Keratoconus is a progressive eye disease in which the normally round cornea 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 can occur in one or both eyes and often begins during a person’s teens or early 20s.
Keratoconus signs and symptoms
As the cornea becomes more irregular in shape, it causes progressive nearsightedness and irregular astigmatism to develop, creating additional problems with distorted and blurred vision. Glare and light sensitivity also may occur.
Often, keratoconic patients experience changes in their eyeglass prescription every time they visit their eye doctor.
What causes keratoconus?
Research suggests the weakening of the corneal tissue that leads to keratoconus may be due to an imbalance of enzymes within the cornea. This imbalance makes the cornea more susceptible to oxidative damage from compounds called free radicals, causing it to weaken and bulge forward.
Risk factors for oxidative damage and weakening of the cornea include a genetic predisposition, explaining why keratoconus often affects more than one member of the same family.
Keratoconus also is associated with overexposure to ultraviolet rays from the sun, excessive eye rubbing, a history of poorly fitted contact lenses and chronic eye irritation.
In the mildest form of keratoconus, eyeglasses or soft contact lenses may help. But as the disease progresses and the cornea thins and becomes increasingly more irregular in shape, glasses and regular soft contact lens designs no longer provide adequate vision correction.
Treatments for progressive keratoconus include:
1. Corneal crosslinking
This procedure, also called corneal collagen cross-linking or CXL, strengthens corneal tissue to halt bulging of the eye’s surface in keratoconus.
The aim of corneal cross-linking is to strengthen the cornea by increasing the number of “anchors” that bond collagen fibers together. (Diagram: Boxer Wachler Vision Institute)
There are two versions of corneal crosslinking: epithelium-off and epithelium-on.
With epithelium-off crosslinking, the outer layer of the cornea (called the epithelium) is removed to allow entry of riboflavin, a type of B vitamin, into the cornea, which then is activated with UV light.
With the epithelium-on method (also called transepithelial crosslinking), the corneal epithelium is left intact during the treatment. Advantages include less risk of infection, less discomfort and one-day visual recovery.
Avedro’s Photrexa/KXL System currently is the only FDA-approved platform and procedure for corneal crosslinking treatment of progressive keratoconus in the United States. However, eye surgeons can lawfully use other riboflavin/UV light crosslinking protocols to perform less invasive, epithelium-on crosslinking treatment for keratoconus — such as the Holcomb C3-R crosslinking procedure.
Corneal crosslinking may reduce significantly the need for corneal transplants among keratoconus patients. It also is being investigated as a way to treat or prevent complications following LASIK or other vision correction surgery.
Using a combination of corneal crosslinking and Intacs implants also has demonstrated promising results for treating keratoconus. Also, progressive mild to moderate keratoconus has been safely and successfully treated with a combination of corneal crosslinking and implantation of a toric phakic IOL.
2. Custom soft contact lenses
Recently, contact lens manufacturers have introduced custom soft contact lenses specially designed to correct mild-to-moderate keratoconus. These lenses are made-to-order based on detailed measurements of the person’s keratoconic eye(s) and may be more comfortable than gas permeable lenses (GPs) or hybrid contact lenses for some wearers.
In the United States, custom soft contacts that are available for the correction of keratoconus include:
- KeraSoft lenses (Bausch + Lomb). These high-water silicone hydrogel lenses can correct up to 20 (D) of nearsightedness or farsightedness and up to -12 D of astigmatism.
- NovaKone lenses (Bausch + Lomb). These medium-water hydrogel lenses can correct up to 30 D of nearsightedness or farsightedness and up to -10 D of astigmatism.
Both lenses have a very wide range of fitting parameters for a customized fit and are larger in diameter than regular soft lenses for greater stability on a keratoconic eye.
Custom toric soft contacts for keratoconus are significantly more expensive than regular soft contacts, but vision insurance may cover some of the costs associated with contact lenses for keratoconus.
3. Gas permeable contact lenses
Because eyeglasses and soft contact lenses often cannot provide adequate visual acuity in cases of keratoconus, gas permeable contact lenses usually are the preferred treatment. GP lenses vault over the cornea, replacing its irregular shape with a smooth, uniform refracting surface to improve vision.
Fitting contact lenses on an eye with keratoconus often is challenging and time-consuming. You can expect frequent return visits to your eye care provider so he or she can fine-tune the fit and your prescription, especially if your keratoconus continues to progress.
FDA-APPROVED CORNEAL CROSS-LINKING
For progressive keratoconus, only Avedro’s corneal cross-linking procedure is FDA approved and widely covered by insurance.
In 2016, Avedro’s corneal cross-linking procedure became the first and only FDA approved corneal cross-linking treatment for progressive keratoconus. Since then, the procedure has been completed more than 18,000 times at more than 300 practices nationwide.
Today, the treatment is widely covered by commercial insurance. Click here to view your insurance policy
Supported by the National Keratoconus Foundation, this safe, minimally invasive outpatient procedure works by stiffening the weakened cornea to slow or halt progression of the disease.
Make sure your cross-linking is FDA-approved and covered by insurance.