What Is Refractive Surgery?

If you have a refractive error, such as  nearsightedness  (myopia), farsightedness (hyperopia), astigmatism or presbyopia refractive surgery is a method for correcting or improving your vision. There are various surgical procedures for correcting or adjusting your eye’s focusing ability by reshaping the cornea, or clear, round dome at the front of your eye. Other procedures involve implanting a lens inside your eye. The most widely performed type of refractive surgery is LASIK (laser-assisted in situ keratomileusis), where a laser is used to reshape the cornea.

For people who are nearsighted, certain refractive surgery techniques will reduce the curvature of a cornea that is too steep so that the eye’s focusing power is lessened. Images that are focused in front of the retina, due to a longer eye or steep corneal curve, are pushed closer to or directly onto the retina following surgery.

Farsighted people will have refractive surgery procedures that achieve a steeper cornea to increase the eye’s focusing power. Images that are focused beyond the retina, due to a short eye or flat cornea, will be pulled closer to or directly onto the retina after surgery.

Astigmatism can be corrected with refractive surgery techniques that selectively reshape portions of an irregular cornea to make it smooth and symmetrical. The result is that images focus clearly on the retina rather than being distorted due to light scattering through an irregularly shaped cornea.

Refractive surgery might be a good option for you if you:

• Want to decrease your dependence on glasses or contact lenses;
• Are free of eye disease;
• Accept the inherent risks and potential side effects of the procedure;
• Understand that you could still need glasses or contacts after the procedure to achieve your best vision;
• Have an appropriate refractive error.

There is no universally-accepted, best method for correcting refractive errors. The best option for you should be decided after a thorough examination and discussion with your ophthalmologist. If you are considering refractive surgery, you and your Eye Surgeon. can discuss your lifestyle and vision needs to determine the most appropriate procedure for you.

(Source material from American academy of ophthalmology)

LASIK — Laser Eye Surgery

LASIK (laser-assisted in situ keratomileusis) is an outpatient refractive surgery procedure used to treat nearsightedness, farsightedness and astigmatism. A laser is used to reshape the cornea — the clear, round dome at the front of the eye — to improve the way the eye focuses light rays onto the retina at the back of the eye.

With LASIK, an ophthalmologist creates a thin flap in the cornea using either a blade or a laser. The surgeon folds back the flap and precisely removes a very specific amount of corneal tissue under the flap using an excimer laser. The flap is then laid back into its original position where it heals in place.

For people who are nearsighted, LASIK is used to flatten a cornea that is too steep. Farsighted people will have LASIK to achieve a steeper cornea. LASIK can also correct astigmatism by shaping an irregular cornea into a more normal shape.

It is important that anyone considering LASIK have realistic expectations. LASIK allows people to perform most of their everyday tasks without corrective lenses. However, people looking for perfect vision without glasses or contacts run the risk of being disappointed. More than 90 percent of people who have LASIK achieve somewhere between 20/20 and 20/40 vision without glasses or contact lenses. If sharp, detailed 20/20 vision is essential for your job or leisure activities, consider whether 20/40 vision would be good enough for you.

You should be comfortable with the possibility that you may need a second surgery (called a retreatment or enhancement) or that you might need to wear glasses for certain activities, such as reading or driving at night. Also, you should be aware that LASIK cannot correct presbyopia, the age-related loss of close-up focusing power.

(Source material from American academy of ophthalmology)

How the LASIK procedure works

LASIK is performed while the patient reclines under a surgical device called an Excimer laser in an outpatient surgical suite. First, the eye is numbed with a few drops of topical anesthetic. An eyelid holder is placed between the eyelids to keep them open and prevent the patient from blinking. A suction ring placed on the eye lifts and flattens the cornea and helps keep the eye from moving. The patient may feel pressure from the eyelid holder and suction ring, similar to a finger pressed firmly on the eyelid.

From the time the suction ring is put on the eye until it is removed, vision appears dim or goes black. Once the cornea is flattened, a hinged flap of corneal tissue is created using an automated microsurgical device, either a laser or blade. This corneal flap is lifted and folded back. Then the excimer laser preprogrammed with the patient’s unique eye measurements is centered above the eye.

The surgeon checks that the laser is positioned correctly. The patient looks at a special pinpoint light, called a fixation or target light, while the excimer laser sculpts the corneal tissue. Then the surgeon places the flap back into position and smoothes the edges. The corneal flap sticks to the underlying corneal tissue within two to five minutes, and stitches are not needed.

The patient should plan to have someone drive him or her home after the procedure and then take a nap or just relax. To help protect the cornea as it heals, the surgeon may place a transparent shield over the eye(s) to protect against accidental bumps and to remind the patient not to rub the eye(s). The patient may need to wear the shield only when sleeping. The surgeon will provide eyedrops to help the eye heal and relieve dryness.

It may take three to six months after LASIK surgery for the improvements in a person’s vision to fully stabilize and any side effects to go away.

(Source material from American academy of ophthalmology)  

Alternative refractive Surgery Procedures

Today’s refractive surgery options for vision correction range from corneal reshaping with lasers to surgical insertion of artificial lenses. Following are some of the alternative refractive surgery procedures to LASIK.

Wavefront-Guided LASIK

Before surgery, the excimer laser is programmed with each patient’s wavefront data to prepare it to perform a very precise “sculpting” of each unique cornea. In conventional LASIK, this programming is based on the patient’s vision correction prescription (the same as used for the patient’s glasses or contacts.)

In wavefront-guided LASIK, computer imaging technology creates a very detailed three-dimensional “map” of the patient’s cornea that looks a bit like a miniature mountain range. This “map” is used to program the excimer laser for surgery. Wavefront technology can measure very subtle abnormalities in the surface of the cornea, enabling wavefront-guided LASIK to achieve vision correction beyond what is possible with glasses or conventional LASIK.

Also, wavefront LASIK has been shown in several studies to reduce side effects, such as problems with night vision and contrast sensitivity (the ability to clearly see objects against a background, such as black letters on a white page), and also to increase the percentage of patients who achieve 20/20 vision. Wavefront technology may also be used in PRK procedures, for similar reasons and with similar results.

PRK: Another Path to Laser Vision Correction

Photorefractive keratectomy (PRK) uses the excimer laser in the same way as LASIK, and patients’ vision correction results are similar. The main difference between PRK and LASIK is that in PRK there is no flap — only the very top (epithelial) layer of the cornea is removed (or moved aside) before the excimer laser sculpts the cornea.

Many PRK surgeons use a blunt, gently vibrating microkeratome to remove the epithelial layer. LASEK and Epi-LASIK, described below, are other PRK techniques. New approaches, such as advanced surface ablation in which the cornea is cooled either before or after surgery, help reduce the discomfort that may occur after PRK. The patient may also be given topical antibiotics and anti-inflammatory medications and oral pain medications to reduce discomfort and speed healing after surgery. A “bandage” soft contact lens is used to promote epithelial healing, which takes about four days.

While LASIK patients often report clear, improved vision by the day after surgery, it may be a few days before vision stabilizes for PRK patients. The cornea’s epithelial layer re-grows during this time. The thicker corneal flap created in LASIK is not made in PRK, so if there is a concern about potential flap complications, the surgeon may recommend PRK. If the patient’s corneas are too thin to meet LASIK standards, if he or she had LASIK previously, or if other eye health factors are involved, the surgeon and patient may decide that PRK would be a better choice.

Wavefront-guided PRK offers additional vision correction, similar to wavefront-guided LASIK. Though thousands of wavefront-guided PRK procedures have been safely and effectively performed in the United States, the FDA approval process has not yet taken place, so wavefront-guided PRK is considered an “off-label” use of the technology. Professional medical standards permit Eye M.D.s to use this and other “off-label” procedures and medications.

LASEK

A microsurgical instrument called a trephine is used to create a flap of epithelial corneal tissue, and an alcohol solution is used to loosen the epithelial cells. Once the epithelial flap is created and moved aside, the procedure is the same as PRK. After corneal sculpting, the epithelial flap is repositioned and smoothed with a small spatula, then secured with a “bandage” soft contact lens to promote epithelial healing, which takes about four days.

EpiLasik

A special microkeratome, the Epi-keratome, is used to precisely separate a very thin sheet of epithelial tissue from the cornea. This thin sheet is lifted to the side and the cornea is treated as with PRK. Then the thin sheet may be moved back into place to re-adhere to the cornea or removed. A “bandage” soft contact lens is applied and used for about four days to help the epithelial layer heal.

Conductive Keratoplasty (CK)

CK is a noninvasive, thermal refractive surgery procedure used to correct mild to moderate farsightedness (hyperopia) in people over age 40. With CK, your Eye M.D. uses a tiny probe that releases controlled amounts of radio frequency (RF) energy, instead of a laser, to apply heat to the peripheral portion of the cornea. The heat then causes the peripheral cornea to shrink and tighten like a belt. This increases the curvature (steepness) of the central cornea, improving the optical power of the central cornea. This refocuses light rays on the retina and enhances vision.

CK can be used to achieve “monovision” (blended vision). With monovision, CK can be used to improve close-up vision in a presbyopic eye with good vision but poor near focus. To maintain good distance vision, usually only one eye is set to near focus (the non-dominant eye), while the other is left or set at good distance vision. CK does not offer permanent correction; for some people, farsightedness may return over time.

Phakic Intraocular Lenses (IOLs)

Phakic IOLs are designed for people with high degrees of refractive errors that cannot be safely corrected with corneal-based refractive surgery. The phakic IOL, sometimes referred to as an implantable contact lens, or ICL, is surgically implanted inside the eye in front of the eye’s natural lens. The eye’s natural lens is not removed, so patients can retain their pre-existing ability to focus.

During the phakic IOL procedure, your Eye M.D. places the phakic IOL either in front of or behind the iris of the eye. Once the IOL is properly positioned inside the eye, it provides the necessary correction to redirect light rays precisely onto the retina.

Refractive Lens Exchange (Clear Lens Extraction)

With refractive lens exchange (RLE) — also called Clear Lens Extraction or CLE — an artificial lens is used to replace your eye’s natural lens in order to improve vision. The procedure is performed much like cataract surgery.

As is an option in cataract surgery, RLE may employ multifocal or accommodative intraocular lenses (IOLs). These lenses allow the ability to focus at all distances.

Some people who have early stage cataracts may choose to have RLE instead of waiting for their cataracts to progress to the point where they should be removed. This is because the lens implants generally provide them with better uncorrected vision at that point, particularly if they currently need vision correction.

RLE may also be an option for people with severe hyperopia (farsightedness), for whom LASIK is not recommended.

Laser Surgery Recovery

How long does it take to heal after laser eye surgery?

One of the benefits of correcting refractive errors with laser surgery is that, in most cases, recovery is relatively quick.

Immediately after LASIK, LASEK, or other similar procedures that create a replaceable flap in your cornea, your eye begins to heal. The day after your surgery, your eye surgeon or other eye doctor will test your vision and check to see that your eyes are healing as they should. In most cases, you can return to work, as well as drive, the day after the procedure.

If you have had PRK, healing may take a little longer. This is because a thin, outer layer of corneal cells is removed (rather than replaced as a flap like with LASIK or LASEK). The cells grow back, but it takes a few days after surgery to do so. This will delay the amount of time it takes to comfortably and safely get back to working and driving.

For several weeks or even months after laser eye surgery, it is normal to have some blurry vision or notice your vision changing. You may also have dry eyes, or see glare or halos around lights.

For six months or longer after laser surgery, you will probably be scheduled for regular follow-up visits with your eye doctor to check how your eyes are doing. In most cases, vision is stable and clear at about six months after surgery. If you had dry eyes or other visual disturbances after surgery, you should find most of these symptoms have disappeared or are much less obvious.

Past the six-month point after laser eye surgery, if you still have vision issues, your ophthalmologist may recommend another laser surgery procedure—called an enhancement—to fine tune your eyesight.

(Source material from American academy of ophthalmology)