FACTORS THAT MAY PREVENT YOU FROM HAVING LASIK
The following conditions may make you a poor candidate, or at least a less-than-ideal candidate, for LASIK. Although the conditions listed are generally contraindications to LASIK, many are not absolute contraindications. If you have one of these conditions, consultation with an experienced LASIK surgeon will help you determine whether LASIK is still a possibility for you.
THIN CORNEA
LASIK will not weaken a normal cornea, but if your cornea is unusually thin, LASIK could weaken it, causing distortion in your vision. If you have a thin cornea, PRK may be a better option for you. PRK is covered in detail in chapter 6.
KERATOCONUS
This is an uncommon, hereditary condition that weakens the cornea. The weak cornea bulges outward gradually over time, just as a bicycle tire with a weak spot develops a bulge. Patients with this condition suffer from increasing nearsightedness, astigmatism, and poor vision. Keratoconus progresses gradually in younger people and then stabilizes around the age of forty.
Unfortunately, the LASIK flap can make this condition worse, so LASIK is not a good option for patients with keratoconus. Sometimes, patients with this condition can be treated with PRK instead. An essential part of your preoperative exam is examining you for keratoconus, using a specialized diagnostic map of the eye called corneal topography.
CATARACT
A cataract is a clouding of the lens within the eye that causes blurry vision. If you have a cataract, LASIK can accentuate the blurring of vision caused by the cataract. Patients with a cataract are usually good candidates for refractive lens exchange because refractive lens exchange corrects both the vision and the cataract. RLE is covered in detail in chapter 8.
BASEMENT MEMBRANE DYSTROPHY
This is a hereditary condition that causes the epithelium, the clear skin that covers the cornea, to slough off spontaneously, creating a corneal abrasion. It is a relatively common condition. People with basement membrane dystrophy can develop corneal abrasions after LASIK. These can cause discomfort and a slow recovery of vision after the procedure.
PRIOR EPISODES OF HERPES KERATITIS
The same herpes virus that causes cold sores on the lips can cause recurring infection in the eye, resulting in scarring and blurred vision. LASIK can cause a reactivation of the virus. LASIK can often be done safely by pretreatment with drugs that suppress the virus. Note: this herpes virus is different from the virus that causes genital herpes, which is a sexually transmitted disease.
SIGNIFICANT DRY EYE
LASIK makes the eyes somewhat drier, so patients who have very dry eyes to start with can be somewhat uncomfortable after LASIK. Mild dry eye can also make wearing contact lenses very uncomfortable. All in all, people with mild dry eye often do much better with LASIK than with contact lenses. The surgeon will evaluate your tear production and advise you if LASIK is a good alternative for you. LASIK and dry eye is discussed in more detail later in this chapter.
The Lasik Flap
