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PHOTOREFRACTIVE KERATECTOMY (PRK)

PRK is a method of vision correction which uses the excimer laser to remove corneal tissue directly from the surface, without the benefit of a protective corneal flap or cap. PRK can be used to treat nearsightedness, farsightedness, and astigmatism.

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In PRK, the excimer laser is directly applied to the surface of the cornea, without making a corneal flap. For someone who is nearsighted, more corneal tissue is removed from the center than from the sides (peripheral cornea). This flattens the cornea and corrects the nearsightedness.

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For someone who is farsighted, more corneal tissue is removed from the sides (peripheral cornea) than from the center. This is like removing a "doughnut" of corneal tissue, making the cornea steeper, and thus correcting the farsightedness.

The amount of prescription correction that can be safely treated with PRK is debatable. Most surgeons feel treating up to 6-8 diopters of nearsightedness is safe with PRK. There is an increased risk of developing corneal haze when treating large amounts of prescription with PRK. This corneal haze is almost like scar formation; usually it fades over time, but can cause loss of best-corrected vision.

The drawbacks of PRK as compared to LASIK are, in fact, healing issues. At the completion of PRK, a large part of the cornea is abraded. More healing is necessary. It may take several days to get back useful vision, and there can be some degree of discomfort until the surface heals, usually 1-3 days, but sometimes longer. A "bandage" soft contact lens is inserted into the operated eye to make it more comfortable; it is removed after the abrasion heals. Weak anesthetic eyedrops can sometimes be cautiously used to numb the eye until it heals. Because of the temporary visual handicap, only one eye at a time is treated, which may require use of a temporary contact lens in the unoperated second eye (so the patient can function with both eyes), until the patient feels comfortable enough to proceed with second eye treatment. Steroid eyedrops are usually used for a much longer time than with LASIK, up to 4 months.

Despite what sounds like a long list of disadvantages, PRK is sometimes an excellent option for those patients who are not candidates for LASIK. Because no corneal flap needs to be made, PRK is arguably safer than LASIK. Patients, appropriately chosen and treated, can have excellent visual outcomes with PRK.

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