LASIK is a highly effective and widely used method for correcting the refractive error known as astigmatism. Astigmatism is a common visual problem that arises when the eye’s front surface, or cornea, is irregularly shaped. By precisely reshaping the cornea, Laser-Assisted In Situ Keratomileusis (LASIK) allows light to focus clearly onto the retina, thus correcting the distorted vision caused by this condition. This procedure is routinely performed to correct astigmatism, often simultaneously with nearsightedness or farsightedness, providing a solution for many seeking freedom from corrective lenses.
Understanding Astigmatism
Astigmatism occurs because the cornea, normally spherical like a basketball, is instead shaped more like a football. This irregular curvature means the eye has two different curves, causing light entering the eye to focus unevenly. Instead of converging to a single point on the retina, the light rays spread out across multiple points. The result is vision that appears blurred or distorted at any distance. Astigmatism is measured in diopters, and almost everyone has some degree of it, though it may be too small to require correction.
The LASIK Mechanism for Correction
LASIK corrects astigmatism by directly targeting and reshaping the irregularly curved cornea to make it more spherical. The procedure utilizes an excimer laser, a highly precise tool that removes microscopic amounts of corneal tissue through a process called photoablation. This removal of tissue flattens the steeper curve and steepens the flatter curve, smoothing the surface into a more uniform shape.
The precision required for astigmatism correction is achieved using advanced diagnostic technology, such as wavefront aberrometry. This technology measures unique imperfections across the eye’s surface, creating a personalized three-dimensional map, often called an “optical fingerprint.” This data guides the excimer laser, ensuring the treatment is precisely tailored to the patient’s specific astigmatism and axis. This custom treatment corrects higher-order aberrations that can affect vision quality, especially in low light. The entire process involves creating a thin corneal flap, applying the laser to the underlying tissue, and then repositioning the flap.
Factors Determining Eligibility
While LASIK is an effective treatment, not everyone with astigmatism is a candidate. A primary consideration is the maximum degree of astigmatism that can be safely treated, typically ranging up to 5.00 to 6.00 diopters. Higher levels of astigmatism necessitate the removal of more corneal tissue. The cornea must have sufficient thickness to remain structurally stable after the procedure. A minimum residual stromal bed thickness of 250 to 270 microns is generally required to maintain the cornea’s integrity.
Patients with naturally thin corneas or very high prescriptions may not qualify for LASIK and may be better suited for alternative procedures, such as photorefractive keratectomy (PRK). A stable prescription is also required, meaning the patient’s vision should not have changed significantly for at least 12 months prior to the surgery. The eyes must also be healthy, free from conditions like uncontrolled diabetes, severe dry eye syndrome, or other underlying eye diseases that could interfere with healing. A thorough pre-operative screening ensures the patient’s eye health falls within the safe and treatable range.
What to Expect Post-Procedure
Patients often experience a rapid improvement in their vision within the first 24 hours following the LASIK procedure. The immediate recovery period may involve temporary side effects as the eye heals, which can include a gritty sensation, light sensitivity, and dry eyes. These symptoms are common but generally improve significantly within the first few weeks to months.
Long-term studies show that LASIK results are highly stable, with the correction remaining effective for many years. Most patients achieve excellent visual acuity, often attaining 20/20 or 20/40 vision or better. Follow-up appointments are necessary to monitor healing and confirm the stability of the correction. While the corneal reshaping is permanent, LASIK does not prevent the natural aging of the eye, which may eventually lead to the need for reading glasses (presbyopia) after age 40. Patients must follow all post-operative care instructions to ensure optimal results.