Keratoconus is a condition in which the cornea — the clear, dome-shaped front surface of the eye — gradually thins and begins to bulge outward into a cone-like shape. As the cornea changes shape, it distorts the way light enters the eye, causing progressive blurring, distortion, and sensitivity to light and glare. It typically begins in the teens or early twenties and can progress for a decade or two before stabilizing. Early diagnosis and appropriate management are key to preserving good functional vision throughout the patient’s life.
How Keratoconus Develops
The cornea’s shape and strength depend on a scaffolding of collagen fibers arranged in precise layers. In keratoconus, the structural bonds between these collagen fibers are weakened, allowing the cornea to gradually thin and deform under the normal pressure of the eye. The resulting irregular, cone-like shape prevents the cornea from focusing light cleanly onto the retina, producing a type of distortion that standard glasses can correct only partially — particularly as the condition advances.
The exact cause of keratoconus is not fully understood. Genetic factors play a significant role — about 10 percent of people with keratoconus have a first-degree relative with the condition. Chronic eye rubbing is strongly associated with keratoconus progression and is one of the few modifiable risk factors. People with atopic conditions (eczema, hay fever, asthma) and certain connective tissue disorders have higher rates of keratoconus.
Recognizing the Symptoms
Keratoconus often begins with subtle visual changes that mimic ordinary nearsightedness or astigmatism. Mild blurring of vision, frequent changes in glasses prescription, and difficulty achieving sharp vision even with correction can all be early signs. As it progresses, the distortion becomes more pronounced — straight lines may appear wavy or ghosted, and visual quality may vary significantly depending on lighting conditions. Sensitivity to bright lights and glare, particularly at night, becomes increasingly bothersome.
Because early keratoconus is frequently misdiagnosed as simple astigmatism, suspicion should be raised whenever a young patient’s astigmatism is progressing rapidly, is asymmetric between the two eyes, or does not correct to normal visual acuity with standard glasses.
Diagnosis
Corneal topography is the essential diagnostic tool for keratoconus. This painless, non-contact test maps the curvature of the entire corneal surface using reflected light patterns, producing a color-coded map that reveals the irregular, cone-like shape that characterizes keratoconus. Corneal tomography (Scheimpflug imaging) provides additional three-dimensional information about corneal thickness and back surface elevation. Pachymetry — measuring corneal thickness at multiple points — confirms the localized thinning that typifies the condition.
Treatment Options by Stage
In early and moderate keratoconus, rigid gas-permeable (RGP) contact lenses are often the primary visual correction. Unlike soft lenses, which conform to the irregular corneal shape, RGP lenses vault over the cornea and create a smooth, regular refracting surface with the tear fluid underneath. Scleral lenses — large-diameter rigid lenses that rest on the white of the eye and vault entirely over the cornea — provide excellent vision and comfort for many keratoconus patients, including those who cannot tolerate standard RGP lenses.
Corneal cross-linking (CXL) is the most important treatment advance for keratoconus in recent decades. It uses riboflavin (vitamin B2) eye drops and controlled ultraviolet A light to strengthen the bonds between collagen fibers in the cornea, halting or significantly slowing the progression of the disease. Cross-linking does not restore corneal shape that has already been lost, but it stabilizes the condition and protects against further deterioration. It is most effective when performed early, before significant corneal changes have occurred.
For patients with advanced keratoconus whose vision can no longer be adequately corrected with contact lenses, surgical options include intrastromal corneal ring segments (ICRS) — small curved implants inserted into the cornea to flatten and regularize its shape — and, in the most severe cases, corneal transplantation (penetrating or deep anterior lamellar keratoplasty).
Our team provides comprehensive corneal evaluations and contact lens fitting for complex corneas. Visit our eye care services page or find a specialist through our provider directory.