LASIK (Laser-Assisted In Situ Keratomileusis) is a procedure designed to correct refractive errors by permanently reshaping the eye’s clear front surface. However, LASIK is not an option for individuals with keratoconus. Keratoconus is a progressive, structural disorder of the cornea that makes it an unsuitable candidate for this type of surgery. Attempting to perform this refractive procedure on an already compromised cornea carries a significant risk of worsening the underlying disease. The medical community considers keratoconus a strong contraindication for LASIK because the structural changes induced by the laser can severely destabilize the eye.
Understanding Keratoconus
Keratoconus is a non-inflammatory, progressive eye disease that affects the cornea, the clear, dome-shaped outer layer of the eye. In a healthy eye, the cornea maintains a relatively spherical shape, but in keratoconus, the tissue thins and begins to bulge outward into a cone-like protrusion. This change in shape significantly alters how light enters the eye, leading to a distortion of vision that cannot be fully corrected with standard eyeglasses.
The visual symptoms of this condition typically include progressively worsening nearsightedness and irregular astigmatism, resulting in blurred or distorted images. Patients often experience increased sensitivity to light, known as photophobia, and glare, particularly when driving at night. Keratoconus usually begins in the late teens or early twenties and may progress for a decade or more before slowing down.
Diagnosis relies on sophisticated imaging technology to map the cornea’s shape and measure its thickness. Corneal topography is a non-invasive test that creates a detailed, color-coded map of the corneal surface curvature, which reveals the characteristic inferior steepening and asymmetric bowing. Pachymetry, another diagnostic component, precisely measures the thickness of the cornea across its surface.
A thinner-than-average cornea and a displaced thinnest point are strong indicators of keratoconus. Identifying the disease early is important for monitoring and treatment, as the structural changes disqualify a patient from procedures like LASIK. Advanced diagnostic tools can even detect subtle forms of the condition, sometimes referred to as forme fruste keratoconus.
Why LASIK is Not a Solution
The fundamental conflict between LASIK and keratoconus lies in the mechanical nature of the surgery and the underlying pathology of the condition. LASIK corrects vision by using an excimer laser to remove microscopic amounts of tissue from the corneal stroma. This ablation permanently reshapes the cornea to adjust its focusing power.
The procedure requires the creation of a corneal flap, which is lifted before the laser treatment and then repositioned. Both the flap creation and the subsequent tissue removal reduce the cornea’s overall structural strength. While acceptable for a healthy eye, this reduction is dangerous for a cornea already weakened by keratoconus.
Keratoconus involves a structural defect where collagen fibers are weak, causing the tissue to thin and stretch. Since the cornea is already structurally compromised and prone to bulging, the additional thinning from LASIK dramatically increases the risk of iatrogenic corneal ectasia. This complication is an acceleration or worsening of the cone-like bulging.
The mechanical stress placed on the delicate cornea after LASIK can trigger or accelerate progressive deformation, leading to severe and unpredictable vision loss. Reputable eye surgeons strictly adhere to this contraindication to prevent irreversible damage to the patient’s vision.
Effective Treatment Pathways for Keratoconus
Since LASIK is contraindicated, the management of keratoconus focuses on two primary goals: stabilizing the cornea to halt disease progression and correcting vision. These strategies often work in combination to provide the best long-term outcome.
Corneal Collagen Cross-Linking (CXL) is the only procedure approved to stop the progression of keratoconus. This minimally invasive treatment strengthens existing collagen fibers within the corneal stroma. The procedure involves applying riboflavin eye drops to the corneal surface.
The riboflavin acts as a photosensitizer that, when exposed to ultraviolet A (UVA) light, causes new chemical bonds, or cross-links, to form between the collagen fibrils. This reaction stiffens the cornea, making it more resistant to the forces that cause progressive bulging. Halting the progression preserves a patient’s remaining vision and prevents the need for more invasive surgery later.
Contact Lenses
For vision correction, the primary non-surgical solution involves fitting specialized contact lenses designed to counteract the irregular corneal shape. Rigid Gas Permeable (RGP) lenses are smaller and rest directly on the cornea, creating a smooth, artificial refracting surface. They provide significantly sharper vision than eyeglasses for many patients.
Scleral contact lenses represent an evolution in vision correction. These lenses have a much larger diameter and vault completely over the irregular corneal surface, resting instead on the sclera (the white part of the eye). The space between the lens and the cornea is filled with a sterile saline solution, which neutralizes corneal irregularities and provides superior comfort and stable, clear vision.
Surgical Options
In cases where the condition is more advanced, surgical options may be considered. One option is the implantation of Intracorneal Ring Segments (Intacs). These small, arc-shaped plastic inserts are placed within the corneal periphery to flatten the central cone and improve the cornea’s overall shape. Intacs restore a more regular contour, often improving a patient’s ability to achieve functional vision with contact lenses or glasses.
A corneal transplant may be performed for severe cases, particularly when there is significant corneal scarring or when vision cannot be corrected by lenses. Full-thickness transplants, known as Penetrating Keratoplasty (PK), involve replacing the entire diseased cornea with a healthy donor cornea. A less invasive option, Deep Anterior Lamellar Keratoplasty (DALK), replaces only the front layers of the cornea, allowing the patient to retain the healthy innermost layer, which potentially reduces the risk of rejection and speeds up recovery.