LASIK Flap Complications
By Jenny Kimberley
LASIK complications are extremely rare, occurring in less than one percent of LASIK procedures and often not impairing vision. Of those that do cause vision problems, most can be corrected with further surgery, eye drops, or medication. Some of the reasons that LASIK complications have become so rare are:
- Better patient screening
- More alternative ways of doing laser vision correction
- Better patient education
- Use of Wavefront technology
If you are considering LASIK, your eye surgeon will discuss the possible complications before anything is done. It is important to know the risks as well as the benefits of any surgery. Part of the responsibility for avoiding complications lies with your surgeon of course, but part also lies with you as the patient. You will be given printed instructions for use during your recovery. Your best results will partly depend on your following those instructions to the letter. For more on this, please see LASIK Benefits and Risks.
Most LASIK complications involve the corneal flap that is made at the beginning of the procedure. It is folded back to allow vision correction to be done on a deeper corneal layer (the stroma). Then it is replaced, smoothed down, and allowed to heal by itself. The eyes therefore need some protection for a while to allow the cornea to recover safely.
Striae are wrinkles in the corneal flap. They are most common in correction of myopia, but can also occur in correction of hyperopia. Trauma or stress to the flap can create the wrinkles. Higher corrections and thinner flaps are more likely to develop striae, and conditions such as dry eye can also contribute.
Not all striae affect vision but when severe they can reduce vision and cause ghosting. They can be corrected by surgically smoothing or repositioning the flap. The risk of developing striae can be significantly reduced during recovery by keeping the eyes moist with drops, protecting the eyes from any impact, and avoiding rubbing and excessive blinking.
When the flap is torn, unevenly cut, or too thin, it can develop a hole. This can be caused by a worn or poorly fitted microkeratome blade. If a buttonhole flap occurs, the surgeon will stop the procedure immediately to avoid damage to the eye. The flap will be allowed to heal, usually for three to six months, before surgery is attempted again. By causing scarring, buttonhole flaps can impair vision. They are more common in patients with very steep corneas, which is why a too-steep cornea (severe myopia) is a disqualifying factor for LASIK.
A Free flap
Occasionally the flap’s hinge will be cut through and the flap will be entirely detached. In most cases the surgery can be continued safely and the flap properly replaced. Older forms of the surgery intentionally created a free flap. Vision problems rarely occur, but in some cases the flap may be damaged or lost. The corneal surface continually replaces itself with new cells, so the lost tissue will usually grow back during recovery.
Diffuse Lamellar Keratitis
Inflammation of the cornea, called Diffuse Lamellar Keratitis (DLK) or “Sands of Sahara”, is caused by a reaction to debris under the flap. Mild inflammation can be treated with anti-inflammatories or topical steroids. Additional surgery may be required, in which the flap is lifted and the infected area is irrigated to remove the offending debris and inflamed cells. DLK must be addressed and treated quickly. If allowed to progress to a severe level of inflammation, serious vision damage may occur.
One of the factors considered in LASIK candidacy is corneal thickness. If your corneas are thinner than average, LASIK may not be safe. When the LASIK microkeratome cuts the corneal flap, it may be too thick for a relatively thin cornea. Further, the LASIK laser will be removing tissue for vision correction. and a too-thin cornea may therefore be weakened.
The eyes are filled with fluid that exerts pressure against the eyeball periphery and the cornea is part of that periphery. If it is thin to start with, weakened by the flap cutting, and then thinned further by LASIK, it may become too weak to hold its shape against the eye’s internal pressure. It may begin to bulge and distort vision. This is called ectasia.
Corneal topography before surgery can determine if the cornea is too thin for a safe procedure. Ectasia cannot be corrected by additional LASIK procedures although it can sometimes be corrected with contact lenses. In extreme cases a corneal transplant is required.
For more on eye anatomy, please see How the Eyes Work.
Epithelial ingrowth is a type of scarring that occurs when the cells lining the surface of the eye migrate underneath the flap. Although this scarring can sometimes cause vision distortion, it usually does not. If vision is not impaired, no treatment is necessary. If treatment is required, the flap is lifted and the epithelial cells are scraped away. Typically, epithelial ingrowth does not appear until one to three months after surgery, but occasionally will occur within the first few days.
If you are considering LASIK surgery, please contact an experienced ophthalmologist today.