Keratoconus: Symptoms, Causes, Diagnosis, and Treatment

Keratoconus is a progressive eye disease that affects the cornea—the clear, dome-shaped surface that covers the front of the eye. In keratoconus, the cornea thins and gradually bulges outward into a cone-like shape, leading to blurred vision, increased sensitivity to light, and, in advanced cases, significant vision loss.

What is Keratoconus?

Keratoconus is a disorder characterized by a gradual thinning and outward bulging of the cornea. The cornea, normally shaped like a rounded dome, becomes cone-like over time. This change distorts vision and can significantly impact visual acuity—more so than common refractive errors like nearsightedness or astigmatism.

In most cases, the condition progresses slowly, typically beginning in adolescence or early adulthood. While keratoconus generally affects both eyes, the severity can differ between them.

• Corneal thinning: Weakens the cornea’s structure
• Cone-shaped bulge: Alters the way light enters the eye
• Irregular astigmatism: Distorts and blurs vision

How Does Keratoconus Affect the Eye?

The cornea is responsible for focusing light onto the retina, allowing for clear vision. In keratoconus, the structural integrity of the cornea is compromised, leading to a host of visual problems:

• Blurry vision not fully correctable by glasses
• Distorted or wavy vision
• Sensitivity to light or glare
• Frequent changes in eyeglass prescription
• Difficulty with night vision

As the disease advances, the cornea becomes increasingly thin and misshapen, sometimes developing scar tissue that further affects vision.

What Are the Symptoms of Keratoconus?

The initial symptoms of keratoconus are often subtle but tend to worsen over time. Early signs may be mistaken for other refractive errors, making early diagnosis difficult. Common symptoms include:

• Blurred or distorted vision that cannot be corrected fully with glasses
• Increased sensitivity to light and glare
• Nearsightedness (myopia) and astigmatism that progress over time
• Frequent changes to your vision prescription
• Eye strain or headaches due to visual discomfort
• Halos around lights, especially at night
• Poor night vision

Symptoms usually begin in the late teens to early 20s, though the condition can develop later or earlier in rare cases. Vision in both eyes may be affected, though often asymmetrically.

Who Gets Keratoconus?

Keratoconus can affect anyone, but certain groups carry a higher risk. Its exact cause is often unclear, but the disease may be influenced by both genetic and environmental factors. Risk factors include:

• Family history: A clear hereditary component—your risk increases if a parent or sibling has the disease
• Frequent or forceful eye rubbing: Especially in those with allergies or other conditions causing itchy eyes
• Chronic eye irritation: Conditions like allergic conjunctivitis
• Certain medical conditions: Higher rates in people with Down syndrome, Leber congenital amaurosis, or connective tissue disorders
• Ethnicity: Higher prevalence observed in select populations in some studies

While keratoconus can develop at any age, it is most commonly detected in adolescence and tends to progress until the 30s or 40s, when it may stabilize.

What Causes Keratoconus?

The underlying cause of keratoconus is not completely understood, but several factors are implicated in its development:

• Genetic predisposition: Many cases appear to run in families, suggesting a hereditary component
• Structural changes in corneal collagen: Weakening of collagen fibers makes the cornea less resistant to external forces
• Enzymatic imbalance: An excess of certain enzymes weakens and breaks down corneal tissue
• Oxidative stress: Increased susceptibility of corneal tissue to damage from metabolic by-products
• Dysregulated wound healing: The cornea may undergo abnormal repair processes, further degrading its structure

Eye rubbing, especially in those prone to allergies, may accelerate or complicate the disease. Other associated conditions include atopic diseases, Ehlers-Danlos syndrome, and osteogenesis imperfecta.

What Are the Stages of Keratoconus?

Keratoconus typically progresses through various stages, each with distinct features and implications for management:

Progression can be unpredictable; for some, it stabilizes early, while in others, it rapidly advances. Monitoring and early intervention are key to managing keratoconus effectively.

How is Keratoconus Diagnosed?

Diagnosis involves both a clinical eye examination and advanced imaging tests. Eye care professionals use the following methods to confirm and assess keratoconus:

• Slit-lamp examination: Detects thinning, conical bulging, and sometimes corneal scars
• Keratometry: Measures the curvature of the cornea and can show irregular steepening
• Corneal topography: Creates a detailed map of corneal shape, revealing distortions typical of keratoconus
• Pachymetry: Measures corneal thickness at different points
• Corneal tomography: Provides 3D views of the cornea’s structure and thickness

Early forms of keratoconus may be subtle, making specialized imaging important for detecting and assessing the degree of disease. Regular follow-up exams help track progression.

What Are the Possible Complications?

Though many patients manage well with conservative treatments, keratoconus can sometimes cause severe complications:

• Corneal scarring: Especially if the cornea is extremely thin or develops ruptures
• Vision loss: When the disease is advanced and not correctable with lenses or glasses
• Hydrops: A sudden buildup of fluid in the cornea, causing pain and rapid vision decline; usually resolves but sometimes leaves permanent scarring
• Poor contact lens tolerance: Due to irregular corneal surface

How is Keratoconus Treated?

Treatment for keratoconus varies based on the stage and severity of the disease. The primary goals are to improve vision and halt or slow disease progression. Common interventions include:

Non-Surgical Treatments

• Eyeglasses: Suitable in early stages to correct mild refractive errors
• Rigid Gas Permeable (RGP) Contact Lenses: Provide better correction for moderate keratoconus by masking corneal irregularities
• Hybrid and Scleral Lenses: Specialized lenses that vault over the irregular cornea and provide excellent comfort and vision

Collagen Cross-Linking (CXL)

This in-office procedure uses ultraviolet (UV) light and riboflavin (vitamin B2) drops to strengthen the collagen fibers in the cornea, stabilizing its structure and slowing or halting progression. CXL is most effective when performed early in the disease course. It does not restore lost vision but can prevent worsening.

Cornel Implants (Intacs)

Plastic semi-circular rings inserted into the cornea can flatten and reshape the cornea, sometimes improving vision and lens fit. Indicated for moderate disease when contact lenses are not tolerated.

Surgical Procedures

• Corneal Transplantation: In severe, advanced cases with significant scarring or corneal thinning, a corneal transplant (penetrating keratoplasty or deep anterior lamellar keratoplasty) may be required to restore vision

Living with Keratoconus

Most people with keratoconus are able to lead normal, active lives with the help of glasses, contact lenses, or surgical treatments.

• Regular follow-up visits with an eye care specialist are essential for monitoring progression and updating treatment.
• Minimize eye rubbing and manage allergies to reduce the risk of worsening corneal damage.
• Protect eyes from trauma and seek prompt care for sudden changes in vision or discomfort.

Ongoing advances in diagnosis and treatment continue to improve the outlook for individuals diagnosed with keratoconus.

Frequently Asked Questions (FAQs)

What is the main cause of keratoconus?

The precise cause of keratoconus remains unclear. Genetics, environmental factors, and biomechanical influences on the eye all contribute—collagen weakness and possibly increased enzymatic activity play a role.

Can keratoconus be cured?

There is no permanent cure for keratoconus. However, vision can be managed with glasses, specialized contact lenses, or surgical treatments. Corneal collagen cross-linking can slow or stop progression if caught early.

Does keratoconus always progress?

Most cases of keratoconus progress slowly, especially in younger individuals. The disease often stabilizes by age 40, though this varies widely. Regular monitoring is vital for timely intervention.

Can you drive with keratoconus?

Many people with early or well-managed keratoconus can drive safely using glasses or contact lenses. Advanced keratoconus may significantly impair vision, making driving unsafe until treated.

Who should be screened for keratoconus?

Individuals with a family history, progressive nearsightedness, frequent prescription changes, or chronic eye rubbing should have regular eye exams, as early detection allows for better management.

Key Takeaways

• Keratoconus is a progressive corneal disease that causes thinning and cone-like protrusion, severely impacting vision.
• Early diagnosis and treatment improve outcomes—look for frequent prescription changes, blurry vision, and light sensitivity.
• Treatment options range from glasses and specialized contact lenses to surgical procedures and corneal transplantation.
• Corneal collagen cross-linking can halt disease progression if administered early.
• Ongoing ophthalmologist care is crucial for lifelong vision health.