Glasses, contact lenses and refractive surgeries treat refractive errors. Glasses and contact lenses do so by bending light rays before they pass through the cornea. Most refractive surgeries correct vision by altering the shape of the cornea itself.

Refractive surgery has been available for over 100 years, but was not effective until the 1970s when radial keratotomy was developed. This procedure used spoke-shaped incisions to alter the corneal curvature. However, in the 1980s, the excimer laser revolutionized the world of refractive surgery. Laser vision correction is a proven new method of improving vision. Corneal surgeons are able to correct the most commonly occurring refractive errors using leading edge laser technology.

LASIK
The most popular and widely accepted method of laser vision correction is Laser in-Situ Keratomileusis, usually called LASIK. Nicknamed "flap and zap", this is a two-stage surgery. In the first part, the surgeon uses a sophisticated instrument known as a microkeratome to cut horizontally across 90% of the cornea. In LASIK surgery performed with the Intralase FS, the flap is created by the use of this specialized laser. This creates a thin flap that is gently folded away from the central cornea so it can be re-shaped with the excimer laser. The excimer laser works with great precision, removing tissue micron by micron from the internal layers of the cornea. Once the laser has finished sculpting the cornea, the flap is carefully returned to its original position. No stitches are necessary because the cornea has remarkable adherent qualities and begins to heal quickly after the surgery.

LASIK for Myopia
LASIK has seen its greatest success in correcting myopia. During a LASIK surgery for myopia, the excimer laser removes tissue from the center of the cornea, thereby reducing its curvature and improving its ability to focus light onto the retina. LASIK can effectively treat low, moderate and high levels of myopia.

LASIK for Hyperopia
LASIK has also proven successful in reducing low to moderate levels of hyperopia. In these procedures, the excimer laser removes tissue from the corneal periphery, thereby increasing the curvature of the cornea and improving its focusing ability.

LASIK for Astigmatism
LASIK can also be used to correct astigmatism, either on its own or in tandem with corrections for myopia or hyperopia. In astigmatic eyes, the excimer laser is programmed to remove more tissue from some regions of the cornea than others, thus creating a more spherical surface.

LASIK & Presbyopia
LASIK cannot cure presbyopia or make reading glasses obsolete. Fortunately, monovision gives some people another option for managing their presbyopia. With the monovision option, one eye is corrected for distance vision and the other is corrected for near vision. The advantage of monovision is that many people can achieve a broader range of functional vision without reading glasses. However, a significant number of people have difficulty adjusting to monovision and may experience balance difficulties or impaired depth perception. Anyone who wants monovision should try it with contact lenses or glasses before surgery. If surgically created monovision is unsatisfactory an enhancement can be performed later to correct the near vision eye to the same degree as the eye corrected for distance vision.

" I have monovision. I had to have a retreatment because I had some regression, so I retreated one eye and it's about 20/20. The other eye is less than that, but it's the one I read with. I automatically adjust. If I am reading the left eye kicks in; if I'm not, the right works. It's really perfect for me." - Linda B.

Other Refractive Surgeries
Although LASIK is the most common refractive surgery performed for most people there are occasions when other surgical methods may be more suitable.

PRK
PRK (Photorefractive Keratectomy) is the original excimer laser vision correction procedure. Since it was developed in the late 1980s, over one million PRK surgeries have been performed worldwide. PRK differs from LASIK in that no flap is made. The surgeon simply removes the cornea's outermost epithelial cell layer. The excimer laser then removes microscopic amounts of tissue from the corneal surface. PRK is effective at correcting low to moderate levels of myopia, but vision can take up to six months to stabilize and pain or discomfort are more common post-operatively than with LASIK.

LASIK surgery is a two-step process. First, the surgeon must gain access to your cornea by creating a flap of tissue. The tissue is then folded back and the surgeon is able to perform laser vision correction treatment on the inner layer of the cornea.

Traditionally, the surgeon has created the corneal flap with a hand-held mechanical device (known as a microkeratome), which utilizes a surgical blade. This method has worked well over the years; however, the performance of these devices can be unpredictable. And although LASIK complications are rare, this mechanical device is frequently the source for many of the reported complications.

With the IntraLase laser, the surgeon uses the precision of a laser to create the corneal flap. The accuracy of the laser (100 times more accurate than a blade) is unparalleled by any other technology in vision correction surgery. This advanced technology allows the surgeon more control during the procedure, and even allows customization of the corneal flap for every individual patient. Because of its consistent accuracy, IntraLase now makes it possible to treat many patients who were dismissed as candidates for laser vision correction due to thin corneas.

The IntraLase FS laser uses infrared light to precisely cut tissue by a process known as photodisruption. Specialized software directs the process of focusing the laser beam into a tiny, 2-3 micron spot of energy. The beam passes harmlessly through the outer layers of the cornea until it reaches its exact focal point within the central part of the cornea (known as the stroma). Upon reaching this focal point, the beam forms a microscopic bubble of carbon dioxide and water vapor. Thousands of these bubbles are placed at a precisely controlled depth to define a dissection plane. By using the rapidly fired IntraLase laser and interconnecting the bubbles very tightly the surgeon can create a corneal flap with remarkable precision and accuracy.

IntraLase is Uniquely Safe
LASIK performed with a mechanical microkeratome has produced excellent results with few complications. However, the IntraLase laser has further reduced potential surgical/LASIK complications - specifically, the IntraLase allows for fewer case interruptions and fewer abnormally thick or thin flaps. IntraLase also helps preserve specified amounts of corneal tissue.

IntraLase is Uniquely Accurate
One of the key features of the IntraLase FS laser is its ability to create flaps of a specified thickness. Numerous studies have demonstrated that the thickness of flaps created with the IntraLase are significantly more precise than those created with a mechanical microkeratome. This precision allows surgeons to more accurately plan your surgery.

Predictably Better Vision
Numerous national studies have demonstrated the ability of the IntraLase FS laser to deliver better visual outcomes than those achievable with mechanical microkeratome LASIK. Specifically, it has been shown that the IntraLase delivers superior post-operative visual acuity and an overall reduction in higher-order aberrations.

In qualified hands, LASIK and other vision correction procedures are extremely safe, with complications occurring only rarely. However, complications do occur and you should be aware of their possibility before undergoing surgery. Some of the potential downsides of LASIK can include:

• Flap Complications: In a very few cases, the corneal flap may wrinkle or shift shortly after surgery. These problems occur in less than 1% of LASIK cases at Casey Vision Correction Center. The problem may resolve on its own, or the surgeon may gently smooth or straighten the flap. In some cases, a bandage contact lens may be needed for a brief period. Other potential flap complications include infection and debris or inflammation under the flap. These complications are very rare. If these problems occur, they can usually be quickly treated with the appropriate eye drops.
• Corneal haze: Fewer than 2% of PRK patients and 0.5% of LASIK patients experience corneal haze. Haze is most noticeable at night and usually peaks two to three months after surgery. In many cases, the haze is unnoticed by the patient and is only observed by the doctor during an eye exam. In most patients, the haze clears up on its own within a year. Rarely, the surgeon will recommend an enhancement to reduce haze.
• Dry Eyes: Some people may experience dry eyes temporarily after surgery, although in a few cases it may become a long-term problem. Dry eyes may feel scratchy, itchy, irritated, or even watery, but the discomfort can usually be relieved with a type of eye drop known as artificial tears. If artificial tears do not solve the problem, small silicone plugs called punctal plugs can be gently placed in the ducts through which moisture drains from the eye. Punctal plugs are usually only needed for a brief period, but may occasionally be a long-term solution. People who have dry eyes before surgery are more likely to experience dry eye problems afterwards.
• Under-Correction or Over-Correction: Although most LASIK patients achieve the targeted refraction, the occasional person may have an unusually aggressive or unusually weak healing response. In these cases, the eye can be under- or over-corrected. Once the healing process is complete and vision has stabilized, the doctor assesses the eye's refraction: if myopia of one diopter or more remains at that time, the surgeon may recommend an enhancement.

Although not technically considered as risks of refractive surgery, the following potential problems should be considered by anyone contemplating refractive surgery.

Impaired Night Vision: Recent media reports suggested a link between LASIK and reduced night vision. However, these were based on an English study that used old lasers on patients requiring high levels of correction. The vast body of evidence from studies conducted at world-recognized refractive laser centers demonstrates an incidence rate of less than 2%. In most cases, these effects are not troublesome. It should be noted that night vision problems after LASIK are linked to factors such as large pupil size, unusually flat corneas or the use of a laser with a small treatment zone. Checking for factors, which would pre-dispose someone to night vision problems is a routine part of a pre-operative exam. Excimer lasers can be programmed to treat larger optical zones thus minimizing the incidence of night vision problems.

Possibly needing corrective lenses. No refractive surgery can promise everyone perfect results and no reputable surgeon will make such a guarantee. Every eye has its own unique healing pattern and the occasional person may not heal as expected. In these cases, glasses may be needed for activities such as driving or watching television. In general, the more severe the focusing problem before surgery, the greater the likelihood that an enhancement may be appropriate or that glasses may be needed occasionally after surgery.

Needing reading glasses. No eye surgery can prevent presbyopia, so if you already need reading glasses or bifocals, you will still require reading glasses after surgery. If you are in your twenties or thirties, reading glasses will probably become necessary in the next few decades. For some people, monovision (different levels of correction for each eye) may be a viable alternative.

CustomCornea LASIK is a new type of refractive surgery. During this procedure sophisticated diagnostic data is used from a specialized instrument called a wavefront analyzer (known as LADARWave) to perform customized LASIK treatments. Essentially, this is a new technique for mapping the refractive errors in the eye. In the past, surgeons have used a topographical map to see just the surface of the cornea. With LADARWave, Alcon's measurement device, surgeons are now able to generate a three-dimensional map of the entire visual pathway of the eye, allowing us to see errors called "higher order aberrations."

The LADARWave device sends light rays into the eye. These light rays pass through the cornea and lens to the retina. From there, the light rays are bounced back through the eye. As they exit the eye, the LADARwave captures and measures their precise location. This data is then used to create a three-dimensional map of the eye's visual pathway. This map is like a fingerprint, because each person's is unique. The wavefront map is saved, analyzed by our physicians and used to guide the surgeon and the LADARVision excimer laser during the CustomCornea LASIK procedure.

Why does my doctor feel I should have CustomCornea LASIK instead of conventional LASIK?

Conventional LASIK is very successful at treating refractive errors on the corneal surface such as nearsightedness, farsightedness and astigmatism. However, some individuals have more complex refractive errors within their eyes called "higher order aberrations." These aberrations can cause visual distortions such as halos, glare or blurring, particularly at night. Higher order aberrations only occur in a visually significant manner (that is, to the extent that they noticeably affect vision) in 10% to 15% of the general population. In the past, some conventional LASIK patients with higher order aberrations have noticed visual side effects in their night vision. CustomCornea LASIK is designed to eliminate this problem. If your doctor has detected higher order aberrations within your eyes, he or she may recommend CustomCornea LASIK as the best option for you.

CustomCornea LASIK

• Goes beyond reshaping your cornea based on your eyeglass prescription. It is customized to your eyes
• Can detect and treat visual errors that could not previously be detected or treated
• May give you a better chance of achieving 20/20 vision or better after LASIK.
• May give you a reduced chance of losing visual quality or contrast sensitivity.
• May give you a reduced chance of night vision disturbances and glare.

This information provided by Casey Eye Institute, Oregon Health and Sciences University, 2005.