Potential Side Effects

More Common

Delayed epithelial healing is more typical of flapless procedures, such as PRK, LASEK and Epi-LASIK because they disturb a large area of epithelium, as opposed to flap procedures, which leave the epithelium intact.

Normally, the epithelium heals 3 to 5 days after a flapless procedure. During healing, the eyes are often scratchy and uncomfortable. A delay means that the discomfort lasts longer, and it also leads to an increased chance of haze.

Delayed epithelial healing can occur during a flap procedure if the epithelium is inadvertently disturbed during surgery.

Diffuse Lamellar Keratitis (DLK) refers to inflammation beneath a flap, so it is unique to LASIK and IntraLASIK and impossible with flapless procedures, such as PRK, LASEK and Epi-LASIK. Microscopically, DLK has a fine, white, sand-like appearance underneath the flap.

DLK almost always presents on the first postoperative day. Mild cases are treated with anti-inflammatory eye drops and daily follow-up until the inflammation begins to fade. With treatment, DLK usually peaks around day 3 to 6, gradually fades over the next few days and doesn't come back. For rare cases that don't respond adequately to drops, a return trip to the operating room to lift the flap and rinse away the inflammatory cells is the treatment of choice.

Dry eyes: Virtually all laser vision correction patients experience dry eyes. For most, the dryness is moderate for the first month, mild for the next few months and minimal after the third or fourth month. However, dryness varies widely and ranges from a dry sensation to filmy, fluctuating vision to continuously blurry vision and in rare instances on to painful, blurry vision.

The preoperative dryness level is the key predictor of postoperative dryness problems. A number of tests, such as the tear break-up time, fluorescein, lissamine green or rose bengal staining, Schirmer's test and biochemical tear analysis are used to quantify preoperative dryness. When preoperative dryness is severe, surgery is inadvisable.

The choice between a flap procedure such as LASIK or IntraLASIK and a flapless procedure, such as PRK, LASEK or Epi-LASIK, also affects postoperative dryness. In general, flap procedures lead to greater dryness, because formation of the flap interrupts more of the corneal nerves that are responsible for signaling the body to produce tears. These nerves eventually grow back, but the process takes anywhere from 6 months to 2 years. Flapless procedures still cause some dryness, because the laser treatment itself interrupts some of the corneal nerve fibers.

A number of treatments are available for dryness. The first line is artificial tear supplementation with products such as Systane, Refresh, GenTeal, Soothe, Thera-tears, Tears Naturale and others. If necessary, an ointment such as Refresh-PM, Akwa-tears or Lacrilube can be added at night.

When dryness remains a problem, the next step is often insertion of punctal plugs. These tiny plastic devices block the outflow of tears by plugging the tear drain in the corner of the eyelid near the nose. Though punctal plugs sound intimidating, they are easily and painlessly placed in a matter of seconds and work quite well for most patients.

As an alternative to plugs, some surgeons prefer Restasis, a prescription eye drop that increases natural tearing. Restasis doesn't help everyone, and it can take up to 6 months to work, but because it is the only available treatment that addresses the underlying problem behind the dryness, Restasis remains a popular choice.

Epithelial ingrowth is only a concern of the flap procedures, LASIK and IntraLASIK, and cannot occur with flapless surgery. For a flap to heal, the surface epithelium must seal along the margin where the flap was lifted. Occasionally, instead of just sealing, the epithelium migrates underneath the flap. Small amounts of ingrowth usually fade away with time, but large amounts necessitate lifting the flap and manually removing the excess epithelium.

Epithelial ingrowth almost never occurs with a first-time treatment, but it is a greater possibility when an existing flap is lifted for a retreatment. As more time passes between the initial treatment and the retreatment, epithelial ingrowth becomes more likely.

Although epithelial ingrowth is treatable, it can be frustrating because it occasionally recurs and necessitates another flap lift. For this reason, there is a slight trend toward retreating patients who are many years out from LASIK or IntraLASIK directly on the surface of the flap, as in PRK, rather than lifting the flap.

Flap striae are wrinkles in the flap, so they are unique to LASIK and IntraLASIK and cannot occur with flapless surgery. Microstriae are fine wrinkles that tend to occur with treatments for high levels of nearsightedness. Typically, they are not visually significant. Macrostriae are larger wrinkles that often form a concentric fingerprint-like pattern. Macrostriae are often caused by inadvertent rubbing or trauma early in the postoperative course and are treated by lifting the flap and smoothing the wrinkles.

Glare and halos around lights at night are already a fact of life for many patients who wear glasses and contact lenses. However, laser vision correction can worsen these complaints or cause them to develop in previously unaffected eyes.

Unfortunately, no preoperative test can determine with certainty whether glare and halo problems will develop. For many years, pupil size was thought to be a predictive factor, but a number of studies have failed to support a relationship between pupil size and night vision complaints. However, some studies suggest that the following factors are related to night vision complaints:

High degrees of myopia (>5 diopters)
Age greater than 50 years old
Small diameter treatments (<=6.0 mm)
Residual astigmatism after treatment
Residual myopia or hyperopia (>0.50 D) after treatment.

The above list is derived from papers published before the modern wavefront era. In 2005, Captain Steve Schallhorn, M.D., of the U.S. Navy Refractive Surgery program presented data at the Annual Symposium of American Society of Cataract and Refractive Surgery (ASCRS) from a collaborative armed forces study that showed that wavefront-guided treatments produce superior night vision and better contrast sensitivity than conventional treatments. Other studies have shown that some wavefront patients obtain better night vision than they had with glasses or contacts. Still, wavefront treatments don't entirely eliminate the possibility of glare and halos.

Haze is a potential side effect unique to the flapless procedures PRK, LASEK and Epi-LASIK. Only in very rare circumstances does it occur with LASIK or IntraLASIK. Haze appears as lattice-like areas of corneal opacification in the area of the laser treatment. Mild haze is common and often of no visual significance, while moderate to severe haze is less common, but more likely to cause blurred vision.

When laser vision correction with PRK was first introduced in the mid 1990's, haze was common and often problematic. The lack of haze with LASIK was the primary medical reason that LASIK rapidly became the procedure of choice for most surgeons. The other reason was the “wow factor" patients described from its rapid, overnight recovery.

In the past few years, many surgeons have developed a renewed interest in flapless surgery. Part of the reason lies in the desire to avoid flap complications altogether and another part lies in the dramatic decrease in haze possible with modern lasers and surgical techniques. Modern lasers reshape the cornea more smoothly, which is thought to decrease the stimulus for haze, and intraoperative treatment of the cornea with a medication known as Mitomycin-C further reduces the likelihood of haze to a very low level.

Over or undercorrection: All FDA-approved lasers used in laser vision correction are incredibly accurate and precise. However, variability in biological tissue, healing and other factors can sometimes lead to undercorrection or overcorrection. For example, a farsighted patient with +3.00 diopters of farsightedness may achieve +2.00 diopters of effect from the laser treatment (undercorrection) or +4.00 diopters (overcorrection). Patients who are within ±0.50 diopters of the intended target are almost always happy and see well. Those who are ±0.75 diopters are usually still pleased, but patients ±1.00 diopters or more from the intended target often request a second laser treatment (a "retreatment" or "enhancement") to further clear the vision.

Pain and light sensitivity: Mild to moderate pain and light sensitivity are common during the first three to five days after the flapless procedures PRK, LASEK and Epi-LASIK. Though modern surgical techniques such as cooling the cornea after laser treatment and prescribing dilute anesthetic drops have made flapless surgery more comfortable than in years past, flap procedures such as LASIK and IntraLASIK are still the most comfortable.

With LASIK, pain and light sensitivity are typically brief and mild. The same is true for most IntraLASIK patients. However, a small percentage of IntraLASIK patients develop a syndrome called Transient Light Sensitivity (TLS). TLS typically begins two to eight weeks after uneventful surgery and manifests as extreme light sensitivity, yet the vision remains clear. TLS is treated with anti-inflammatory eye drops.

Recent upgrades to the Intralase laser are thought to reduce the likelihood of TLS. Instead of large, high-energy laser spots spaced widely apart, the current protocol calls for small, low-energy spots spaced more closely together.

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