. This idea carried onto the 13th century where magnifying glasses were commonly used for reading. Historians believe Italy produced the first form of eyeglasses around 1285-1289. The eyeglasses were designed for reading and consisted of magnifying lenses set into bone, metal, or leather mountings with a frame that allowed them to be balanced on the bridge of the nose. Lenses were later developed in the 1400's to help with nearsightedness. In 1775, Benjamin Franklin developed the first bifocals, which accommodated both the nearsighted and farsighted. Monocles became popular in the 1800's. In 1825, Sir George Airy created eyeglasses designed to correct the problems of those suffering from an astigmatism. Since then, eyeglasses have become increasingly thinner, more effective, and more stylish.

Contact lens development
Eyeglasses would soon be followed by yet another advancement in vision correction procedures, contact lenses. Historians credit Leonardo da Vinci as the first to dream up the idea of contact lenses. He sketched and designed them in 1508, but actual contact lenses were not created for another 300 years. In 1887, German glassblower F.A. Muller fashioned the first glass contact lens. Shortly after that, A.E. Fick and Edouard Kalt fitted the first glass contact lenses to correct both nearsightedness and farsightedness. At this point, the lenses were large and could only be tolerated for a few hours. In 1948, Kevin Tuohy introduced the first all-plastic contact lenses. For the next twenty years, plastic lenses were made smaller, thinner, and more fitting to the shape of the eye. Due to the discomfort of the plastic lenses, scientists still sought to improve the design of contact lenses. Chemist Otto Wichterle's experimentation with producing contact lenses using a soft, water-absorbing plastic led to the release of the first soft contact lenses by Bausch & Lomb in 1971. This version of the contact lens is the one used most commonly today.

Eye surgery development
As contact lenses and eyeglasses were being developed, some scientists and doctors made efforts to correct vision through surgeries. The goal of the surgeries was to reshape the cornea and lens of the eye to improve the focus and the overall vision of the patient. The observations of Dr. Tsutomu Sato in 1936 and by Dr. Fyodorov in the 1960's were instrumental in helping American scientists develop the concept of vision correction surgeries. Fyodorov published a book in which he recounted his experience with a young boy whose vision had improved after an accident. The boy had fallen and his glasses shattered into his eye, shaving off a layer of the outer surface. The boy, who had previously been extremely nearsighted, had improved vision after the accident. Fyodorov published his findings and discussed a procedure in which part of the eye could be shaved off to improve vision. These findings inspired the creation of Radial Keratotomy, a surgery in which several small incisions were made on the surface of the cornea that radiated outward like the spokes on a bicycle wheel. This surgery was followed by Automated Lamellar Keratoplasty (ALK), a procedure in which the surgeon would create a thin flap. The results of these surgeries were often unpredictable and caused many adverse side effects, which led to the development of more stable surgeries.

American doctors took this knowledge and added a new component, the laser. In 1978, American doctors realized the potential of the Excimer laser (an ultraviolet laser) on biological tissue. Dr. Steven Trokel, an opthalmologist, who was the first to use the laser on the cornea, proceeded to use the same principles as that of radial keratotomy and ALK. Photorefractive keratectomy (PRK) was the first kind of corrective eye surgery to involve a laser. PRK was followed with the invention of Laser assisted in-situ keratomileusis (LASIK). This surgery, first conceived in 1989 by the Greek doctor Ioannis Pallikaris, became vastly more popular than the other surgeries. The FDA approved various types of laser surgery between 1995 and 2000. Around 1992, those at the Fyodoroc Institute in Russia developed Phakic Intraocular Lenses including Visian ICL, which involved the assertion of a lens into the eye. Since 2000, the FDA has approved new types of LASIK surgery including Wavefront, Intralase and LASIK. The success rate for these procedures is between 90 and 100 percent.

Nonsurgical solutions
Optometrists test the eyes of the patient. If impaired vision is detected, an optician will offer various non-surgical and surgical options for their vision correction. These non-surgical solutions are generally less expensive and more natural than the surgical solutions.

Corrective lens
Corrective lenses are designed to correct vision by properly focusing light to the back of the retina. There are a wide variety of corrective lenses, including several different types of eyeglasses and several different types of contact lenses.

Eyeglasses
Most people diagnosed with impaired vision first use eyeglasses to help improve vision. The convex shape of the glass focuses the light to the retina, thus improving overall vision. Since their invention, several innovations have been made to make eyeglasses more efficient and stylish. Not only are they being used to correct one's vision, but they are also becoming popular fashion accessories and can be purchased in stores without functional lenses. Glasses now have durable metal or plastic frames and thinner, lighter lenses despite high prescriptions. Aspheric lenses, which are not perfectly rounded on the surface, have recently been designed to correct for small distortions in vision that can be associated with more traditional lenses. Glasses are now made of polycarbonate or other high-index materials which are both lighter and stronger. Glasses now even come with lens coatings that can reduce glare, condensation, block UV rays, and resist scratching. Photochromic lenses are special lenses that have chemical coatings or special internal changes which allow the lenses to darken or lighten according to the brightness of the surroundings.

For those who have presbyopia, a number of eyeglass options are available. Many buy reading glasses that offer a near range of vision and which cost very little. Bifocals have both a near and far range vision in separate parts of the lens. Trifocals, which are a bit more uncommon, have three ranges of vision (near, far, and intermediate). Progressive lenses are more recently developed and function as bifocals or trifocals without the visible lines of separation on the lens.

Contact lens
Contact lenses are small plastic disks that are placed on the surface of the eye to improve the shape and thus direct light to the retina more accurately. Contact lenses provide a natural appearance as well as a full range of unobstructed vision useful for sports and other rigorous activities. The three types of contacts, classified by materials are:
 * Hard: Hard lenses are made from Plexiglas and are virtually obsolete.
 * RGP: Also called Rigid Gas Permeable lenses, RGP lenses are slightly smaller than the iris and are made from rigid, waterless plastics. These lenses are particularly good for presbyopia and high astigmatism. In children and adolescents, RGP lenses have been shown to decrease the fast progression of myopia. These can be used repeatedly over a period of at least a year.
 * Soft: Soft lenses are slightly larger than the iris and are made from gel-like, water-containing plastics. These are the kind that are most common because of their high level of comfort. There are several different types of soft lenses.
 * Disposable lenses have different disposal intervals, ranging from one day to every two months.
 * Daily wear contacts are used once a day while extended wear contacts can be worn overnight for up to 30 days.
 * Contact lens designs can range from those that are bifocals, those that can reshape the eyes at night for better vision in the morning, those that can correct astigmatism, etc.
 * Colored contacts are another type of soft lens that change the color of the iris.

Natural methods
Some people choose to try to permanently improve their vision through natural, non-surgical means. Promises of naturally restored vision have been rampant for years. Natural vision correction is a popular idea in which many people try to use specific exercises and diets to correct their own vision. Several websites and companies offer a regimen of exercises, diets, and treatments that are guaranteed to improve vision. The practitioners of this type of vision correction follow the Bates Method, created by an ophthalmologist William H. Bates in 1919. He believed that the causes of myopia, hyperopia, and other refractive errors were based on tension. Natural vision correction practitioners have convincing testimonials from patients and make promising claims, but their practice is not recognized in the field of medicine and does not have a proven track record of success.

Another way that people try to correct their vision naturally is through a diet that is high in specific vitamins. Nutrition can play a huge role in eye health. Researchers have discovered that foods high in Vitamins C and E, zinc, lutein, zeaxanthin, and omega-3 fatty acids DHA and EPA may be especially beneficial to the health of the eyes. To attain these vitamins, one should eat dark green leafy vegetables, citrus fruits, vegetable oils, nuts, whole-grains, and cold-water fish. In more serious cases, those who suffer from age-related macular degeneration (AMD) are advised to take Vitamin C, Vitamin E, Beta-carotene, Zinc Oxide, and Copper Oxide to slow the effects of macular degeneration.

CK
CK, which stands for Conductive Keratoplasty, is a non-surgical procedure used mainly on those suffering from hyperopia or presbyopia. In this procedure, low energy radio frequency light increases the curvature of the cornea. This procedure is relatively safe and effective, but the results are not very permanent.

Surgical procedures
Various surgical procedures have been created to correct vision. The procedures vary according to the individual's prescription or condition, but most are now conducted with the use of lasers. Candidates for surgery must be at least 18 years old, have had no changes in prescription for a year, and must not have certain eye or medical conditions. Candidates who seek surgery must find an experienced surgeon and set aside thousands of dollars for treatment. Different surgeries are more appropriate for different conditions, like myopia or hyperopia, and each one presents different risks. Though there is a wide range of eye surgeries, the following shows several of the most common surgical solutions to the most widely spread vision problems.

Replacement lens
Replacement lenses, such as the popular brand Crystalens, are an alternative for farsighted patients and cataract patients alike. In this surgery, the natural lens of the eye is removed through the use of a laser or and replaced with a plastic lens that is designed to work with the eye muscles and change focus naturally. An added benefit of this procedure is that it eliminates the risk of developing cataracts.

PRK/ASA
Photorefractive keratectomy (PRK) can be used on patients who have myopia, hyperopia, or an astigmatism. A laser removes parts of the cornea and reshapes the eye. There is no creation of a corneal flap. PRK presents more risks than LASIK, because it takes longer to heal, see results, and has an increased risk of scarring.

Advanced Surface Ablation (ASA) is the newer version of PRK. It eliminates the need for creating a corneal flap. Instead, the cells of the outer cornea are loosened and removed while a laser reshapes the cornea's surface. Afterwards, a contact lens must be worn to protect the eye during the healing process. Patients benefit from ASA because there is no actual cutting necessary to create a corneal flap and thus surgical flap complications are fewer. Though LASIK has become more popular than PRK since its invention, PRK is making a comeback due to studies that indicate that nerve regeneration occurs faster with PRK than with LASIK.

Implantable lens
Implantable lenses, such as Visian ICL and Verisyse, are lenses that are surgically inserted into the eye and work with the natural lens. Unlike other surgeries, these lenses do not alter the structure of the eye and instead work with the eye to enhance performance. This surgery involves a small incision, the insertion of an implantable lens, and an almost immediate improvement in visual acuity. Because the lenses are removable if necessary, the surgery is reversible unlike LASIK. This type of surgery can be more expensive than LASIK and may take a longer time to recover. Implantable lenses are particularly beneficial to patients whose prescriptions are too high for LASIK and for patients who have cataracts.

LASIK

 * Main Article: LASIK eye surgery‎

LASIK is the most popular refractive surgery. It shows results within hours and is relatively safe. LASIK resembles PRK, but includes the cutting of a thin, hinged flap made on the surface of the eye. The flap is lifted and a laser works to reshape the eye. Once the laser reshapes the eye, the flap is replaced and acts as a type of natural bandage to promote quick healing. Other than the traditional procedure, there are two additional types of LASIK. Bladeless LASIK is the same as LASIK, but cuts the flap with a laser instead of with a knife. Wavefront LASIK uses a system called Wavefront Analysis to measure exactly how light travels through the eye. Lasers with Wavefront built in can detect and compensate for vision errors as it reshapes the cornea.

Monovision
Some people opt for monovision during their LASIK procedure. In this procedure, one eye is corrected for near vision and one is corrected for far vision. This process can potentially allow a person to have much improved vision, but may be difficult to adjust to.

LASEK
Laser Epithelial Keratomileusis (LASEK) resembles LASIK, but does not involve a flap being cut. Alcohol is used to float the epithelium which gives the surgeon enough room to correct the cornea. This option is particularly good for patients who have certain have large pupils or dry eyes.

EpiLASIK
EpiLASIK resembles LASIK and LASEK, but does not involve cutting the cornea or the use of alcohol. In this surgery, a mechanical device makes the separation needed, which avoids the cell damage caused by alcohol. This surgery is ideal for people with thin corneas.

Keratoplasty
Keratoplasties, commonly known as corneal transplants, are some of the most extreme procedures to correct vision. A corneal transplant involves replacing part of the patient's cornea with the cornea of a deceased donor. This can restore vision, reduce pain, and even improve the appearance of the eye. Keratoplasties are the most common transplant operations in the United States, with about 40,000 being performed each year.

Focal/Scatter laser treatment
These treatments are extremely similar and are both used to help those suffering from diabetic retinopathy. Also known as photocoagulation, focal laser treatment is an outpatient procedure in which laser burns are used to stop or slow the leakage of blood and fluid in the eye. This surgery is performed in one session and can show results as early as after one day. Scatter laser treatment, also known as panretinal photocoagulation, involves treating the areas of the retina away from the macula with scattered laser burns, which cause the abnormal blood vessels to shrink and scar. This procedure is usually done in two or more sessions, but also has results after one day.