context: Vision correction surgery, also called refractive and laser eye surgery, refers to any surgical procedure used to fix vision problems. Recent years have seen huge advances in this field. Refractive and laser eye surgery allow many patients to see better than any other time in their lives. Most types of vision correction surgery reshape your cornea, the clear front part of your eye. That lets light travel through it and focus properly on the back of your eye, or retina. Other procedures replace your eye's natural lens. LASIK, or laser in-situ keratomileusis, works for people who are nearsighted, farsighted, or have astigmatism. The doctor makes a flap in the outer layer of the cornea to get to the tissue underneath. He then uses a laser to reshape the tissue underneath your cornea so it can focus light properly. The flap is what makes LASIK different from other procedures. The doctor may also use a type of computer imaging called wavefront technology to create a detailed image of your cornea that she can use as a guide. PRK, or photorefractive keratectomy, is used to correct mild to moderate nearsightedness, farsightedness, or astigmatism. Like LASIK, a surgeon uses a laser to reshape your cornea. But it only affects the cornea's surface, not the tissue underneath. Your doctor may also use computer imaging of the cornea. RLE stands for refractive lens exchange. Other names include PRELEX, clear lens exchange ( CLE), clear lens extraction ( CLE), and refractive lens replacement ( RLR). It's the same as cataract surgery. The doctor makes a small cut at the edge of your cornea. She removes your natural lens and replaces it with a plastic lens implant. The procedure can correct extreme farsightedness or nearsightedness. It works well for people with thin corneas, dry eyes, or other minor cornea problems. A LASIK or LASIK-related procedure can be combined with RLE to correct astigmatism. PRELEX, short for presbyopic lens exchange, is a procedure used for presbyopia, or loss of flexibility in your eye. The doctor removes your lens and replaces it with a multifocal lens. Intacs are also known as intracorneal ring segments, or ICR. The doctor makes a small incision in your cornea and places two crescent-shaped plastic rings at the outer edge. The rings flatten your cornea and change the way light rays focus on your retina. ICR was used to treat nearsightedness, but that has been replaced by laser-based procedures. Now it's used to fix keratoconus, an irregular-shaped cornea that causes your cornea to thin and results in vision loss. Phakic intraocular lens implants are designed for people who are too nearsighted for LASIK and PRK. The doctor makes a small incision at the edge of your cornea and either attaches the implant lens to your iris or inserts it behind your pupil. Unlike RLE, your natural lens stays in place. Visian ICL is the main type of phakic lens implant used. LRI is short for astigmatic keratotomy. It isn't laser eye surgery, but a surgical procedure used to correct astigmatism. When you have astigmatism, your eye is shaped like a football instead of being round. The doctor makes one or two incisions at the steepest part of your cornea. This helps it relax and makes it more rounded. This procedure can be done alone, or in combination with other laser eye surgeries like PRK, LASIK, or RK. Their good results are well-documented, but like any surgery, there can be side effects. It's important to keep them in mind. Infection and delayed healing. A tiny number of people get an infection after PRK or LASIK. It generally means added discomfort and a longer healing process. Undercorrection or overcorrection. You won't know how well the surgery worked until your eye has healed properly. You may still need glasses or contacts. If your vision isn't great, a second laser surgery, called laser enhancement, can help. Worse vision. It's rare, but some people see worse than before the surgery. Irregular tissue removal or excess corneal haze are the usual culprits. Excess corneal haze. This can be a part of the natural healing process after PRK. It usually has no effect on your vision after and can only be seen through an eye exam. Sometimes it can affect your vision. You may need a second procedure.. Also, a medication called mitomycin C ( MMC) during PRK surgery can prevent it. Regression. Sometimes the effects of surgery go away over a period of months from atypical healing. You may need a second surgery to improve your vision. Halo effect. This happens in dim light and can make it hard to drive or see in dark places. As your pupil opens, the untreated area outside your cornea produces a second image. It can happen after LASIK or PRK. Your doctor can use laser optical zones or wavefront technology, which creates a 3- D version of your eye so your surgery is more precise, to make it less likely. Higher degrees of nearsightedness with LASIK and PRK increase the halo risk, while Visian ICL for higher nearsightedness has less halo risk. Flap damage or loss. LASIK leaves a hinged flap on the center of your cornea. It may need to be repositioned during the first few days after surgery or after a severe direct injury to your eye.