Keratoconus

Keratoconus is a progressive eye disease that causes the cornea to take on an irregular shape. Normally, the cornea is shaped like a dome, but if you have keratoconus, your cornea will become thin and bulge outward, becoming irregular and cone shaped. Since the cornea is responsible for refracting most of the light that comes into the eye, this irregular shape can cause significantly distorted vision.

Fortunately, keratoconus only occurs in 0.15% to 0.6% of the U.S. population, but it does tend to run in families. In most cases, keratoconus appears in the teenage years or in your early 20’s. It can affect one or both eyes and can progress quickly in some cases. For this reason, regular eye examinations are important, especially for people who have the condition or have a family history of keratoconus.

In most people, keratoconus will progress for 10-20 years and then stabilize. But certain medical conditions, including allergies, can cause keratoconus to progress more rapidly—possibly due to chronic eye rubbing. Generally speaking, each case is unique so there is no way to tell how each will progress or how severe it will become.

What Causes Keratoconus?

Research suggests that keratoconus may be caused by an imbalance of proteins within the cornea. This imbalance causes the corneal tissue to weaken and bulge forward in response to oxidative damage from free radicals.

Excessive eye rubbing, a history of poorly fit contact lenses and chronic eye irritation are also associated with keratoconus.

Although you are more likely to develop keratoconus if someone in your family also has the disease, current research indicates that there is less than a one in ten chance that a blood relative of a keratoconic patient will have keratoconus. However, since there is a genetic link, children with family members who have keratoconus should start having their eyes checked for keratoconus starting at age ten.

A new study of more than 32,000 people, half of whom had confirmed keratoconus, has recently shed new light on other potential risk factors. In the largest keratoconus study conducted to date, researchers at the University of Michigan’s Kellogg Eye Center and Institute for Healthcare Policy and Innovation have found an increase in keratoconus in the following populations:

  • Men, specifically of African-American or Latino descent.
  • Asthma
  • Sleep apnea
  • Down syndrome

 

How Is Keratoconus Diagnosed?

Keratoconus usually develops slowly, making it difficult to detect in its earliest stages. Some of the first signs that you may notice are slight blurring or visual distortion in addition to an increased sensitivity to glare and light. Another potential sign of keratoconus is a large change in glasses prescriptions from year-to-year. Generally, you’ll become more nearsighted—meaning far-away objects will be harder to see.

If keratoconus is suspected, your doctor will measure the shape of your cornea with a special instrument called a corneal topographer, which noninvasively captures a photo of your eye and generates a map of its surface, revealing any irregularities. The recent advances in this technology allow for early detection of the disease and more customized management strategies.

Scleral Lenses for Keratoconus

If you have mild keratoconus, doctors may be able to correct your vision with eyeglasses or soft contact lenses. However, as the corneal irregularities become worse with disease progression, these options may fail to provide suitable vision. At this stage, other types of contact lens fitting systems are generally more effective. These include gas permeable (GP) lenses, commonly referred to as “rigid” or “gas permeable” lenses, which allows them to act as the primary optical surface of the eye and mask the underlying corneal surface irregularities.

A scleral lens is a type of GP lens, featuring a large-diameter that allows the lens to rest on the white part of the eye, known as the sclera. Unlike traditional, small diameter GP lenses that rest on the highly innervated and sensitive cornea, the scleral lens vaults over the cornea and is much more comfortable than its smaller diameter counterpart. Since the emergence of modern scleral lenses approximately 15 years ago, they have gained increasing utility amongst doctors and patients due to their high level of comfort and visual stability.

Surgical Treatments and Interventions for Keratoconus

There are also a number of surgical options for the management keratoconus, including intracorneal ring segments such as Intacs, corneal transplantation, and corneal collagen crosslinking. The goals of these treatments are generally to reduce

the effects of scarring and potentially slow the progression of the disease. These treatments can be quite helpful in the management and disease stabilization of keratoconus, although patients often still need specialty lens correction in the form of a scleral lens.

If you have keratoconus, visit your eye doctor to determine the most appropriate management strategy for you.