Astigmatic Keratotomy (AK)

Astigmatic keratotomy, also known as arcuate keratotomy or AK, is a procedure that corrects astigmatism.

AK is a type of corneal relaxing incision (CRI) surgery. These surgeries correct astigmatism by flattening the steeper areas of your cornea.

In the past, this surgery was done with diamond blades. Now, it's usually performed with a laser, which may result in more precise outcomes.

Ideal Candidates for Astigmatic Keratotomy Surgery

Astigmatic keratotomy may be ideal for people who have:

• A desire to reduce their dependence on glasses or contact lenses
• Mild to moderate astigmatism
• Stable eyeglass prescription for at least 1 year
• Good general health; diabetes and connective tissue diseases may affect the healing process
• No eye problems that may affect recovery, such as severe dry eyes

Most times, AK is performed on people who have residual astigmatism after previous eye surgery, such as:

• Cataract surgery
• Corneal transplant (penetrating keratoplasty or partial-thickness corneal transplants)
• Radial keratotomy 

What To Expect Before, During & After Surgery

AK is an outpatient procedure, meaning you can go home shortly after the surgery. The eye surgery itself only takes about 5 minutes per eye.

Before surgery

Before the procedure, the surgeon obtains a corneal topography. This guides the surgeon on where to make the incisions.

Another measurement called corneal pachymetry tells the surgeon how thick your corneal tissue is. This helps determine how deep the incisions can go. 

During surgery

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 with a laser.

They typically make 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 people. The surgeon can make shorter incisions in these cases. For younger people, the surgeon may create longer incisions.

After surgery

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 certain over-the-counter (OTC) pain relievers.

Other post-surgical symptoms include:

• Tearing
• Mild swelling
• Light sensitivity
• Redness
• Scratchy eyes

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.

Pros and Cons of Astigmatic Keratotomy

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 more common than AK.

Here are some pros and cons that highlight the differences between these procedures:

Pros of AK

• Quick and safe procedure
• Shorter incision length
• Corrects higher amounts of astigmatism
• Less costly than laser refractive surgery, such as LASIK

Cons of AK

• Deeper incisions, which carry a higher risk of penetrating the cornea
• Incisions are placed further from the edge of your cornea, which may result in increased glare and other vision problems
• More discomfort 
• Longer visual recovery
• Higher risk of overcorrection

Side Effects of Astigmatic Keratotomy Surgery

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:

• Overcorrection or undercorrection
• Light sensitivity, glare, and halos, which can be permanent for some people
• Infection, although rare
• Weaker corneal structure, which makes your cornea more vulnerable to injury

Alternative Treatment Options

Glasses and contacts are the most common treatments for astigmatism.

In addition to astigmatic keratotomy and limbal relaxing incisions, there are other procedures that correct astigmatism, including:

LASIK (laser in-situ keratomileusis)

LASIK is a laser eye surgery that corrects refractive errors, including astigmatism, myopia, and hyperopia.

This procedure may be more suitable for those with a combination of refractive errors (not only astigmatism).

PRK (photorefractive keratectomy)

PRK is another type of laser refractive surgery that also corrects astigmatism, myopia, and hyperopia.

Some people receive PRK instead of LASIK because they have thinner corneas or high prescriptions.

Others elect PRK to avoid having a corneal flap, such as in LASIK. This may include athletes who participate in high-impact sports.

Refractive Lens Exchange (RLE)

RLE is a procedure that removes the natural lens in your eye and replaces it with an intraocular lens implant (IOL).

The surgeon places a toric IOL into your eye. This is a type of implant that corrects astigmatism.

This surgery may correct higher astigmatism levels than AK.

Cataract Surgery

Cataract surgery involves the same steps as an RLE, except that the natural lens has developed into a cataract at the time of surgery.

For this reason, older patients with cataracts may choose this surgery over other procedures to correct astigmatism.

Phakic Intraocular Lens Implant (IOL) surgery

IOL surgery differs from RLE in that your natural lens is not removed. The implant is placed in front of the iris (anterior chamber) or behind the iris (posterior chamber).

This procedure primarily treats high myopia. But it can also correct astigmatism using toric phakic IOLs. 

In modern eye surgery, many surgeons favor laser refractive surgery (LASIK or PRK) over CRI surgeries.

However, combining laser eye surgery with AK may benefit people with high astigmatism. The laser can correct a majority of the prescription, while AK treats any residual astigmatism.

This combination may lead to better vision quality and less nighttime glare. 

Summary

Astigmatic keratotomy is a safe and effective procedure for correcting astigmatism. It can be used alone or in combination with other procedures for better results.

The best procedure for you will depend on your unique needs and the severity of your astigmatism. Always consult your eye doctor to determine the best treatment option.