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What is Keratoconus?

Keratoconus_profile_sm.jpgProfile photo of patient with Keratoconus is a progressive thinning of the cornea.  The cornea is the clear, front window of the eye, which, along with the intra-ocular lens, focuses light onto the retina.  The cornea normally is a smooth, round dome-like shape, however in keratoconus, the cornea becomes very thin, irregular, and starts to protrude from the center or just below the center like a cone.  This causes blurry vision that is often not correctable with glasses. Keratoconus usually involves both eyes, however one eye may be more advanced than the other.

What are the Symptoms of Keratoconus?

Typically blurred vision that cannot be corrected with glasses is the first symptom of keratoconus.

What Causes Keratoconus?

Keratoconus is one of the most common corneal dystrophies in the U.S., affecting one in every 2000 Americans.  It is more prevalent in teenagers and adults in their 20s.

Studies indicate that keratoconus stems from several possible causes:

  1.  An inherited corneal abnormality. About 7% of those with the condition have a family history of keratoconus.
  2. An eye injury, i.e., excessive eye rubbing.
  3. Keratoconus has been associated with certain eye diseases, such as retinitis pigmentosa, retinopathy of prematurity and vernal keratoconjunctivitis.
  4. Systemic diseases, such as Leber's congenital amaurosis, Ehlers-Danlos Syndrome, Down syndrome, and osteogenesis imperfecta have been associated with keratoconus.


How is Keratoconus Treated?

Contact lenses are the treatment of choice for keratoconus.  Over 90% of patients with keratoconus will be successfully treated with contact lenses.  In the early stages of keratoconus your vision can often be corrected with eyeglasses, however, as the corneal thinning worsens we must rely on specially fitted contact lenses to reduce the distortion and provide better vision.

At Total Eye Care we have a great deal of experience in fitting patients with advanced keratoconic contact lens designs.  The fitting process involves making a topographical map of your cornea.  A topographical map allows us to see the exact size and position of your “cone”.  Topographical Keratoconus_1.jpgmap of an eye with keratoconusBy using corneal topography we can design a contact lens that will provide much better vision and comfort than traditional contact lenses.  Corneal topography also allows us to fit lenses that we design on a computer.  With the aid of a computer we can see how the contact lens, we design for you, will fit on your eye before we even order it!  In almost every case it will take more than one diagnostic lens to achieve an optimal fit.  Special curves on the back surface of the lens are needed to fit over the pointed area of the cone.  This typically requires numerous office visits and lens adjustments to accomplish.  Patients with keratoconus have more sensitive corneas and some awareness of the lens is not uncommon during the early fitting of the lens.  First time lens wearers may require an adaptation period before good comfort is attained.

New Contact Lens Treatment Options

Recently, a few new types of keratoconic lenses have come available.  The first brings together the visual acuity of a gas permeable lens and the comfort of a soft lens.  This new lens is called the SynergEyes lens.  It uses a small gas permeable lens surrounded by a soft lens skirt.  Synergeyes lenses can actually be used for any contact lens patient, however we have found it to be especially helpful not only for patients with keratoconus but also irregular astigmatism, pellucid marginal degeneration and patients that were unsuccessful with RK, LASIK or PRK.

Mini scleral lenses are another relatively new option for keratoconic patients as well as patients with irregular corneas from refractive surgery.  A mini scleral is about the size of a small, soft contact lens making it a comfortable lens to wear.  Patients often states it is almost as comfortable as a soft lens.  This increased comfort over traditional gas permeable lenses is due to its size.  The upper edge of a mini scleral lens sits under the upper eyelid giving much better comfort when a patient blinks.

In most cases, the cornea will stabilize after a few years without ever causing severe vision problems.  The vast majority of patients with keratoconus are best treated with the new hybrid contact lenses or gas permeable contact lenses.  In about 10% of patients with keratoconus, the cornea will eventually become too scarred or will not tolerate a contact lens.  If either of these problems occur, a corneal transplant may be needed. This operation (penetrating keratoplasty) is successful in more than 90 percent of those with advanced keratoconus. Several studies have also reported that 80 percent or more of these patients have 20/40 vision or better after the operation.  In some cases a contact lens is necessary to achieve the best visual acuity following a corneal transplant.

Corneal Cross Linking

Corneal cross linking (CXL) is the newest development in the treatment of keratoconus and as such it holds a lot of promise.  Quite simply, CXL involves treating the cornea with riboflavin and then activating its collagen cross linking properties with ultraviolet light.  CXL improves the strength of the cornea by increasing the linking between collagen fibers. The result of this increased cross linking is that it increases the strength of the cornea and often causes some corneal flattening.  Currently, CXL is available on an experimental basis in the United States as it goes through the FDA approval process.

What Research is Being Done About Keratoconus?

The National Eye Institute is conducting a natural history study--called the Collaborative Longitudinal Evaluation of Keratoconus Study (CLEK) to identify factors that influence the severity and progression of keratoconus.

What Can I do to Prevent My Keratoconus From Getting Worse?

The single most important thing for you to do is to have us evaluate the fit of your contact lenses every 6-12 months.  We will do a complete eye exam (dilated with corneal topography) every year and every 6 – 12 months we will evaluate the fitting relationship between your contact lens and your cornea.  A poorly fitting contact lens may cause additional scarring, therefore it is best for us to evaluate your contact lenses regularly.

Having a pair of glasses that you can see well enough to drive and that you don’t mind being seen wearing them in public is also important.  You will probably see better with your contacts than your glasses, however, there are times when your eyes need a break and if you hate your glasses you are less likely to give your eyes that much needed break.

What Can I Expect Over the Coming Years?

For the vast majority of patients the fact that they have keratoconus will not negatively affect their daily life.  Having keratoconus means you will need regular eyecare, as discussed above.  It also means that the best vision you can attain with your glasses will likely not be as good as that vision you achieve with your contacts.  Over the years your vision will fluctuate just like everyone else’s.  There are very few occupations that would be unavailable to a person with keratoconus.  If you have any questions or require additional information, please do not hesitate to ask us.  We are here to help.

More information about keratoconus can be found at AllAboutVision.com - Keratoconus.
 
Portions of this document were adapted, with permission, from the National Eye Institute document Keratoconus.