What is Keratoconus?
Keratoconus is a condition in which the protein fibers that make up the cornea weaken, preventing the cornea from maintaining its shape. When this happens, the cornea (usually sphere-like in shape) can bulge in a cone-like shape and alter the way light enters the eye, causing visual distortion.
These changes to the cornea make it difficult for the eye to focus on its own, and typically require vision correction with a hard contact lens.
It is important to note that laser vision correction surgery – LASIK or PRK – can be dangerous for people who have keratoconus.
Ask the Doctor: What is the Best Treatment for Keratoconus?
Answer: Treatment should provide the best vision and prevent keratoconus from getting worse.
When they can be worn, contact lenses usually give the best vision. Contact lenses do nothing to prevent keratoconus from worsening, and, unfortunately, not everyone can tolerate contact lenses.
Intacs are permanent, surgically implanted, contact lens-like, corneal implants that usually provide some visual improvement in eyes unable to benefit from contact lenses that have mild-moderate keratoconus.
When keratoconus is newly diagnosed or progressing, and not extremely advanced, corneal cross-linking is a safe, effective treatment that prevents disease worsening.
Bowman layer transplantation is a sutureless procedure used when advanced keratoconus is still worsening or preventing the use of contact lenses. Bowman layer transplantation is effective at stopping the worsening of advanced keratoconus and can significantly improve the shape of a cornea with advanced keratoconus.
Sutured corneal transplants (full or partial thickness) are used only as a last resort. They don’t eliminate the need for contact lenses or the risk that keratoconus may continue to worsen.
- Causes of Keratoconus
- Symptoms of Keratoconus
- Diagnosis of Keratoconus
- Treatment of Keratoconus
While the causes of keratoconus are not entirely known, many doctors believe that genetics may play a part, since kerataconus tends to run in families. In fact, 10 percent of people with keratoconus have a family member who also has the condition.
Other factors that may play a role in the development of keratoconus include:
Excessive (chronic) eye rubbing
Injury to the eye
Long-term wear of hard contact lenses
Certain eye diseases, including retinitis pigmentosa, retinopathy of prematurity and vernal keratoconjunctivitis
Certain systemic conditions, including Down syndrome
Certain allergic conditions
Keratoconus can make wearing contact lenses virtually impossible.
Individuals with keratoconus usually begin to notice symptoms in their late teens or early 20s, often in both eyes simultaneously. The early symptoms of keratoconus can often mirror other eye conditions, such as myopia or cataracts.
These symptoms include:
- Mild blurring of vision
- Sensitivity to light
- Distortion of vision, in which straight lines look wavy
- Eye irritation, including redness or swelling
- Increased blurriness of vision
- More distortion in vision
- Double vision when one eye is closed
- Glare, halos or streaking around lights
- Frequent change in eyeglass prescription
- Inability to wear contact lenses due to pain
At Parker Cornea, we use the highest resolution Pentacam HR to map the front and back surface of the cornea and objectively assess the cornea’s clarity and optical properties.
Chances are you went to see your ophthalmologist or optometrist because you were not seeing as well as you used to see out of your glasses or contacts. But instead of simply getting a new prescription, you were diagnosed with a progressive, sight threatening condition. You probably left the office with questions such as- “What is keratoconus and what are my options?”
Keratoconus is a condition that causes the clear, normally sphere-shaped, front part of the eye to bulge forward into a cone-like protrusion. The front part of the eye, the cornea, thins as it protrudes and causes vision to blur.
Fortunately there are several options to help preserve and/or maintain your vision.
Option 1: Contact lenses
Blurred vision due to a bulging cornea is best corrected with a hard contact lens, but wearing a hard contact lens isn’t always easy, especially if you have keratoconus. The more the bulge, the more difficult it is to wear a contact lens; moreover, wearing a hard contact lens does not stop or slow the progression of keratoconus.
Option 2: Corneal cross-linking
Keratoconic corneas appear to be abnormally weak and flexible. A cornea can be made stronger and more rigid with a procedure called corneal cross-linking. Corneal cross-linking is best used when keratoconus is first diagnosed or only moderately advanced since its main effect is to arrest the progression of the corneal bulging.
Corneal cross-linking is an in-office procedure that has been proven to strengthen and stabilize corneas with early or moderate keratoconus. It received FDA approval in April, 2016 and can be used without or after Intacs implantation.
Option 3: Intacs®
Intacs are small, curved, permanent, plastic implants that are placed in the peripheral cornea. Intacs have proven to be an effective way to treat moderate keratoconus when vision can no longer be corrected with glasses or contact lenses.
Intacs have a special FDA approval, and the surgical procedure to implant them takes only a few minutes. The procedure usually improves vision by two or more lines on a standard eye chart. Intacs may not stop the progression of keratoconus and thus their implantation may be followed by corneal cross-linking.
Option 4: Bowman Layer Transplantation
As bulging becomes extreme, the cornea thins and cannot be effectively strengthened by cross-linking. Bowman layer transplantation is a sutureless procedure that can be used to strengthen and stabilize corneas that are too thin to cross-link.
Bowman’s layer is a very thin (10 micron), strong layer of specially organized collagen fibers just beneath the surface (epithelium) of the cornea. Disintegration of Bowman’s layer is the first microscopically observable change of keratoconus.
Transplanting an isolated Bowman layer from a normal cornea can strengthen a keratoconic cornea and reduce its bulging even in eyes with advanced progressing keratoconus. Bowman layer transplantation flattens the keratoconic cornea into a more normal position that makes it easier to wear contact lenses. Bowman layer transplantation is a sutureless procedure that is done in the operating theater.
Option 5: Corneal transplantation
Sutured corneal transplants have better success when used for keratoconus than in any other application. Even old studies demonstrate that about 95% of patients with keratoconus can achieve 20/40 or better vision with a corneal transplant, and new and improved methods of corneal transplantation (e.g., partial transplants) are now available to further improve keratoconus transplant outcomes.
Despite these positives, sutured corneal transplants are generally used only as a last resort in the treatment of keratoconus. A primary goal of modern techniques such as cross-linking, Intacs implantation, and Bowman layer transplantation is to preserve vision while avoiding the need for sutured corneal transplantation.