Laser-Assisted In Situ Keratomileusis (LASIK) is a popular procedure for correcting common vision problems like nearsightedness and astigmatism. However, for individuals with keratoconus, a progressive eye disorder, traditional LASIK surgery is not a suitable corrective option and is generally discouraged. The underlying pathology of keratoconus makes the procedure a risk to the patient’s vision. LASIK cannot correct the structural weakness associated with this corneal condition; in fact, it can significantly worsen it.
Understanding Keratoconus
Keratoconus is an eye disorder that affects the cornea, the clear, dome-shaped front surface of the eye. In this condition, the central or paracentral part of the cornea progressively thins and bulges outward. This bulging creates an irregular cone shape, which is where the condition gets its name.
The cornea is composed of collagen fibers, which provide the structural rigidity necessary to maintain its curvature. When the cornea thins and distorts, light is not focused correctly onto the retina, causing significant vision problems. Symptoms often begin in the late teens or early twenties.
The disorder is progressive, meaning the thinning and bulging can continue over time, often for a decade or more, leading to poorer vision. The rate of progression varies, but the change in corneal shape is detectable through specialized diagnostic tools like corneal topography. Understanding this structural fragility explains why certain procedures are inappropriate for management.
Why LASIK is Not an Option
LASIK is a refractive surgery that permanently reshapes the cornea using an excimer laser. The procedure involves creating a thin flap on the corneal surface. The laser then removes microscopic layers of tissue from the underlying corneal stroma, which flattens the cornea to correct refractive errors like myopia and astigmatism.
The mechanism of LASIK is incompatible with the structural pathology of keratoconus. Keratoconic corneas are already structurally compromised and thinner than healthy corneas. Performing LASIK requires removing additional tissue, which further reduces the overall thickness and biomechanical strength of the fragile cornea.
This reduction in structural support accelerates the bulging and distortion of the cornea. Internal eye pressure acts on the weakened corneal wall, leading to a rapid and severe progression of the cone shape. This complication is known as post-LASIK ectasia, which is an induced form of keratoconus resulting from the surgery.
Keratoconus is an absolute contraindication for traditional LASIK surgery. The procedure can lead to unpredictable and severe changes in corneal shape, resulting in significant loss of vision. Surgeons use detailed corneal mapping to screen all potential LASIK candidates for even mild signs of keratoconus to prevent this complication.
Effective Treatment Pathways
Since LASIK is not a viable treatment, management for keratoconus focuses on two primary goals: stabilizing the cornea to halt disease progression and correcting the resulting vision distortion. The primary stabilization treatment is Corneal Cross-Linking (CXL). CXL is a minimally invasive procedure that uses riboflavin eye drops and ultraviolet A (UVA) light.
The riboflavin acts as a photosensitizer. When activated by UVA light, it creates new molecular bonds, or “cross-links,” between the collagen fibers within the corneal stroma. This process increases the cornea’s rigidity and mechanical stability, strengthening the tissue to stop progressive thinning and bulging. CXL is the only treatment proven to slow or halt the progression of keratoconus, potentially preventing the need for a corneal transplant.
Once stabilized, vision correction is achieved using specialized contact lenses. Standard soft contact lenses are often ineffective due to the irregular corneal surface. Patients are frequently fitted with rigid gas permeable (RGP) or scleral contact lenses, which create a smooth, artificial refractive surface that significantly improves visual acuity.
Advanced Vision Correction
In advanced cases where the cornea has excessive scarring or thinning, other procedures may be necessary. These include the insertion of Intacs (small corneal ring segments) to flatten the cone, or a corneal transplant to restore functional vision.