Keratoconus

What is keratoconus?

Keratoconus is characterized by the thinning of the cornea and irregularities of the cornea’s surface. The cornea is the clear, outer layer at the front of your eye. The middle layer is the thickest part of the cornea, mostly made up of water and a protein called collagen. Collagen makes the cornea strong and flexible and helps keep its regular, round shape. This healthy cornea focuses light so you can see clearly. With keratoconus, the cornea thins and bulges into an irregular cone shape, resulting in vision loss.

Keratoconus generally begins at puberty and progresses into the mid-30s. There is no way to predict how quickly the disease will progress, or if it will progress at all. Keratoconus typically affects both eyes, with one being more severely affected than the other.

What causes keratoconus?

Although keratoconus has been studied for decades, it remains poorly understood. The definitive cause of keratoconus is unknown, though it is believed that the predisposition to develop the disease is present at birth. A common finding in keratoconus is the loss of collagen in the cornea. This may be caused by some imbalance between production and destruction of the corneal tissue by the corneal cells.

What are the symptoms of keratoconus?

Many keratoconus patients are unaware they have the disease. The earliest symptom is a slight blurring of vision or progressively poor vision that is not easily corrected.

Other symptoms of keratoconus include:

• Glare and halos around lights
• Difficulty seeing at night
• Eye irritation or headaches associated with eye pain
• Increased sensitivity to bright light
• Sudden worsening or clouding of vision

What are the risk factors for keratoconus?

The following may increase the risk of developing keratoconus:

• Genetics: Patients with a family history of keratoconus or with certain systemic disorders, such as Down syndrome, are at a higher risk of developing keratoconus.
  
  
• Chronic eye inflammation: Constant inflammation from allergies or irritants can contribute to the destruction of corneal tissue that may result in developing keratoconus.
  
  
• Eye rubbing: Chronic eye rubbing is associated with developing keratoconus. It may also be a risk factor for disease progression.
  
  
• Age: Keratoconus is often discovered in the teenage years. Generally, young patients with advanced keratoconus are more likely to need some form of surgical intervention as the disease progresses.

How is keratoconus diagnosed?

In addition to a complete medical history and eye exam, your eye care professional may perform the following tests to diagnose keratoconus:

• Corneal topography. This is the most accurate way to diagnose early keratoconus and follow its progression. A computerized image is taken that creates a map of the curve of the cornea.
• Slit-lamp exam. This examination of the cornea can help detect abnormalities in the outer and middle layers of the cornea.
• Pachymetry. This test is used to measure the thinnest areas of the cornea.

How is keratoconus treated?

Treatment of keratoconus focuses on the correction of vision and depends on the stage of the disease.

Early Stages

Current treatment for keratoconus includes glasses in the earliest stages to treat near-sightedness and astigmatism. As keratoconus progresses and worsens, glasses are no longer capable of providing clear vision, and patients need to wear a contact lens, usually a hard contact lens.

Intermediate Stages

Progressive keratoconus can be treated by corneal collagen cross-linking. This one-time, in-office procedure involves the application of a vitamin B solution to the eye, which is then activated by ultraviolet light for about 30 minutes or less. The solution causes new collagen bonds to form, recovering and preserving some of the cornea’s strength and shape.

While the treatment cannot make the cornea entirely normal again, it can keep vision from getting worse and, in some cases, may improve vision. The procedure may require the removal of the thin outer layer of the cornea (epithelium) to allow the riboflavin to more easily penetrate the corneal tissue.

Cross-linking was approved as a treatment for keratoconus by the FDA in April 2016, after clinical trials showed that it stopped or produced a mild reversal in bulging of the cornea within three to 12 months after the procedure.

Advanced Stages

• Corneal ring: With severe keratoconus, a standard contact lens may become too uncomfortable to wear. Intacs are implantable, plastic, C-shaped rings that are used to flatten the surface of the cornea, allowing improved vision. They may also allow a better contact lens fit. The procedure takes about 15 minutes.
  
  
• Corneal transplant: In a corneal transplant, a donor cornea replaces the patient’s damaged cornea. Corneal transplants are often performed on an outpatient basis and take about an hour to complete. Vision usually remain blurry for about three to six months after the transplant, and medication must be taken to avoid transplant rejection. In almost all cases, glasses or a contact lens are necessary to provide the clearest vision after transplant surgery.

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