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Astigmatic keratotomy, also known as arcuate keratotomy or AK, is a procedure that corrects astigmatism. Astigmatism occurs when your cornea's curvature is not spherical like a basketball, but oval like an egg. As a result, one meridian (curvature) of your cornea is flatter, while the other is steeper.
AK is a type of corneal relaxing incision (CRI) surgery. These surgeries correct astigmatism by flattening the steeper areas of your cornea.
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Astigmatic keratotomy may be ideal for people who have:
Most times, AK is performed on people who have residual astigmatism after previous eye surgery, such as:
AK is an outpatient procedure, meaning you can go home shortly after the surgery. The surgery itself only takes about 5 minutes per eye.
Before the procedure, the surgeon obtains a corneal topography. This serves as a map to guide the surgeon on where to make the incisions. Another measurement called corneal pachymetry tells the surgeon how thick your corneal tissue is, which helps determine how deep the incisions can go.
To numb your eyes, the surgeon instills anesthetic eye drops. Then, they place a lid speculum to hold your eye open during surgery. The surgeon places temporary markings on your cornea that indicate where they will make the incisions.
Traditionally, the surgeon uses a diamond surgical blade. Many surgeons are now using a laser to create the incision, which may result in more precise outcomes.
The surgeon typically makes one or two incisions parallel to the edge of your cornea. These incisions are located along the steepest meridian of your cornea.
Generally, the deeper or longer the incision, the more astigmatism is corrected. Shallower or shorter incisions result in less correction. Reducing the distance between the two incisions also increases the amount of astigmatism correction.
AK tends to be more effective in older patients. The surgeon can make shorter incisions in these cases. For younger patients, the surgeon may create longer incisions.
The surgeon prescribes antibiotic eye drops (and possibly steroid eye drops) to use for several days after surgery. You may need to use eye shields to protect your eyes. If you experience discomfort, you can take some over-the-counter pain relievers. Other post-surgical symptoms include:
These symptoms are normal and usually go away within a day or two. Full healing time is about 2 to 3 months, although your vision should improve within a day or so. Most people can return to work and resume normal activities the next day.
Another type of corneal relaxing incision surgery is limbal relaxing incisions (LRI). The techniques involved are similar to those of AK. Currently, LRI surgeries are performed more often than AK. Here are some pros and cons that highlight the differences between these procedures.
Astigmatic keratotomy is considered safe and effective. However, a small percentage of people experience side effects that may be temporary or permanent. Some side effects and complications include:
In addition to astigmatic keratotomy and limbal relaxing incisions, there are other procedures that correct astigmatism, including:
In modern eye surgery, many surgeons favor laser refractive surgery (LASIK or PRK) over corneal relaxing incision surgeries. However, combining laser eye surgery with AK may benefit patients with high astigmatism. The laser can correct a majority of the prescription, while AK treats any residual astigmatism. This combination may lead to a better quality of vision and less glare at nighttime.
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Zheng, Lin-Yan, et al. “Comparison between Toric and Spherical Phakic Intraocular Lenses Combined with Astigmatic Keratotomy for High Myopic Astigmatism.” Eye and Vision, vol. 4, no. 20, 18 Aug. 2017, doi:10.1186/s40662-017-0085-7.