Table of Contents
Refractive Surgery Definition
Refractive Surgery – operations to correct REFRACTIVE ERRORS of vision such as MYOPIA (nearsightedness), HYPEROPIA (farsightedness), and ASTIGMATISM (irregularity of the CORNEA).Refractive surgery became an option for permanent refractive correction in the United States in the 1980s, following its introduction and rapid growth in popularity in Europe. Now, about 1.5 million Americans undergo refractive surgery operations each year.
Refractive Eye Surgery Techniques
There are numerous refractive surgery techniques in use today. They fall into the general categories of those that use lasers, those that use microkeratomes (specialized blades), and those that use implants to alter the eye’s natural structure. There are five commonly performed refractive correction operations:
- LASIK (laser-assisted in situ keratomileusis) has become the standard procedure for most refractive corrections. The EYE surgeon makes a small flap to expose the inner portion of the cornea, uses an excimer (cool) laser to remove microscopically thin layers of corneal tissue, and replaces the corneal flap. Because the surface of the cornea, which contains NERVE endings, remains intact, there is almost no postoperative discomfort and results are immediately apparent. LASIK is most effective for hyperopia, astigmatism, and moderate myopia.
- Photorefractive keratectomy (PRK) was the original refractive LASER SURGERY. The eye surgeon uses an excimer laser to reshape the surface of the cornea. Results are not apparent until the cornea heals, which takes several weeks. There is some discomfort during the HEALING phase. PRK is particularly effective for people who have large pupils or thin corneas, because it does not create a corneal flap, which reduces the likelihood of postoperative glare and halos at night.
- Automated lamellar keratoplasty (ALK) is similar in concept to LASIK, though the surgeon uses a microkeratome, a specialized surgical blade. The eye surgeon makes a flap in the cornea and removes minute segments of corneal tissue, then replaces the flap. As with LASIK, there is little discomfort during healing and results are apparent immediately. ALK is particularly successful for severe myopia.
- LENS replacement uses techniques perfected through 60 years of CATARACT EXTRACTION AND LENS REPLACEMENT surgery. The eye surgeon removes the natural lens and replaces it with one curved to accommodate for severe hyperopia or myopia. Multifocal lens implants allow the eye to adjust between close and distant vision.
- Phakic intraocular contact lens implantation places a permanent contact lens in front of or behind the natural lens to supplement its focusing ability. This approach preserves the focusing ability of the natural lens.
The eye surgeon may choose other methods, depending on an individual’s refractive situation, age, and general health status. Not everyone with refractive errors is a good candidate for refractive surgery. It is important to consult with a qualified and experienced eye surgeon and to understand the potential risks and benefits of the different operations. Refractive surgery permanently alters the eye’s structure, although subsequent operations can often refine the effects when they are not as expected. Severe refractive errors may require multiple procedures.
Refractive Eye Surgery – Risks and Complications
As with any surgery, a potential complication of refractive surgery is postoperative INFECTION that can range from mild discomfort to significant damage to the eye with resulting VISION IMPAIRMENT. Prompt treatment prevents further complications. Most eye surgeons have stringent follow-up procedures intended to detect operative complications before they cause eye problems; it is important to maintain the recommended followup procedures. Other common complications include dry eyes and seeing halos around lights at night. Procedures involving lens replacement carry the additional risks of excessive bleeding and RETINAL DETACHMENT, which can compromise vision. Complications particular to LASIK include irregularity in the corneal surface after the corneal flap heals and overgrowth of corneal tissue that requires subsequent surgery to remove.
Occasionally the outcome is not as desired or expected, perhaps as a consequence of complications during the operation or during the healing process. It is important for the eye surgeon to appropriately match the person with the procedure, which takes into consideration the nature and severity of the refractive error, the person’s age and general health status, and the person’s expectations. Despite the precision of computerguided procedures, there remains an element of unpredictability that influences outcome. Some people may find their vision undercorrected and others overcorrected as a consequence of individual variation in eye structure, refractive error, and healing process.
Though the changes of refractive surgery are permanent, the effects on vision are not. Everyone eventually acquires PRESBYOPIA, a decrease in the ability to focus on near objects that is a function of change that occurs with aging. People who have had refractive surgery to correct astigmatism, hyperopia, or myopia will still need corrective measures for close vision as presbyopia develops. Nonsurgical solutions for presbyopia include contact lenses or reading glasses. Surgical solutions for presbyopia currently employ an approach called monovision, in which the eye surgeon undercorrects the vision in one eye for near focus. The refractive correction for the other eye is full, allowing for distant focus. The BRAIN does the work of switching between the eyes according to the vision needs.
Outlook and Lifestyle Modifications
Refractive surgery dramatically improves visual acuity for nearly everyone who has a successful surgical experience-that is, was properly matched to the correct procedure, had the operation performed by a competent and experienced eye surgeon, and had an uncomplicated course of recovery. Some people are able to completely eliminate the need for corrective lenses. Many people do still require corrective lenses, though at much improved refractive correction and perhaps only for specific applications such as near or midrange vision.
Doctors do not know what, if any, long-term consequences may result from refractive surgery, as most of the laser techniques predominantly in use today have been available only since the 1990s. Routine eye care and ophthalmic examinations are especially important for people who have had surgery on their eyes, to detect complications from the surgery as well as eye conditions such as GLAUCOMA, AGE-RELATED MACULAR DEGENERATION (ARMD), and CATARACT.