Laser-assisted in situ keratomileusis (LASIK), now the most commonly performed refractive surgery, is an effective treatment for near-sightedness (myopia) with and without astigmatism, as well as far-sightedness (hyperopia) with and without astigmatism. LASIK is an outpatient surgery performed with topical anesthesia. A microkeratome, which works like a carpenter's plane, is used to raise a corneal flap. This flap usually averages 160 microns thick (about the thickness of a thin piece of paper) and is folded back to expose the underlying cornea.
The excimer laser is used to reshape a precise amount of corneal stroma and the flap is then put back in place (see figure below). No sutures are needed. Flap stability and adherence to the corneal stroma are checked after surgery and patients are usually sent home on topical steroid, topical antibiotic, and topical nonsteroidal drops. The patient also is instructed to use an eye shield overnight with follow-up typically scheduled on postoperative day one and then at one week. The patient is usually seen again at one, three, and six months.
LASIK has significant attractions for the patient. It causes little pain, provides quick recovery of vision, and has the potential for treating higher levels of myopia. LASIK enhancements are more easily performed, at least within the first 6 to 12 months, by lifting the original flap and retreating the stromal bed to correct any residual refractive error. LASIK produces less stromal haze than PRK (photorefractive keratectomy) and does not require continuous steroid therapy.
PREOPERATIVE EVALUATION — The initial clinical workup includes a complete medical and surgical history. The ophthalmologist reviews the general medical history particularly looking for a diagnosis of diabetes mellitus, collagen vascular diseases, and immunocompromise of any etiology. The surgeon must also have a detailed ocular history before performing refractive surgery, paying special attention to previous ocular surgery as well as conditions such as glaucoma, strabismus, amblyopia, and dry eye syndrome.
Contact lenses — Prior to refractive surgery, patients want to remove their contact lenses, which can temporarily change the shape of the cornea. Soft contact lenses should be discontinued at least two weeks prior to an examination and following treatment. Rigid gas permeable (RGP) lenses should be discontinued at least three weeks prior to an examination and demonstrate a stable keratometry and refraction.
Eye examination — The initial patient visit includes a complete eye exam which may include testing of uncorrected and corrected visual acuity, refraction, slit lamp examination, pupil size, dry eye evaluation, corneal thickness and evaluation, intraocular pressure, and glaucoma evaluation and management. The patient’s eye must be healthy and the refractive error must be stable over ~one year of time.
The most common complaints following refractive surgery are dry eyes and difficulty with night driving and glare. Surgical complications include over- or under correction and infectious or inflammatory keratitis. Ten year outcome studies for PRK and LASIK demonstrate stability of visual correction, following the first two years, and high patient satisfaction (95.4% of 2,200 patients in 19 studies).
[Bower KS. (2010, September 17). Laser Refractive Surgery. Uptodate.com. Accessed February 25, 2011.]
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