Corrective Eye Surgery

Corrective Eye Surgery Basics

Until contact lenses were popularized in the 1950s, eyeglasses for at least the past seven centuries had been the only practical way to correct refractive vision errors. Now, several modern approaches to corrective eye surgery range from laser reshaping of the eye's surface in procedures such as LASIK and PRK to surgical insertion of artificial lenses to correct eyesight. In LASIK, PRK, and similar procedures, laser energy reshapes the curvature of the eye's clear front surface (cornea) to alter the way light rays enter the eye. Artificial lenses surgically inserted into the eye also can refocus light rays to sharpen vision.

The Evolution of Corrective Eye Surgery

Over the past 25 years, surgical techniques, tools, and procedures for vision correction have evolved rapidly.

Radial Keratotomy (RK), used in the United States primarily during the 1980s, involved cutting spoke-like incisions to flatten the eye's surface mainly to correct nearsightedness. But results, especially long-term, created problems for some individuals. Significant glare, regression, fluctuating vision, and other side effects such as night vision problems were common in patients who had RK for higher prescription strengths, while such side effects were less frequent in patients with lower prescriptions. RK is now virtually obsolete as a primary vision correction procedure for these reasons and because of advances in laser vision correction procedures.

Photorefractive Keratectomy (PRK) was the first successful laser vision correction procedure used to remove (ablate) tissue directly from the eye's surface to change the curvature of the cornea. PRK, also known as surface ablation, was performed outside the United States during the 1980s and received U.S. Food and Drug Administration approval in 1995. PRK is still commonly used, but LASIK (see below) is by far the most popular laser procedure today.

However, PRK has made somewhat of a comeback in recent years because of studies indicating that PRK and LASIK produce similar outcomes. Also, nerve regeneration in the eye's surface appears to take place faster with PRK than with LASIK following a procedure, which could have implications for reducing dry eye and other complications that might occur until the healing process is complete. Because PRK is a surface procedure, there is also no risk of surgical flap complications. PRK does not involve creating a thin, hinged flap on the eye's surface, as occurs with LASIK. PRK also appears to be a safer procedure in cases when a person's cornea may be too thin for LASIK surgery.

Laser-Assisted in situ Keratomileusis (LASIK) is like PRK, except that a thin, hinged flap is made in the eye's surface. This flap is lifted, and then laser energy is applied underneath to reshape the eye. The flap is replaced and functions as a natural bandage. LASIK's main advantage over PRK is that there is little or no discomfort immediately after the procedure, and vision is usually clear within hours rather than days. Different forms of LASIK exist, many that depend on how the flap is created:

• LASEK involves creating an ultra-thin hinged flap in the thin outer covering (epithelium) of the eye and floating it away from the eye's surface with alcohol so that laser reshaping of the eye can occur.


• Epi-LASIK is like LASEK, except that a special cutting tool is used to lift the flap. This eliminates the possibility of an adverse reaction to alcohol placed on the eye's surface during LASEK.


• Bladeless, Blade-Free, or All-Laser LASIK involves use of another laser rather than a mechanical cutting tool to create the flap in LASIK. Because the laser used for this purpose originally was made and marketed by IntraLase Corp., all-laser LASIK was sometimes also called IntraLASIK. In 2007, Advanced Medical Optics obtained the IntraLase technology and integrated it into the company's CustomVue excimer laser platform (iLASIK).


• Wavefront LASIK or PRK (also known as wavefront-guided, wavefront-assisted, or custom LASIK/PRK) incorporates ultra-modern analysis, known as wavefront, to measure precisely how light travels through the eye. Excimer lasers with built-in wavefront analysis can detect and automatically adjust for subtle vision errors when laser energy is applied to reshape the cornea. Studies suggest wavefront-guided LASIK reduces the risk of night glare after LASIK surgery, explained in our Q&A about custom LASIK.

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