Keratoconus is a progressive eye disorder where the normally round dome-shaped cornea progressively thins and begins to bulge into a cone-like shape. This cone shape deflects light as it enters the eye on its way to the light-sensitive retina, causing distorted vision. Keratoconus typically begins during a person’s teens or early twenties and can affect one or both eyes.
Causes
The exact cause of keratoconus is not known, but several factors are believed to contribute to its development:
- Genetic Factors: A genetic predisposition may be involved, as the condition is more common in people who have a family history of keratoconus.
- Oxidative Stress: Some researchers believe that an imbalance between the production of free radicals and the body’s ability to detoxify their harmful effects might contribute to the thinning of the cornea.
- Enzymatic Imbalance: An imbalance in the enzymatic processes within the cornea can cause it to weaken due to inadequate amounts of protective antioxidants.
- Chronic Eye Rubbing: Frequent eye rubbing can increase the progression of keratoconus, so individuals who rub their eyes often (due to allergies or irritation) may be at higher risk.
- Connective Tissue Disorders: People with certain connective tissue disorders, such as Ehlers-Danlos syndrome or Marfan syndrome, may be more prone to developing keratoconus.
Symptoms
Symptoms of keratoconus often develop gradually and can differ from one person to another. Common symptoms include:
- Blurred Vision: Progressive and irregular astigmatism and nearsightedness lead to blurred vision, which is not always correctable with glasses.
- Distorted Vision: As the cornea changes shape, vision becomes increasingly distorted, making daily tasks difficult.
- Increased Light Sensitivity: Many people with keratoconus experience significant sensitivity to bright light and glare, which can cause discomfort and eye strain.
- Ghost Images: The irregular shape of the cornea can cause multiple images to appear, a symptom known as polyopia.
- Sudden Change in Vision: Rapid changes in vision can occur if the cornea swells and suddenly worsens.
- Difficulty with Night Vision: The change in the shape of the cornea can lead to halos around lights and blurred night vision.
As keratoconus progresses, these symptoms typically worsen, potentially leading to a significant impact on vision and quality of life. Regular eye exams are crucial for those with keratoconus, as early detection and treatment can help manage symptoms and slow progression of the condition.
Diagnostics
Diagnosing keratoconus typically involves a comprehensive eye examination with specific tests to assess the shape and function of the cornea:
- Eye Refraction: This test measures the eyes’ ability to focus light rays exactly on the retina at distance and close-up. Abnormal results may suggest keratoconus.
- Slit-lamp Examination: The optometrist or ophthalmologist uses a slit lamp to examine the cornea and other eye structures. This device allows the doctor to view the eye at high magnification to check for structural abnormalities.
- Keratometry: This test measures the curvature of the cornea’s surface. In keratoconus, the cornea becomes increasingly irregular and cone-shaped.
- Corneal Topography: Providing detailed information about the shape and curvature of the cornea, this mapping is crucial for diagnosing keratoconus and monitoring its progression.
- Pachymetry: Measures the thickness of the cornea. Thinning of the cornea is a hallmark of keratoconus.
Treatment
Treatment for keratoconus varies depending on the severity of the condition and how quickly it is progressing. The primary goal is to correct vision and to prevent further deterioration of the cornea:
- Eyeglasses or Soft Contact Lenses: In early stages, changes in vision caused by keratoconus can often be corrected with eyeglasses or soft contact lenses.
- Hard Contact Lenses: As the condition progresses, soft lenses may no longer provide adequate vision correction due to the irregular shape of the cornea. Rigid gas-permeable (RGP) contact lenses may be recommended.
- Piggyback Lenses: For those who cannot tolerate RGP lenses, «piggybacking» a soft contact lens underneath an RGP lens may improve comfort.
- Hybrid Lenses: These lenses have a rigid center with a soft outer ring, which can provide the clarity of RGP lenses with the comfort of soft lenses.
- Scleral and Semi-scleral Lenses: Larger in diameter, these lenses rest on the sclera rather than the cornea, providing comfort and clear vision.
- Corneal Cross-linking (CXL): A relatively new treatment that can stop the progression of keratoconus. CXL involves using ultraviolet light and a photosensitizer (vitamin B2) to strengthen chemical bonds in the cornea.
- Intacs Inserts: These are tiny, arc-shaped corneal inserts that are surgically placed in the periphery of the cornea to flatten the corneal surface and improve vision.
- Topography-guided Conductive Keratoplasty: Using radio frequency energy to reshape the cornea can be effective for some patients.
- Corneal Transplant: In severe cases, when vision cannot be corrected with other therapies and the cornea becomes dangerously thin or scarred, a corneal transplant may be necessary.
The choice of treatment is determined based on how much the keratoconus affects your daily life and whether the condition is stable or progressing. Regular follow-up appointments with an eye care specialist are crucial to monitor the condition and adjust treatment as necessary. Advances in treatment strategies continue to improve the outlook for people with keratoconus, allowing many to maintain active and productive lives.
Prevention
Preventing keratoconus is challenging due to its unclear causes and potential genetic links. However, there are measures that may help manage the condition or prevent it from worsening:
- Avoid Eye Rubbing: Chronic eye rubbing can contribute to the progression of keratoconus, so it’s important to avoid this habit. If eye itching is a problem due to allergies, consider seeking treatment for the allergies.
- Protect Your Eyes: Wearing protective eyewear during sports or activities that could lead to eye injuries can help maintain corneal integrity.
- Regular Eye Exams: Frequent check-ups can help detect early signs of keratoconus and other eye conditions, allowing for timely intervention.
- Manage Allergies and Asthma: Proper treatment and management of these conditions can reduce eye rubbing, thus potentially slowing the progression of keratoconus.
Complications
If left untreated or if treatment is inadequate, keratoconus can lead to several complications:
- Progressive Vision Loss: Without appropriate corrective lenses or other treatments, the cornea’s continuing deformation can lead to significant vision impairment.
- Acute Corneal Hydrops: This occurs when the cornea suddenly swells due to fluid from inside the eye leaking through the thinning cornea, causing sudden visual impairment and scarring.
- Corneal Scarring: Over time, the thinning cornea may scar, further impairing vision and potentially necessitating a corneal transplant.
- Challenges with Corrective Lenses: As the cornea becomes more irregular, it can be increasingly difficult to fit contact lenses, and glasses may no longer correct vision adequately.
Conclusion
Keratoconus is a progressive eye disorder characterized by the thinning and cone-like bulging of the cornea, which leads to distorted vision. While its exact causes are not fully understood, genetic factors, environmental influences, and behaviors like chronic eye rubbing are implicated in its development and progression. Early diagnosis is crucial for effective management, utilizing treatments that range from corrective lenses to surgical interventions like corneal cross-linking or transplants to halt progression and improve vision. Regular eye examinations are key to managing keratoconus, allowing for adjustments in treatment as the condition evolves. By adhering to recommended treatments and preventative measures, individuals with keratoconus can manage their condition effectively and maintain a good quality of life.