Astigmatism is a common refractive error where the cornea or the lens has an irregular, non-spherical curvature, shaped more like a football than a baseball. This oval shape causes light entering the eye to focus at multiple points instead of a single point on the retina, resulting in blurred or distorted vision at any distance. Modern laser eye surgery procedures, including Laser-Assisted In Situ Keratomileusis (LASIK) and Photorefractive Keratectomy (PRK), are highly effective at correcting this irregularity. These procedures offer a long-term solution to reduce or eliminate the need for corrective lenses for most patients with astigmatism.
Correcting the Corneal Shape
Treating astigmatism requires precisely changing the cornea’s irregular surface to a more uniform, spherical shape. The excimer laser uses ultraviolet light to remove microscopic amounts of tissue to accomplish this reshaping. This procedure is more complex than correcting simple nearsightedness, as it must address the error along a specific axis rather than uniformly across the entire cornea.
Before treatment, advanced diagnostic tools, such as corneal topography or wavefront analysis, map the eye’s surface. These systems capture data points to create a detailed, three-dimensional profile of the corneal curvature. This mapping allows the surgeon to program the excimer laser with a customized ablation profile.
The laser vaporizes tissue in a non-spherical pattern, removing more tissue along the steeper meridian and less along the flatter meridian. This differential removal smooths the surface, causing light to be refracted evenly and focused correctly onto the retina.
Screening Criteria for Astigmatism Patients
A thorough screening is necessary to ensure a safe and predictable outcome for astigmatism patients. Primary considerations include the magnitude of the error, as LASIK and PRK can correct astigmatism up to approximately 6.00 diopters (D).
Corneal thickness is another significant factor because correcting astigmatism often requires removing more tissue than treating simple nearsightedness. If the cornea is naturally thin, removing too much tissue may compromise the eye’s structural integrity. Surgeons measure the cornea to ensure a safe residual stromal bed thickness remains after the procedure.
The patient’s prescription stability is also reviewed, requiring no significant change for at least 12 months. Pre-existing eye conditions must be ruled out, particularly keratoconus, a progressive disorder that causes the cornea to thin and bulge outward. Performing laser surgery on an eye with keratoconus could worsen the condition and lead to poor visual results.
Recovery and Visual Outcomes
Following laser correction, patients should expect a period of fluctuating vision as the eye heals and adapts. For LASIK, visual improvement is rapid, with many patients noticing clearer vision within 24 hours and returning to most activities in one to two days. PRK requires a longer healing period since it does not involve creating a corneal flap, with functional vision returning over several days to a week.
Full visual stabilization takes between three to six months. In the initial weeks, some patients may experience temporary visual disturbances such as glare, halos, or dry eye symptoms. These effects are common and diminish as the cornea fully heals and the tear film normalizes.
The success rate for achieving excellent visual acuity is very high, with many patients achieving 20/20 vision or better. A small percentage of individuals, especially those with a high degree of astigmatism, may experience residual astigmatism or undercorrection. This may necessitate an enhancement procedure, or “touch-up,” performed once the vision has remained stable for several months.