Tag Archives: Myopia

Astigmatism

Definition:
Astigmatism is a common, mild and generally easily treatable imperfection in the curvature of your eye. The condition can cause blurred vision.

Astigmatism occurs when the front part of the eye, the cornea, is not a regular symmetrical spherical shape. Instead, its shape is rather like that of the back of a spoon – longer in one direction than another. Because the cornea is an irregular shape, the eye can’t focus light passing through it sharply on to the back of the eye or retina. So vision is blurred at all distances.
CLICK & SEE THE PICTURES

Astigmatism is often present at birth and may occur in combination with nearsightedness or farsightedness. Often it’s not pronounced enough to require corrective action. When it is, your treatment options include corrective lenses and surgery.

Many people have some degree of astigmatism. In fact, it is rare to find a perfectly formed eye. Astigmatism appears to run in families and is often present from birth. If you have astigmatism, chances are good your children will have it also. It may worsen slowly over time but may remain fairly stable throughout life. Astigmatism often occurs with other vision conditions such as nearsightedness (myopia) and farsightedness (hyperopia.)

Symptoms:
Signs and symptoms of astigmatism may include:

*Blurred or distorted vision
*Headaches
*Eye strain
*Fatigue
*Blurred vision at certain distances

The most common symptom of astigmatism is blurred vision. Some people describe it as double vision but in only one eye. As a result of trying to focus on near or distant objects, a patient may develop eyestrain, squinting and headaches. Note the diagram at right – a person WITHOUT astigmatism would see all the radial lines as perfectly sharp and with the same contrast. The diagram  below illustrates how some lines might appear clearer than others to a person with astigmatism.

Children with astigmatism may be too young to notice or describe astigmatism. They may frown, squint, or pull objects close in an effort to get a clearer picture. They may also tilt or turn their head. This extra effort can lead to eyestrain, fatigue or reduced reading efficiency.

Causes:
As the eye develops in the womb, several factors determine the shape of it, including inherited genetic factors and environment. It would seem that these factors can lead to an irregular curvature of the cornea, although the exact cause isn’t known.

Your eye has two parts that focus images — the cornea and the lens. In a perfectly shaped eye, each of these focusing elements has a perfectly smooth curvature, like the surface of a smooth ball. A cornea or lens with such a surface curvature bends (refracts) all incoming light the same way and makes a sharply focused image on the back of your eye (retina).

However, if your cornea or lens isn’t evenly and smoothly curved, the light rays aren’t refracted properly. This causes a refractive error. Astigmatism is one type of refractive error. In astigmatism, your cornea or lens is curved more steeply in one direction than in another. When the cornea has a distorted shape, you have corneal astigmatism. When the lens is distorted, you have lenticular astigmatism. Either type of astigmatism can cause blurred vision. Blurred vision may occur more in one direction — either horizontally, vertically or diagonally.

Astigmatism may occur in combination with other refractive errors, which include:

*Nearsightedness (myopia).
This occurs when your cornea is curved too much or your eye is longer than normal. Instead of being focused precisely on your retina, light is focused in front of your retina, resulting in a blurry appearance for distant objects.
*Farsightedness (hyperopia). This occurs when your cornea is curved too little or your eye is shorter than normal. The effect is the opposite of nearsightedness. When your eye is in a relaxed state, light is focused behind the back of your eye, making nearby objects blurry.

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Astigmatism may be present from birth, or it may develop after an eye injury, disease or surgery. Astigmatism isn’t caused or made worse by reading in poor light, sitting too close to the television or squinting.

Test & Diagnosis :

The Simple Astigmatism test :
1.If you have contacts or glasses, wear them.
2.Sit about 14 inches away from your computer screen.
3.Cover one eye.
4.Note how the lines and squares appear (for example, wavy or blurred).
5.Test the other eye in the same manner.

To a normal eye, the lines will appear sharply focused and equally dark. If some sets of lines appear sharply focused and dark while others are blurred and less dark, you may have astigmatism. Regardless of your result, see your eye doctor on a regular basis for a complete eye exam.

To diagnose astigmatism, your eye doctor may:

*Measure reflected light. By measuring light reflected from the surface of your cornea, a device known as a keratometer quantifies the amount and orientation of corneal astigmatism.
*Measure the curvature of your cornea. Using light to project rings on to your cornea, a device called a keratoscope measures the amount of curvature to your cornea’s surface and can confirm the presence of astigmatism. Observation through the keratoscope of the reflection of light from your cornea and inspection of the shape and spacing of the rings provide information about the degree of astigmatism.

To measure the change in corneal surface curvature, a process called corneal topography is used. Corneal topography uses a videokeratoscope, which is a keratoscope fitted with a video camera.

Treatment:
The goal of treating astigmatism is to address the uneven curvature that’s causing your blurred vision. Treatments include wearing corrective lenses and undergoing refractive surgery.

Corrective lenses
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Wearing corrective lenses treats astigmatism by counteracting the uneven curvature of your cornea. Types of corrective lenses are:

*Eyeglasses. Eyeglasses can be made with special lenses that help compensate for the uneven shape of your eye. In addition to correcting astigmatism, eyeglasses can also correct for other refractive errors, such as nearsightedness or farsightedness.

*Contact lenses
. Like eyeglasses, contact lenses can correct astigmatism. A wide variety of contact lenses are available — hard, soft, extended wear, disposable, rigid gas permeable and bifocal. Ask your eye doctor about the pros and cons of each and which contact lenses might be best for you.

Contact lenses are also used in a procedure called orthokeratology, or Ortho-K. In orthokeratology, you wear rigid contact lenses for several hours a day until the curvature of your eye improves. Then, you wear the lenses less frequently to maintain the new shape. If you discontinue this treatment, your eyes return to their former shape. Wearing contact lenses for extended periods of time increases the risk of infection in the eye.

Refractive surgery;
This astigmatism treatment method corrects the problem by reshaping the surface of your eye. Refractive surgery methods include:

*LASIK surgery.
Laser-assisted in-situ keratomileusis (LASIK) is a procedure in which a doctor uses an instrument called a keratome to make a thin, circular hinged cut into your cornea. Alternatively, this same cut can be made with a special cutting laser. The surgeon lifts the flap and then uses an excimer laser to sculpt the shape of the cornea under the flap. An excimer laser differs from other lasers in that it doesn’t produce heat.

*Photorefractive keratectomy (PRK).
In PRK, your surgeon removes the outer protective layer of the cornea before using an excimer laser to change the curvature of the cornea.

*Laser-assisted subepithelial keratomileusis (LASEK).
In this procedure, a much thinner layer of cornea is folded back, which makes your eye less vulnerable to damage should an injury occur. LASEK may be a better option if you have a thin cornea or if you’re at high risk of an eye injury at work or from playing sports.

Radial keratotomy is a procedure that was used in the past to correct astigmatism. However, it’s not commonly performed anymore.

Conclusion:
If you experience a distortion or blurring of images at all distances — nearby as well as far — you may have astigmatism. Even if your vision is fairly sharp, headache, fatigue, squinting and eye discomfort or irritation may indicate a slight degree of astigmatism. A thorough eye examination, including tests of near vision, distant vision and vision clarity, can determine if astigmatism is present. Your eye doctor can answer any questions you may have about the various methods for correcting astigmatism and other vision problems.

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose.
Resources:
http://www.bbc.co.uk/health/physical_health/conditions/astigmatism2.shtml
http://www.dcareaeyecare.com/astigmatism_article.html
http://www.mayoclinic.com/health/astigmatism/DS00230
http://www.lasersurgeryforeyes.com/astigmatism.html#Symptoms
http://www.webmd.com/eye-health/understanding-astigmatism-basics
http://www.jnjvision.com/thinking-whocanwear-test.htm

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Presbyopia

Definition:
Presbyopia (Greek word “presbys”, meaning “old person”) describes the condition where the eye exhibits a progressively diminished ability to focus on near objects with age. Presbyopia’s exact mechanisms are not known with certainty, however, the research evidence most strongly supports a loss of elasticity of the crystalline lens, although changes in the lens’s curvature from continual growth and loss of power of the ciliary muscles (the muscles that bend and straighten the lens) have also been postulated as its cause.

………CLICK & SEE THE PICTURES

Similar to grey hair and wrinkles, presbyopia is a symptom caused by the natural course of aging presbyopia is the gradual loss of your eyes’ ability to focus actively on nearby objects — is a not-so-subtle reminder that you’ve reached middle age. A natural, often annoying part of aging, presbyopia usually develops after age 40.The first symptoms (described below) are usually first noticed between the ages of 40-50. The ability to focus on near objects declines throughout life, from an accommodation of about 20 dioptres (ability to focus at 50 mm away) in a child to 10 dioptres at 25 (100 mm) and leveling off at 0.5 to 1 dioptre at age 60 (ability to focus down to 1-2 meters only).

Symptoms
The first symptoms most people notice are difficulty reading fine print, particularly in low light conditions, eyestrain when reading for long periods, blur at near or momentarily blurred vision when transitioning between viewing distances. Many advanced presbyopes complain that their arms have become “too short” to hold reading material at a comfortable distance.

Presbyopia, like other focus defects, becomes much less noticeable in bright sunlight. This is a result of the iris closing to a smaller diameter. As with any lens, increasing the focal ratio of the lens increases depth of field by reducing the level of blur of out-of-focus objects (compare the effect of aperture on depth of field in photography).

A delayed onset of seeking correction for presbyopia has been found among those with certain professions and those with miotic pupils. In particular, farmers and housewives seek correction later, whereas service workers and construction workers seek eyesight correction earlier.

Focusing mechanism of the eye:
In optics, the closest point at which an object can be brought into focus by the eye is called the eye’s near point. A standard near point distance of 25 cm is typically assumed in the design of optical instruments, and in characterizing optical devices such as magnifying glasses.

There is some confusion in articles and even textbooks over how the focusing mechanism of the eye actually works. In the classic book, ‘Eye and Brain’ by Gregory, for example, the lens is said to be suspended by a membrane, the ‘zonula’, which holds it under tension. The tension is released, by contraction of the ciliary muscle, to allow the lens to fatten, for close vision. This would seem to imply that the ciliary muscle, which is outside the zonula must be circumferential, contracting like a sphincter, to slacken the tension of the zonula pulling outwards on the lens. This is consistent with the fact that our eyes seem to be in the ‘relaxed’ state when focusing at infinity, and also explains why no amount of effort seems to enable a myopic person to see further away. Many texts, though, describe the ‘ciliary muscles’ (which seem more likely to be just elastic ligaments and not under any form of nervous control) as pulling the lens taut in order to focus at close range. This has the counterintuitive effect of steepening the lens centrally (increasing its power) and flattening peripherally.

Presbyopia and the ‘payoff’ for the nearsighted
Many people with myopia are able to read comfortably without eyeglasses or contact lenses even after age 40. However, their myopia does not disappear and the long-distance visual challenges will remain. Myopes with astigmatism will find near vision better though not perfect without glasses or contact lenses once presbyopia sets in, but the greater the amount of astigmatism the poorer their uncorrected near vision. Myopes considering refractive surgery are advised that surgically correcting their nearsightedness may actually be a disadvantage after the age of 40 when the eyes become presbyopic and lose their ability to accommodate or change focus because they will then need to use glasses for reading. A surgical technique offered is to create a “reading eye” and a “distance vision eye”, a technique commonly used in contact lens practice, known as monovision. Monovision can be created with contact lenses or spectacles so candidates for this procedure can determine if they are prepared to have their corneas reshaped by surgery to cause this effect permanently.

Causes:
Presbyopia is caused by an age-related process. This is different from astigmatism, nearsightedness and farsightedness, which are related to the shape of the eyeball and caused by genetic factors, disease or trauma. Presbyopia is generally believed to stem from a gradual loss of flexibility in the natural lens inside your eye.

These age-related changes occur within the proteins in the lens, making the lens harder and less elastic with the years. Age-related changes also take place in the muscle fibers surrounding the lens. With less elasticity, the eye has a harder time focusing up close. Other, less popular theories exist as well.

Most experts agree that presbyopia is caused by a hardening of your lens, which in turn develops with aging. As your lens becomes less flexible, it can no longer change shape, and close-up images appear out of focus.

Tests and diagnosis:
Presbyopia is diagnosed by a basic eye exam. This exam is generally administered by either an ophthalmologist or an optometrist. An ophthalmologist, who has a doctor of medicine (M.D.) degree, is a specialist trained to diagnose and manage eye disorders, including those that may require either medical or surgical treatment. An optometrist, who has a doctor of optometry (O.D.) degree, can perform many of the same services as an ophthalmologist, such as evaluating your vision, prescribing corrective lenses and diagnosing common eye disorders. In some states, optometrists also treat selected eye disorders with drugs. However, an optometrist may refer you to an ophthalmologist for more complex eye problems and for surgical procedures.

A complete eye examination involves a series of tests. Your eye doctor may use odd-looking instruments, aim bright lights directly at your eyes and request that you look through an array of lenses. Each test is necessary and allows your doctor to evaluate a different aspect of your vision.

According to the American Academy of Ophthalmology, if you don’t wear glasses or contacts, have no symptoms of eye trouble and are at a low risk of developing eye disease, you should have your eyes examined at the following intervals:

*Every five to 10 years under age 40
*Every two to four years between ages 40 and 64
*Every one to two years beginning at age 65

However, if you wear glasses or contacts, have your eyes checked more often. And if you notice any problems with your vision, schedule an appointment with your eye doctor as soon as possible, even if you’ve recently had an eye exam. Blurred vision may suggest you need a prescription change or have another eye problem that may need evaluation and treatment.

Treatment:
Presbyopia is not routinely curable – though tentative steps toward a possible cure suggest that this may be possible – but the loss of focusing ability can be compensated for by corrective lenses including eyeglasses or contact lenses. In subjects with other refractory problems, convex lenses are used. In some cases, the addition of bifocals to an existing lens prescription is sufficient. As the ability to change focus worsens, the prescription needs to be changed accordingly.

In order to reduce the need for bifocals or reading glasses, some people choose contact lenses to correct one eye for near and one eye for far with a method called “monovision”. Monovision sometimes interferes with depth perception. There are also newer bifocal or multifocal contact lenses that attempt to correct both near and far vision with the same lens.

Controversially, eye exercises have been quoted as a way to delay the onset of presbyopia, but there is no evidence that they work.

Nutrition
At least one scientific study reported that taking lutein supplements or otherwise increasing the amount of lutein in the diet resulted in an improvement in visual acuity, while another study suggested that lutein supplementation might slow aging of the lens. Lutein is found naturally in both the lens of the eye and the macula, the central area of the retina.

The goal of treatment is to compensate for the inability of your eyes to focus on nearby objects. Treatment options include wearing corrective lenses, undergoing refractive surgery or getting lens implants.

Corrective lenses
If you had good, uncorrected vision before developing presbyopia, you may be able to use nonprescription reading glasses. But check with your eye doctor about what’s right for you.

Reading glasses sold over-the-counter are labeled on a scale that corresponds to the degree of magnification (power). The least powerful are labeled +1.00, and the most powerful +3.00. When purchasing reading glasses, try out a few different powers until you find the magnification that allows you to read comfortably. Test each pair on printed material held about 14 to 16 inches in front of your face.

You’ll need prescription lenses for presbyopia if over-the-counter glasses are inadequate or if you already wear corrective lenses for nearsightedness, farsightedness or astigmatism. Your choices include:

Prescription reading glasses. If you have no other vision problems, you can have prescription lenses for reading only.

Bifocals. These glasses come in two styles — those with a visible horizontal line and those without a line (progressive bifocals). When you look through progressive bifocals at eye level, the lenses correct your distance vision. This correction gradually changes to reading correction at the bottom.

Trifocals. These glasses have corrections for close work, middle-distance vision — such as for computer screens — and distance vision. Trifocals can have visible lines or progressive lenses.

Bifocal contacts. Bifocal contact lenses, like bifocal glasses, provide distance and close-up correction on each contact. The bottom, reading portion of the lens is weighted to keep the lens correctly positioned on your eye. These are frequently difficult to fit and often do not provide altogether satisfactory visual results.

Monovision contacts. With monovision contacts, you wear a contact lens for distance vision in your dominant eye and a contact lens for close-up vision in your nondominant eye. Your dominant eye is generally the one you use when you’re aiming a camera to take a picture.

Modified monovision. With this option, you wear a bifocal contact lens in your nondominant eye and a contact lens set for distance in your dominant eye. You use both eyes for distance and one eye for reading. Your brain learns which lens to favor — depending on whether you’re viewing things close up or far away — so you don’t have to consciously make the choice of which eye to use.

Refractive surgery:-
Refractive surgery changes the shape of your cornea. For presbyopia, this treatment — equivalent to wearing monovision contact lenses — may be used to improve close-up vision in the nondominant eye. The American Academy of Ophthalmology recommends that people try monovision contacts to determine if they can adjust to this kind of correction before considering refractive surgery.

Most refractive surgical procedures were developed to correct nearsightedness, farsightedness and astigmatism. Few studies have been published about the long-term effectiveness of monovision refractive surgery for people with presbyopia, but some evidence suggests that the surgery may help some people with presbyopia reduce their dependence on corrective lenses. Eventually, though, many people who have had refractive surgery will still need corrective lenses for reading.

Refractive surgical procedures include the following:

Conductive keratoplasty (CK). This procedure uses radio frequency energy to apply heat to very tiny spots around the cornea. The degree of change in the cornea’s curvature depends on the number and spacing of the spots, as well as the way in which the corneal tissue heals after the treatment. The results of CK are variable and unstable in many people.

New surgical options to treat presbyopia are being researched and are already available in many countries. One example is Refractec Inc.’s conductive keratoplasty, or NearVision CK treatment, which uses radio waves to create more curvature in the cornea for a higher “plus” prescription to improve near vision. The method was FDA-approved for the temporary reduction of presbyopia in April 2004. (In 2002 it had been approved for mild farsightedness.) Click to read more about how CK works.
…………………….CLICK & SEE

The eye’s lens stiffens with age, so it is less able to focus when you view something up close. The result is blurred near vision. (Illustration: Varilux).
A highly experimental treatment is a soft, elastic polymer gel that researchers say would be injected into the capsular bag, the cavity that contains the natural lens. In theory, the gel would replace the natural lens and serve as a new, more elastic lens. Experiments also have centered on laser treatment of the eye’s hardened lens to increase flexibility and improve focus.

With the recent introduction of presbyopia-correcting intraocular lenses, some people undergoing cataract surgery may be able to achieve clear vision at all distances. Also, an elective procedure known as refractive lens exchange may enable you to replace your eye’s natural lens with an artificial one using presbyopia-correcting lenses.

Other methods are being researched as well. Click to read more about surgical options for presbyopia.

Laser-assisted in-situ keratomileusis (LASIK). With this procedure, your eye surgeon uses a laser or an instrument called a keratome to make a thin, hinged flap in your cornea. Your surgeon then uses an excimer laser to remove inner layers of your cornea to steepen its domed shape. An excimer laser differs from other lasers in that it doesn’t produce heat.

Laser epithelial keratomileusis (LASEK). Instead of creating a flap in the cornea, the surgeon creates a flap only in the cornea’s thin protective cover (epithelium). Your surgeon will use an excimer laser to reshape the cornea’s outer layers and steepen its curvature and then reposition the epithelial flap.

Photorefractive keratectomy (PRK). This procedure is similar to LASEK, except the surgeon removes the epithelium. It will grow back naturally, conforming to your cornea’s new shape.

Lens implants
Another procedure used by some ophthalmologists involves removal of your clear natural lens and replacement with a synthetic lens inside your eye (intraocular lens implant). The synthetic lens implant is designed to allow your eye to see things both near and at a distance. However, synthetic lens implants haven’t been entirely satisfactory; recipients have experienced problems with glare and blurring. In addition, this surgery carries with it the same risks associated with cataract surgery, such as inflammation, infection, bleeding and glaucoma.

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Lifestyle modification and home remedies:
Although you can’t prevent presbyopia, you can help protect your eyes and your vision. Follow these steps:

Have your eyes checked. Regardless of how well you see, have your eyes checked regularly for problems.
Control chronic health conditions. Certain conditions, such as diabetes and high blood pressure, can affect your vision if you don’t receive proper treatment.

Recognize symptoms. Sudden loss of vision in one eye, sudden hazy or blurred vision, flashes of light, black spots, or halos or rainbows around lights may signal a serious medical problem, such as acute glaucoma or stroke, or some other treatable retinal condition, such as a retinal tear or retinal detachment. Talk to your doctor if you experience any of these symptoms.

Protect your eyes from the sun. Wear sunglasses that block ultraviolet (UV) radiation. This is especially important if you spend long hours in the sun or are taking a prescription medication that increases your sensitivity to UV radiation.

Eat healthy foods. Try to eat plenty of fruits and leafy greens and other vegetables; these foods generally contain high levels of antioxidants as well as vitamin A and beta carotene. They’re also vital to maintaining healthy vision.
Use the right glasses. The right glasses optimize your vision. Having regular exams will ensure that your eyeglass prescription is correct.
Use good lighting. Turn up the light for better vision.

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose.
Resources:
http://en.wikipedia.org/wiki/Presbyopia
http://www.allaboutvision.com/conditions/presbyopia.htm
MayoClinic.com

LASIK Eye Surgery

Introduction:LASIK or Lasik (laser-assisted in situ keratomileusis) is a type of refractive laser eye surgery performed by ophthalmologists for correcting myopia, hyperopia, and astigmatism. The procedure is generally preferred to photorefractive keratectomy, PRK, (also called ASA, Advanced Surface Ablation) because it requires less time for the patient’s recovery, and the patient feels less pain overall.

It is a  surgical procedure intended to reduce a person’s dependency on glasses or contact lenses. LASIK  is a procedure that permanently changes the shape of the cornea, the clear covering of the front of the eye, using an excimer laser. However, there are instances where a PRK/ASA procedure is medically justified as being a better alternative to LASIK.

.Click to see:LASIK Eye Surgery pictures

The LASIK technique was made possible by the Colombia-based Spanish ophthalmologist Jose Barraquer, who, around 1950 in his clinic in Bogotá, Colombia, developed the first microkeratome, used to cut thin flaps in the cornea and alter its shape, in a procedure called keratomileusis. Stephan Schaller assisted in this landmark procedure. Barraquer also researched the question of how much of the cornea had to be left unaltered to provide stable long-term results.

The eye and vision errors
The cornea is a part of the eye that helps focus light to create an image on the retina. It works in much the same way that the lens of a camera focuses light to create an image on film. The bending and focusing of light is also known as refraction. Usually the shape of the cornea and the eye are not perfect and the image on the retina is out-of-focus (blurred) or distorted. These imperfections in the focusing power of the eye are called refractive errors.

There are three primary types of refractive errors:

*Myopia: persons with myopia, or nearsightedness, have more difficulty seeing distant objects as clearly as near objects.

*Hyperopia: persons with hyperopia, or farsightedness, have more difficulty seeing near objects as clearly as distant objects.

*Astigmatism: astigmatism is a distortion of the image on the retina caused by irregularities in the cornea or lens of the eye.

Combinations of myopia and astigmatism or hyperopia and astigmatism are common. Glasses or contact lenses are designed to compensate for the eye’s imperfections. Surgical procedures aimed at improving the focusing power of the eye are called refractive surgery. In LASIK surgery, precise and controlled removal of corneal tissue by a special laser reshapes the cornea changing its focusing power.

Other types of refractive surgery:-
Radial Keratotomy or RK and Photorefractive Keratectomy or PRK are other refractive surgeries used to reshape the cornea. In RK, a very sharp knife is used to cut slits in the cornea changing its shape. PRK was the first surgical procedure developed to reshape the cornea, by sculpting, using a laser. Later, LASIK was developed. The same type of laser is used for LASIK and PRK. Often the exact same laser is used for the two types of surgery. The major difference between the two surgeries is the way that the stroma, the middle layer of the cornea, is exposed before it is vaporized with the laser. In PRK, the top layer of the cornea, called the epithelium, is scraped away to expose the stromal layer underneath. In LASIK, a flap is cut in the stromal layer and the flap is folded back.

Another type of refractive surgery is thermokeratoplasty in which heat is used to reshape the cornea. The source of the heat can be a laser, but it is a different kind of laser than is used for LASIK and PRK. Other refractive devices include corneal ring segments that are inserted into the stroma and special contact lenses that temporarily reshape the cornea (orthokeratology).

FDA regulations:-
In the United States, the Food and Drug Administration (FDA) regulates the sale of medical devices such as the lasers used for LASIK. Before a medical device can be legally sold in the U.S., the person or company that wants to sell the device must seek approval from the FDA. To gain approval, they must present evidence that the device is reasonably safe and effective for a particular use, the “indication.” Once the FDA has approved a medical device, a doctor may decide to use that device for other indications if the doctor feels it is in the best interest of a patient. The use of an approved device for other than its FDA-approved indication is called “off-label use.” The FDA does not regulate the practice of medicine.

The FDA does not have the authority to:
*Regulate a doctor’s practice. In other words, FDA does not tell doctors what to do when running their business or what they can or cannot tell their patients.

*Set the amount a doctor can charge for LASIK eye surgery. “Insist” the patient information booklet from the laser manufacturer be provided to the potential patient.

*Make recommendations for individual doctors, clinics, or eye centers. FDA does not maintain nor have access to any such list of doctors performing LASIK eye surgery.

*Conduct or provide a rating system on any medical device it regulates.

The first refractive laser systems approved by FDA were excimer lasers for use in PRK to treat myopia and later to treat astigmatism. However, doctors began using these lasers for LASIK (not just PRK), and to treat other refractive errors (not just myopia). Over the last several years, LASIK has become the main surgery doctors use to treat myopia in the United States. More recently, some laser manufacturers have gained FDA approval for laser systems for LASIK to treat myopia, hyperopia and astigmatism and for PRK to treat hyperopia and astigmatism.
When LASIK is  not for YOU ?

You are probably NOT a good candidate for refractive surgery if:

*You are not a risk taker. Certain complications are unavoidable in a percentage of patients, and there are no long-term data available for current procedures.

*It will jeopardize your career. Some jobs prohibit certain refractive procedures. Be sure to check with your employer/professional society/military service before undergoing any procedure.

*Cost is an issue. Most medical insurance will not pay for refractive surgery. Although the cost is coming down, it is still significant.

*You required a change in your contact lens or glasses prescription in the past year
. This is called refractive instability. Patients who are more likely to have refractive instability and probably should not have a refractive procedure are:

*In their early 20s or younger,
*Whose hormones are fluctuating due to disease such as diabetes,
*Who are pregnant or breastfeeding, or
*Who are taking medications such as steroids that cause fluctuations in vision.

*You have a disease or are on medications that may affect wound healing. Certain conditions, such as autoimmune diseases (e.g., lupus, rheumatoid arthritis), immunodeficiency states (e.g., HIV) and diabetes, and some medications (e.g., retinoic acid and steroids) may prevent proper healing after a refractive procedure.

*You actively participate in contact sports. You participate in boxing, wrestling, martial arts or other activities in which blows to the face and eyes are a normal occurrence.

*You are not an adult.
Currently, no lasers are approved for LASIK on persons under the age of 18.

Contraindications.
The safety and effectiveness of refractive procedures has not been determined in patients with some diseases. Do NOT have LASIK surgery if you have a history of any of the following:

*Herpes simplex or Herpes zoster (shingles) involving the eye area.
*Glaucoma, glaucoma suspect, or ocular hypertension.
*Eye diseases, such as uveitis/iritis (inflammations of the eye) and blepharitis (inflammation of the eyelids with crusting of the eyelashes).
*Eye injuries or previous eye surgeries.
*Keratoconus

Other Risk Factors:-some of the more frequently reported complications of LASIK:
*Surgery induced dry eyes
*Overcorrection[ or undercorrection
*Visual acuity fluctuation
*Halos or starbursts around light sources at night
*Light sensitivity
*Ghost images or double vision
*Wrinkles in flap (striae)
*Decentered ablation
*Debris or growth under flap
*Thin or buttonhole flap
*Induced astigmatism
*Corneal Ectasia
*Floaters
*Epithelium erosion
*Posterior vitreous detachment
*Macular hole

Complications due to LASIK have been classified as those that occur due to preoperative, intraoperative, early postoperative, or late postoperative sources

 

A subconjunctival hemorrhage is a common and minor post-LASIK complication.

Your doctor should screen you for the following conditions or indicators of risk:

*Large pupils. Make sure this evaluation is done in a dark room. Younger patients and patients on certain medications may be prone to having large pupils under dim lighting conditions. This can cause symptoms such as glare, halos, starbursts, and ghost images (double vision) after surgery. In some patients these symptoms may be debilitating. For example, a patient may no longer be able to drive a car at night or in certain weather conditions, such as fog.

*Thin Corneas. The cornea is the thin clear covering of the eye that is over the iris, the colored part of the eye. Most refractive procedures change the eye’s focusing power by reshaping the cornea (for example, by removing tissue). Performing a refractive procedure on a cornea that is too thin or has too few cells lining the back surface (endothelial cells) may result in blinding complications.

*Previous refractive surgery (e.g., RK, PRK, LASIK). Additional refractive surgery may not be recommended. The decision to have additional refractive surgery must be made in consultation with your doctor after careful consideration of your unique situation.

*Dry Eyes.
LASIK surgery tends to aggravate this condition.

Risk Factors:
Most patients are very pleased with the results of their refractive surgery. However, like any other medical procedure, there are risks involved. That’s why it is important for you to understand the limitations and possible complications of refractive surgery.

Before undergoing a refractive procedure, you should carefully weigh the risks and benefits based on your own personal value system, and try to avoid being influenced by friends that have had the procedure or doctors encouraging you to do so.

*You may be undertreated or overtreated. Only a certain percent of patients achieve 20/20 vision without glasses or contacts. You may require additional treatment, but additional treatment may not be possible. You may still need glasses or contact lenses after surgery. This may be true even if you only required a very weak prescription before surgery. If you used reading glasses before surgery, you will still need reading glasses after surgery.
*Results are generally not as good in patients with very small amounts of astigmatism or very large refractive errors of any type. You should discuss your expectations with your doctor and realize that you may still require glasses or contacts after the surgery.
*Results may not be lasting. The level of improved vision you experience after surgery may be temporary, especially if you are farsighted or currently need reading glasses. It is especially important for farsighted individuals to have a cycloplegic refraction (a vision exam with lenses after dilating drops) as part of the screening process. Patients whose manifest refraction (a vision exam with lenses before dilating drops) is very different from their cycloplegic refraction are more likely to have temporary results.
*Some patients lose vision. Some patients lose lines of vision on the vision chart that cannot be corrected with glasses, contact lenses, or surgery as a result of treatment. There is little known about how refractive procedures affect other aspects of vision, such as contrast sensitivity (the ability to see objects clearly against a similar background or in dim lighting conditions). Some studies suggest that patients do not see as well in situations of low contrast, such as at night or in fog, after treatment as compared to before treatment. Therefore, patients with low contrast sensitivity to begin with probably should not have a refractive procedure. It is important for you to know that not all eye centers test contrast sensitivity, and that when it is tested, it should be done in a dark room.
*Some patients may develop severe dry eye syndrome. As a result of surgery, your eye may not be able to produce enough tears to keep the eye moist and comfortable. This condition may be permanent. Intensive drop therapy and the use of plugs or other procedures may be required.
Additional Risks if you are Considering the Following:

Monovision
Monovision is one clinical technique used to deal with the correction of presbyopia, the gradual loss of the ability of the eye to change focus for close-up tasks that progresses with age. The intent of monovision is for the presbyopic patient to use one eye for distance viewing and one eye for near viewing. This practice was first applied to fit contact lens wearers and more recently to LASIK and other refractive surgeries. With contact lenses, a presbyopic patient has one eye fit with a contact lens to correct distance vision, and the other eye fit with a contact lens to correct near vision. In the same way, with LASIK, a presbyopic patient has one eye operated on to correct the distance vision, and the other operated on to correct the near vision. In other words, the goal of the surgery is for one eye to have vision worse than 20/20, the commonly referred to goal for LASIK surgical correction of distance vision. Since one eye is corrected for distance viewing and the other eye is corrected for near viewing, the two eyes no longer work together. This results in poorer quality vision and a decrease in depth perception. These effects of monovision are most noticeable in low lighting conditions and when performing tasks requiring very sharp vision. Therefore, you may need to wear glasses or contact lenses to fully correct both eyes for distance or near when performing visually demanding tasks, such as driving at night, operating dangerous equipment, or performing occupational tasks requiring very sharp close vision (e.g., reading small print for long periods of time).

Many patients cannot get used to having one eye blurred at all times. The difference between monovision with contact lenses and monovision with LASIK is that you can always take contact lenses out or have them changed (the treatment is reversible and adjustable) as opposed to LASIK, where the result of the surgery is not reversible or adjustable. Therefore, if you are considering monovision with LASIK, make sure you go through a trial period with contact lenses to see if you can tolerate monovision, before having the irreversible surgery performed on your eyes. Just before this trial period starts, find out if you pass your state’s driver’s license requirements with monovision, or if you need supplemental glasses to drive.

In addition, you should consider how much your presbyopia is expected to increase in the future. Ask your doctor when you should expect the results of your monovision surgery to no longer be enough for you to see near-by objects clearly without the aid of glasses or contacts, or when a second surgery might be required to further correct your near vision.

Bilateral Simultaneous Treatment
You may choose to have LASIK surgery on both eyes at the same time or to have surgery on one eye at a time. Although the convenience of having surgery on both eyes on the same day is attractive, this practice is riskier than having two separate surgeries. The second eye may have a higher risk of developing an inflammation if surgery is done on the same day than if surgery is performed on separate days. If a malfunction of the laser or microkeratome occurs causing a complication with the first eye, the second eye is more likely to also experience the same complication if the surgery is performed on the same day rather than on separate days.

If you decide to have one eye done at a time, you and your doctor will decide how long to wait before having surgery on the other eye. If both eyes are treated at the same time or before one eye has a chance to fully heal, you and your doctor do not have the advantage of being able to see how the first eye responds to surgery before the second eye is treated.

Another disadvantage to having surgery on both eyes at the same time is that the vision in both eyes may be blurred after surgery until the initial healing process is over, rather than being able to rely on clear vision in at least one eye at all times.

Finding the Right Doctor:-

If you are considering refractive surgery, make sure you:

*Compare. The levels of risk and benefit vary slightly not only from procedure to procedure, but from device to device depending on the manufacturer, and from surgeon to surgeon depending on their level of experience with a particular procedure.

*Don’t base your decision simply on cost and don’t settle for the first eye center, doctor, or procedure you investigate. Remember that the decisions you make about your eyes and refractive surgery will affect you for the rest of your life.

*Be wary of eye centers that advertise, “20/20 vision or your money back” or “package deals.” There are never any guarantees in medicine.

Read. It is important for you to read the patient handbook provided to your doctor by the manufacturer of the device used to perform the refractive procedure. Your doctor should provide you with this handbook and be willing to discuss his/her outcomes (successes as well as complications) compared to the results of studies outlined in the handbook. Even the best screened patients under the care of most skilled surgeons can experience serious complications.

During surgery. Malfunction of a device or other error, such as cutting a flap of cornea through and through instead of making a hinge during LASIK surgery, may lead to discontinuation of the procedure or irreversible damage to the eye.
After surgery. Some complications, such as migration of the flap, inflammation or infection, may require another procedure and/or intensive treatment with drops. Even with aggressive therapy, such complications may lead to temporary loss of vision or even irreversible blindness.
Under the care of an experienced doctor, carefully screened candidates with reasonable expectations and a clear understanding of the risks and alternatives are likely to be happy with the results of their refractive procedure.

Advertising
Be cautious about “slick” advertising and/or deals that sound “too good to be true.” Remember, they usually are. There is a lot of competition resulting in a great deal of advertising and bidding for your business. Do your homework.

What should you expect before, during, and after surgery ?
What to expect before, during, and after surgery will vary from doctor to doctor and patient to patient. This section is a compilation of patient information developed by manufacturers and healthcare professionals, but cannot replace the dialogue you should have with your doctor. Read this information carefully and with the checklist, discuss your expectations with your doctor.

Before Surgery
If you decide to go ahead with LASIK surgery, you will need an initial or baseline evaluation by your eye doctor to determine if you are a good candidate. This is what you need to know to prepare for the exam and what you should expect:

If you wear contact lenses, it is a good idea to stop wearing them before your baseline evaluation and switch to wearing your glasses full-time. Contact lenses change the shape of your cornea for up to several weeks after you have stopped using them depending on the type of contact lenses you wear. Not leaving your contact lenses out long enough for your cornea to assume its natural shape before surgery can have negative consequences. These consequences include inaccurate measurements and a poor surgical plan, resulting in poor vision after surgery. These measurements, which determine how much corneal tissue to remove, may need to be repeated at least a week after your initial evaluation and before surgery to make sure they have not changed, especially if you wear RGP or hard lenses.

If you wear:
*soft contact lenses, you should stop wearing them for 2 weeks before your initial evaluation.
*toric soft lenses or rigid gas permeable (RGP) lenses, you should stop wearing them for at least 3 weeks before your initial evaluation.
*hard lenses, you should stop wearing them for at least 4 weeks before your initial evaluation.

You should tell your doctor:
*about your past and present medical and eye conditions
*about all the medications you are taking, including over-the-counter medications and any medications you may be allergic to

Your doctor should perform a thorough eye exam and discuss:
*whether you are a good candidate
*what the risks, benefits, and alternatives of the surgery are
*what you should expect before, during, and after surgery
*what your responsibilities will be before, during, and after surgery

You should have the opportunity to ask your doctor questions during this discussion. Give yourself plenty of time to think about the risk/benefit discussion, to review any informational literature provided by your doctor, and to have any additional questions answered by your doctor before deciding to go through with surgery and before signing the informed consent form.

You should not feel pressured by your doctor, family, friends, or anyone else to make a decision about having surgery. Carefully consider the pros and cons.

The day before surgery, you should stop using:

*creams
*lotions
*makeup
*perfumes

These products as well as debris along the eyelashes may increase the risk of infection during and after surgery. Your doctor may ask you to scrub your eyelashes for a period of time before surgery to get rid of residues and debris along the lashes.

Also before surgery, arrange for transportation to and from your surgery and your first follow-up visit. On the day of surgery, your doctor may give you some medicine to make you relax. Because this medicine impairs your ability to drive and because your vision may be blurry, even if you don’t drive make sure someone can bring you home after surgery.

During Surgery:-
The surgery should take less than 30 minutes. You will lie on your back in a reclining chair in an exam room containing the laser system. The laser system includes a large machine with a microscope attached to it and a computer screen.

A numbing drop will be placed in your eye, the area around your eye will be cleaned, and an instrument called a lid speculum will be used to hold your eyelids open. A ring will be placed on your eye and very high pressures will be applied to create suction to the cornea. Your vision will dim while the suction ring is on and you may feel the pressure and experience some discomfort during this part of the procedure. The microkeratome, a cutting instrument, is attached to the suction ring. Your doctor will use the blade of the microkeratome to cut a flap in your cornea.

The microkeratome and the suction ring are then removed. You will be able to see, but you will experience fluctuating degrees of blurred vision during the rest of the procedure. The doctor will then lift the flap and fold it back on its hinge, and dry the exposed tissue.

The laser will be positioned over your eye and you will be asked to stare at a light. This is not the laser used to remove tissue from the cornea. This light is to help you keep your eye fixed on one spot once the laser comes on. NOTE: If you cannot stare at a fixed object for at least 60 seconds, you may not be a good candidate for this surgery.

When your eye is in the correct position, your doctor will start the laser. At this point in the surgery, you may become aware of new sounds and smells. The pulse of the laser makes a ticking sound. As the laser removes corneal tissue, some people have reported a smell similar to burning hair. A computer controls the amount of laser delivered to your eye. Before the start of surgery, your doctor will have programmed the computer to vaporize a particular amount of tissue based on the measurements taken at your initial evaluation. After the pulses of laser energy vaporize the corneal tissue, the flap is put back into position.

A shield should be placed over your eye at the end of the procedure as protection, since no stitches are used to hold the flap in place. It is important for you to wear this shield to prevent you from rubbing your eye and putting pressure on your eye while you sleep, and to protect your eye from accidentally being hit or poked until the flap has healed.

After Surgery:-
Immediately after the procedure, your eye may burn, itch, or feel like there is something in it. You may experience some discomfort, or in some cases, mild pain and your doctor may suggest you take a mild pain reliever. Both your eyes may tear or water. Your vision will probably be hazy or blurry. You will instinctively want to rub your eye, but don’t! Rubbing your eye could dislodge the flap, requiring further treatment. In addition, you may experience sensitivity to light, glare, starbursts or haloes around lights, or the whites of your eye may look red or bloodshot. These symptoms should improve considerably within the first few days after surgery. You should plan on taking a few days off from work until these symptoms subside. You should contact your doctor immediately and not wait for your scheduled visit, if you experience severe pain, or if your vision or other symptoms get worse instead of better.

You should see your doctor within the first 24 to 48 hours after surgery and at regular intervals after that for at least the first six months. At the first postoperative visit, your doctor will remove the eye shield, test your vision, and examine your eye. Your doctor may give you one or more types of eye drops to take at home to help prevent infection and/or inflammation. You may also be advised to use artificial tears to help lubricate the eye. Do not resume wearing a contact lens in the operated eye, even if your vision is blurry.

You should wait one to three days following surgery before beginning any non-contact sport
s, depending on the amount of activity required, how you feel, and your doctor’s instructions.

To help prevent infection, you may need to wait for up to two weeks after surgery or until your doctor advises you otherwise before using lotions, creams, or make-up around the eye. Your doctor may advise you to continue scrubbing your eyelashes for a period of time after surgery. You should also avoid swimming and using hot tubs or whirlpools for 1-2 months.

Strenuous contact sports such as boxing, football, karate, etc. should not be attempted for at least four weeks after surgery. It is important to protect your eyes from anything that might get in them and from being hit or bumped.

During the first few months after surgery, your vision may fluctuate.
*It may take up to three to six months for your vision to stabilize after surgery.
*Glare, haloes, difficulty driving at night, and other visual symptoms may also persist during this stabilization period. If further correction or enhancement is necessary, you should wait until your eye measurements are consistent for two consecutive visits at least 3 months apart before re-operation.
*It is important to realize that although distance vision may improve after re-operation, it is unlikely that other visual symptoms such as glare or haloes will improve.
*It is also important to note that no laser company has presented enough evidence for the FDA to make conclusions about the safety or effectiveness of enhancement surgery.

Contact your eye doctor immediately, if you develop any new, unusual or worsening symptoms at any point after surgery. Such symptoms could signal a problem that, if not treated early enough, may lead to a loss of vision.

Resources:
http://www.medicinenet.com/script/main/art.asp?articlekey=83884
http://en.wikipedia.org/wiki/LASIK