LASIK vs. LASEK: Spelling Error or Important Distinction?
LASIK and LASEK are very similar forms of laser eye surgery used to correct nearsightedness, farsightedness, astigmatism, and presbyopia. LASIK is an acronym for "Laser-Assisted In Situ Keratomileusis," while LASEK stands for "Laser-Assisted Sub-Epithelial Keratomileusis." The reference to "sub-epithelial" in LASEK's name gives the first clue to the differences between these two laser eye surgeries.
Epithelium
In LASEK, the epithelium, or outer layer of the cornea, is cut not with the microkeratome cutting tool used in LASIK, but with a finer blade called a trephine. Rather than entirely removing the epithelium (as is done in photorefractive keratectomy--PRK--surgery), LASEK attempts to save the epithelium by using an alcohol solution to cause the epithelial cells to weaken. LASEK surgery resembles LASIK surgery in that both involve the creation of a flap of the cornea, which can be put back in place at the end of the procedure. However, because it uses a thinner cutting instrument, the LASEK procedure can create this flap from just the epithelium, whereas LASEK involves deeper layers of the cornea.
When the epithelial layer has been moved out of the way, a laser alters the shape of the eye below, and then the epithelium is returned to its natural place. Sometimes when LASEK is attempted, the thin epithelium flap is too weak to be laid back in place. In these cases, the epithelium is removed, essentially turning the procedure into a PRK.
Results
Using the epithelium flap as a natural protective bandage with LASEK may improve healing and reduce the incidence of postoperative haze, when compared to PRK. Although all the epithelium is present immediately following LASEK, it needs time to become adherent. A smooth, central epithelium is crucial for clear vision. It normally takes three to ten days for the epithelium to heal and resurface the cornea.
Both LASEK and LASIK procedures have their pluses and minuses. LASEK recovery takes a few days longer than the recovery period for LASIK and may involve greater post-operative pain than LASIK, which is generally painless. On the other hand, LASEK has fewer post-operative haze problems than LASIK, perhaps because it preserves more corneal tissue than LASIK. Also, LASEK is less likely to result in dry eye issues than LASIK, and LASEK has fewer haze outcomes than LASIK.
Haze
Haze is a scar-like material in the cornea, caused by the cornea's wound response. The motivation behind LASEK was to find a surface ablation technique like PRK that induced less discomfort, offered a lower incidence of corneal haze, and provided the patient with faster vision recovery time. It is thought that using the epithelium flap as a natural protective bandage after LASEK (as opposed to completely removing the epithelium during PRK) may reduce postoperative haze.
A cornea's "healing haze," usually lasts for three to six months. The stronger the prescription being treated the greater the haze, and the more unpredictable the results. Haze involves the body laying down of tissue and thus results in a partial reversal of the treatment. The haze is not usually bad enough to impair vision, but can produce glare when driving at night. Even with LASEK, there may be a higher incidence of haze or cloudiness of the cornea for patients having very high degrees of nearsightedness (myopia).
Good Candidates
LASEK is a great option for patients previously turned down for LASIK because of thin or unusually shaped corneas or large pupils. LASEK is better for people with dry eye syndrome because it involves cutting such a thin flap that the corneal nerves that control our tearing reflex are left undamaged. LASEK is relatively new and is only performed by select laser vision correction surgeons, so candidates must have access to a surgeon experienced with the LASEK procedure and equipment.
