Keratoconus: Symptoms, Causes, Treatment

What are the symptoms of keratoconus?

Keratoconus is a progressive eye condition in which the cornea (the clear, dome-shaped front surface of the eye) thins and gradually bulges outward into a cone shape. This abnormal shape causes visual distortion. Symptoms of keratoconus can vary depending on the severity and stage of the condition, but they generally include:

1. Blurred or Distorted Vision: Vision becomes increasingly blurry and distorted due to the irregular shape of the cornea.
2. Increased Sensitivity to Light and Glare: Bright lights can cause discomfort and make it difficult to see, particularly at night.
3. Frequent Changes in Eyeglass Prescription: Rapid changes in the shape of the cornea often necessitate frequent updates to glasses or contact lens prescriptions.
4. Double Vision: Seeing double images, especially in one eye, can occur due to the irregular corneal surface.
5. Ghosting or Haloes around Lights: Seeing halos around lights or ghosting of images can be a sign of keratoconus.
6. Eye Strain and Headaches: Strain and discomfort from trying to focus can lead to headaches.
7. Difficulty with Night Vision: Night driving and seeing in low light conditions can become particularly challenging.
8. Distorted or Wavy Vision: Straight lines may appear wavy or bent, contributing to visual disturbances.
9. Sudden Worsening or Clouding of Vision: In advanced stages, the cornea can become scarred or swollen, leading to a sudden decrease in vision clarity.

The progression of keratoconus varies from person to person. In its early stages, symptoms might be mild and easily corrected with glasses or soft contact lenses. As the condition progresses, rigid gas permeable (RGP) contact lenses or other specialized lenses may be needed to correct vision. In advanced cases, corneal cross-linking, Intacs (corneal inserts), or corneal transplant surgery may be necessary to improve vision and stabilize the cornea. Regular eye examinations are crucial for early detection and management of keratoconus.

What are the causes of keratoconus?

The exact cause of keratoconus is not fully understood, but it is believed to result from a combination of genetic, environmental, and biomechanical factors. Some of the potential causes and contributing factors include:

1. Genetics: There is evidence to suggest that keratoconus can run in families, indicating a genetic predisposition. Certain genetic mutations and inherited conditions are associated with an increased risk of developing keratoconus.
2. Eye Rubbing: Chronic and vigorous eye rubbing has been linked to the development and progression of keratoconus. This mechanical trauma may weaken the corneal tissue over time.
3. Environmental Factors: Exposure to ultraviolet (UV) rays from the sun and other environmental factors may contribute to the weakening of the corneal structure.
4. Biochemical Abnormalities: Imbalances in the corneal enzymes and collagen cross-linking processes can lead to the weakening and thinning of the corneal tissue.
5. Inflammatory Conditions: Chronic eye inflammation, whether from allergies or other conditions, may play a role in the development of keratoconus.
6. Connective Tissue Disorders: Certain systemic conditions that affect connective tissue, such as Marfan syndrome, Ehlers-Danlos syndrome, and Down syndrome, have been associated with an increased risk of keratoconus.
7. Hormonal Factors: Hormonal changes during puberty and pregnancy may influence the progression of keratoconus, although the exact mechanisms are not well understood.
8. Contact Lens Wear: Poorly fitted contact lenses or prolonged wear of hard contact lenses may contribute to the development or worsening of keratoconus in susceptible individuals.

While these factors may contribute to the development of keratoconus, the condition’s precise etiology is likely multifactorial, involving an interplay of genetic susceptibility and environmental influences. Early detection and management are important to slow the progression of keratoconus and preserve vision.

How is the diagnosis of keratoconus made?

Diagnosing keratoconus involves a combination of medical history, visual acuity tests, and various eye examinations performed by an eye care professional, typically an optometrist or ophthalmologist. The diagnostic process includes:

1. Medical History and Symptoms: The doctor will ask about your symptoms, such as blurred or distorted vision, increased sensitivity to light, frequent changes in prescription, and any family history of keratoconus or eye disorders.
2. Visual Acuity Test: This standard eye test measures how well you can see at various distances to assess the impact on your vision.
3. Retinoscopy: In this test, the doctor shines a light into your eye and observes the reflection (reflex) off your retina. Irregular reflections can suggest keratoconus.
4. Slit Lamp Examination: This specialized microscope allows the doctor to examine the cornea’s surface in detail. Signs of keratoconus, such as corneal thinning, protrusion, or scarring, can be detected.
5. Keratometry: This test measures the curvature of the cornea. In keratoconus, the cornea typically shows an abnormal, cone-like shape rather than a regular dome shape.
6. Corneal Topography: This non-invasive imaging test maps the surface curvature of the cornea in detail. It provides a detailed map showing areas of steepening and thinning, which are characteristic of keratoconus.
7. Pachymetry: This test measures the thickness of the cornea. Keratoconus causes thinning of the cornea, which can be quantified with pachymetry.
8. Ocular Coherence Tomography (OCT): This imaging technique provides cross-sectional images of the cornea, allowing the doctor to evaluate its structure and detect any thinning or irregularities.
9. Wavefront Analysis: This advanced diagnostic tool measures how light waves travel through the eye. It can detect subtle irregularities in the cornea that are characteristic of keratoconus.

These diagnostic methods help confirm the presence of keratoconus and determine its severity. Early diagnosis is crucial for managing the condition and preventing further vision deterioration. If keratoconus is suspected, regular monitoring and appropriate treatment can help maintain vision and slow the progression of the disease.

What is the treatment for keratoconus?

The treatment for keratoconus depends on the severity of the condition and the progression of corneal thinning and irregularity. Here are the main treatment options:

1. Glasses or Soft Contact Lenses: In the early stages of keratoconus, mild visual impairment may be corrected with glasses or soft contact lenses. However, as the condition progresses and the cornea becomes more irregular, these options may become less effective.
2. Rigid Gas Permeable (RGP) Contact Lenses: RGP lenses are often the preferred option for correcting vision in moderate to advanced keratoconus. These lenses are rigid and provide a smooth refractive surface over the irregular cornea, improving vision clarity by creating a tear layer between the lens and the cornea.
3. Piggyback Lenses: In some cases, a soft contact lens can be worn under an RGP lens to improve comfort, especially if the RGP lens alone causes discomfort.
4. Scleral Contact Lenses: Scleral lenses are larger than RGP lenses and vault over the entire cornea, resting on the sclera (the white part of the eye). They provide better comfort and stability for irregular corneas in advanced keratoconus.
5. Hybrid Contact Lenses: These lenses combine a rigid center (like an RGP lens) surrounded by a soft peripheral skirt for improved comfort.
6. Corneal Cross-Linking (CXL): Corneal cross-linking is a minimally invasive procedure that aims to strengthen the corneal tissue and slow or halt the progression of keratoconus. It involves applying riboflavin (vitamin B2) eye drops to the cornea followed by exposure to ultraviolet (UV) light. This promotes the formation of bonds (cross-links) between collagen fibers in the cornea, enhancing its strength and stability.
7. Intracorneal Ring Segments (Intacs): Intacs are tiny, arc-shaped plastic inserts that are surgically placed into the cornea to flatten and reshape it, improving vision. This procedure is considered for patients who cannot tolerate or are not candidates for contact lenses.
8. Corneal Transplant (Penetrating Keratoplasty or PKP): In severe cases of keratoconus where vision cannot be adequately corrected with contact lenses or other treatments, a corneal transplant may be necessary. During this procedure, a surgeon replaces the diseased or distorted cornea with a healthy donor cornea.
9. Topography-Guided Conductive Keratoplasty: This is a newer treatment that uses radiofrequency energy to reshape the cornea based on topographic data, potentially improving visual outcomes in keratoconus patients.

The choice of treatment depends on factors such as the severity of keratoconus, the patient’s age, lifestyle, and preferences. Regular follow-up visits with an eye care professional are essential to monitor the progression of keratoconus and adjust treatments as needed to maintain optimal vision.