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Refractive Eye Correction

What is LASIK?

LASIK is a surgical procedure that can reduce a person's dependency on glasses or contact lenses. The procedure permanently changes the shape of the cornea (the delicate clear covering on the front of the eye). For clear vision, the eye's cornea and lens must bend (refract) light rays properly, so that images are focused on the retina. If the light rays aren't clearly focused on the retina, the images you see are blurry.

This blurriness is referred to as a "refractive error." It is caused by an imperfectly shaped eyeball, cornea, or lens. LASIK uses an Excimer Laser (an ultraviolet laser) to precisely remove corneal tissue to correct the shape for better focusing.

LASIK eye surgery is performed most often on people who have nearsightedness (myopia), which means that they only clearly see nearby objects; anything far away is blurry.

Review Date: 8/17/2007
Reviewed By: Manju Subramanian, MD, Assistant Professor in Ophthalmology, Vitreoretinal Disease and Surgery, Boston University Eye Associates, Boston, MA. Review provided by VeriMed Healthcare Network.


Photorefractive Keratectomy

Who benefits most?

  • People with low and moderate degrees of nearsightedness
  • People with low and moderate degrees of astigmatism

How PRK works?

This technique is the most simple and straightforward method of laser correction.


To perform PRK, the surgeon uses the excimer laser to vapourize away microscopic layers of tissue from the surface of the eye. By modifying the shape of the cornea, light rays can focus correctly within the eye to provide clear vision. PRK is less invasive than LASIK since only the surface tissue of the eye is affected.

For the procedure, the patient sits in a surgical chair which is reclined into a horizontal position. A surgical assistant instills topical anaesthetic drops on the eye to "freeze" it for a painless correction.

The cornea consists of different layers of tissue. The surface layer, known as the epithelium, is a soft, protective layer that regenerates quickly. Before laser correction, the surgeon removes this outer membrane by gently rubbing it away with an instrument. Within a few days of the surgery, the epithelium regenerates itself, again forming a protective layer over the eye.

The interior part of the cornea, known as the stroma, does not regenerate itself when removed. For PRK, the surgeon programs and positions the laser to remove a small portion of this stromal tissue to permanently change the shape of the cornea. In most cases, only 5 to 15% of the corneal thickness is treated, leaving the structural integrity of the cornea intact. The cool laser beam vapourizes tissue away, one microscopic layer at a time, without burning or cutting. Since the excimer laser light is created at a specified wavelength that does not pass through the cornea, no other part of the eye is affected.

To correct nearsightedness, the laser removes central tissue to reduce the curvature of the cornea so light rays will focus farther back and reach the retina. To correct astigmatism, the laser removes tissue from designated areas to equalize the curvatures of the cornea so light rays from the full scope of vision can focus evenly on the retina.

After the tissue has been removed, the surgeon places a special soft contact lens on the eye to protect it for the first few days of healing. This lens remains on the eye both day and night for up to four days, although it may be replaced on the second or third day.

The laser correction itself usually takes less than one minute per eye, although the patient is in the surgery suite for about 15 minutes.

LASIK Guidelines

The FDA, in cooperation with the American Academy of Ophthalmology, has developed the following guidelines and recommendations for good candidates for LASIK:

  • You should be at least 18 years old (21 for some lasers), since the vision of people younger than 18 usually continues to change. An exception is the small child with one very nearsighted and one normal eye. The use of LASIK to correct the very nearsighted eye may prevent amblyopia (lazy eye).
  • You should not be pregnant or nursing because these conditions might change the measured refraction of the eye.
  • You should not be taking certain prescription drugs, such as Accutane or oral prednisone.
  • Your eyes must be healthy and your prescription stable. If you're myopic, you should postpone LASIK until your refraction has stabilized, because myopia may continue to increase in some patients until their mid to late 20s.
  • You should be in good general health. LASIK may not be recommended for patients with diabetes, rheumatoid arthritis, lupus, glaucoma, herpes infections of the eye, or cataracts. You should discuss this with your surgeon.
  • Weigh the risks and rewards. If you're happy wearing contacts or glasses, you may want to forego the surgery.
  • Understand your expectations from the surgery. Are they realistic?
  • For patients with presbyopia, LASIK cannot correct so that one eye can see at BOTH distance and near. However, LASIK can be used to correct one eye for distance and the other for near. If you can adjust to this correction, it may eliminate or reduce your need for reading glasses. In some instances, surgery on only one eye is required. If your doctor thinks you're a candidate, ask about the pros and cons.
Review Date: 8/17/2007
Reviewed By: Manju Subramanian, MD, Assistant Professor in Ophthalmology, Vitreoretinal Disease and Surgery, Boston University Eye Associates, Boston, MA. Review provided by VeriMed Healthcare Network.

What is ICL?

Unlike traditional contact lenses the Implantable Collamer Lens (ICL) is surgically inserted in to the eye. The procedure is similar to Cataract surgery, but the natural lens of the eye is left in place. The ICL is implanted in front of the natural lens and works with it to correct vision, and provides one of the best postoperative results of all Refractive procedures available.

The Visian ICL offers unparalleled quality of vision.  Excellent for a wide range of vision correction needs. It is now possible to correct even very high prescriptions. The Visian ICL is the first lens of its kind to receive FDA approval for use in the US.  In clinical studies 99.4% of patients said that they were still satisfied three years after the procedure.


LASIK Recovery

  • It may take up to 3-6 months for vision to stabilize after surgery.
  • The most common complaints after LASIK are glare, haloes, and difficulty with night driving. Often, these problems will go away after 6 months, but a small percentage of people continue to complain about glare.
  • Sometimes additional surgery may be needed in order to get the best possible vision. These re-operations may be called "enhancement surgery." Generally, while the distance vision may improve with enhancement surgery, other visual symptoms such as glare or haloes may not.
  • The Academy of Ophthalmology (AAO) reports that of approximately 500,000 Americans who had LASIK surgery in 1999, 70% had 20/20 vision after surgery.
  • If your distance vision has been corrected with LASIK, it is likely that you may still need reading glasses around age 45.
  • The long-term effects of LASIK past 5 years after the surgery are yet to be determined.
Review Date: 8/17/2007
Reviewed By: Manju Subramanian, MD, Assistant Professor in Ophthalmology, Vitreoretinal Disease and Surgery, Boston University Eye Associates, Boston, MA. Review provided by VeriMed Healthcare Network.


Refractive Lensectomy

Who benefits most?

  • People with extreme degrees of nearsightedness or farsightedness, beyond what is easily corrected with laser corrective options.
  • People with signs of early cataract development
  • Most people over 60 years of age who are dependent on corrective lenses for distance vision

How refractive lensectomy works?

Unlike laser corrective surgeries which alter the shape of the cornea, a refractive lensectomy changes the focusing power of the lens within the eye. For this procedure, the eye's natural lens is removed and replaced by a manufactured lens implant which has been selected to provide clear focusing ability. The lens implant remains within the eye, without needing any further care after surgery. It provides a wide range of focusing freedom, but since it is a fixed focus lens, glasses are necessary for all near vision activities such as reading.

A refractive lensectomy is not generally recommended for people under 45 years of age, unless the diagnosis and careful testing reveals it to be the best option. People under 45 still have significant flexibility in their natural lens which allows them to vary their focus naturally. This ability is lost in a lensectomy procedure.

This ability is lost during the natural aging process, so those over 50 to 55 may not lose a significant amount of natural focusing flexibility through the procedure.

A refractive lensectomy is a simple outpatient procedure. Patients sit in a surgical chair, which is reclined back into a horizontal position. Attentive assistants ensure that patients are very comfortable as they drape them with sterile sheets in preparation for surgery.

Patients are not put to sleep, but they can be sedated with oral or intravenous medications, if necessary. Only the selected eye is "frozen" for this painless surgery. In most cases, topical drops are used to anaesthetize the eye, so no injection is necessary.

A refractive lensectomy procedure is similar to modern cataract surgery. To begin, the surgeon makes a small incision of 1/8 of an inch (2.8 mm) in either the white sclera or on the edge of the cornea. The surgeon inserts a delicate instrument to create a smooth, round opening in the outer capsule of the natural lens. Using an ultrasonic suction probe, the surgeon proceeds to gently break up and suction out the gel from the lens capsule. Then, the surgeon inserts a high quality lens implant of appropriate power and positions it securely within the natural lens capsule. Foldable lens implants are generally used. They are inserted through tiny incisions and then open up inside the eye where they are positioned to provide clear vision. For extremely high corrections, foldable lenses are not manufactured, so the incision is enlarged for the placement of a more rigid lens implant. The surgery is usually completed without stitches, since the incision is designed to be self-sealing. The whole procedure takes around 15 minutes.

Some lens implants can correct astigmatism. If needed, other surgical procedures can be combined with lens implantation to solve astigmatism focusing problems.