What is an Astigmatic Keratotomy or Limbal Relaxing Incision?
Astigmatic keratotomy (AK) or limbal relaxing incision (LRI) is a partial corneal thickness incision made in the peripheral cornea near the sclera (white portion of the eye) to treat corneal astigmatism.
What is Corneal Astigmatism?
The front surface of the clear portion of the eye (cornea) has an abnormal shape. The cornea is shaped more like a football cut length wise versus a basketball cut in half. The corneal astigmatism causes light rays coming into the eye to be focused into a linear pattern instead of a point. Patients complain of ghost images, a streak around lights, or double vision.
Types of Astigmatism
The axis or direction of the astigmatism is located 90 degrees from each other and the surface of the cornea is smooth. Most astigmatism is this type of astigmatism.
The axis of the astigmatism is not 90 degrees from each other and/or the surface of the cornea is not smooth. Irregular astigmatism cannot be corrected well with glasses as the glasses cannot be made to match the irregular pattern.
Diagnosis of Astigmatism
The diagnosis of astigmatism can be made with a routine eye exam.
Other Tests Used with Evaluation of the Eye for AK or LRI Incisions
Standard instrument used to measure the curvature of the cornea.
Corneal topography is a computerized instrument that is used to measure the surface of the cornea and produces a topographical map of the shape of the cornea.
An instrument is used to measure the thickness of the cornea in the area of where the surgery is going to be performed.
Astigmatic Keratotomy or Limbal Relaxing Incision Surgery Procedure
Prior to the surgery, the patient’s cornea is marked with a surgery marking pen in order to place the incision in the right axis of the astigmatism.
The eye is anesthetized with a topical anesthetic.
The Surgical Procedure
The patient is placed on an operating and the eye is prepped and draped for an ocular procedure. A diamond knife is used to make the incision on the axis of the steeper portion of the cornea. The size and number of incisions is based on the amount of the astigmatism present. The diamond typically cuts at a depth of 600 microns to provide the desired result. The procedure takes only a minute or so to complete.
Complications of AK or LRI Procedures
Over or under correction of the astigmatism
Pain and/or foreign body sensation
Most patients do very well with the correction of their astigmatism with improved vision without glasses. The procedure has few complications and excellent results.