Wavefront-Guided LASIK: a Recent Advance

Before surgery, the excimer laser is programmed with each patient’s 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.

Beyond LASIK: Other Laser Procedures

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 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 MDs 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.

Some of this information is used with permission from the EyeCare America Web site: www.eyecareamerica.org/eyecare/treatment/lasik/index.cfm. Accessed April 9, 2008.

Last reviewed and updated in February 2009,
by the American Academy of Ophthalmology.