Keratoconus (KC) is a thinning of the cornea that can significantly impair vision. Instead of being round and smooth, it bulges at its thinnest point which causes distortion and warpage as shown in the pictures below. It usually affects both eyes, but at different degrees. This distortion has been compared to viewing a street sign through your car windshield during a very bad rain storm. Its progression is generally slow and can stop at any stage from mild to severe. As KC progresses, the cornea becomes thinner and bulges even more producing more distortion and scarring. Usually vision, can only be fully corrected with rigid or scleral contact lenses. Glasses and soft lenses usually only provide partial correction.

The role of the Cornea

Light enters the eye through the cornea, which is the clear dome covering the colored part of the eye (iris). You cannot see the cornea except if it is scarred. Contact lenses are fit and rest on this part of the eye. It is the cornea that focuses the visual images to travel and hopefully focus on the back of the eye. If either the smoothness or the clarity of the cornea suffers, vision will be bluirred. Minor scaring on the cornea from KC can permanently impair one's vision.

Cause of keratoconus

The bulging or thinning of the cornea from keratoconus (KC) is from a weakened collagen layer in the cornea, resulting in distorted vision. It is estimated to be prevalent in 1 out of 2000 patients. The cause is still unknown, however there are a few theories.

1. Genetic:
This would make sense. However, we have treated hundreds of KC over the years and have never seen it passed down to offspring.

2. Degenerative:
This also has merit as KC can start in the late teens and progress from there.

3. Secondary to some other disease process:
We have seen KC associated with patients that have lots of allergies and have a need to vigorously rub their eyes.

4. Involvement of the endocrine system:
A less likely held hypothesis but has gained some credence due to the usual appearance of KC at puberty.

At the end of the day, no one really knows the exact cause of Keratoconus.

Bulging cornea due to thinning and weakening, causes distortion that can be usually corrected with a rigid gas permeable, scleral or hybrid contact (RGP center, soft periphery) contact lens. There are newer soft lens technologies that can provide good vision and comfort.

Signs and Symptoms

KC starts out causing blurred vision. Initially, it may be corrected with glasses. The continued thinning of the cornea from weakened collagen will make it harder to correct with glasses. This progression tends to last for 5 to 10 years and then levels off. Occasionally, if there is rapid progression, scarring can develop which can impair vision even with contact lenses. In the advanced stage, the patient may experience a sudden clouding of vision in one eye that clears over a period of weeks or months. This is called "acute hydrops" and is due to the sudden infusion of fluid into the stretched cornea. Severe scarring would require a corneal transplant to restore good vision.

KC treatment

Initially, ordinary eyeglasses or soft lenses may correct the blurred vision. As the disease advances, custom contact lenses may be the only way to provide 20/20 viision. If fit properly, patients can see and function normally throughout their life. Annual or bi-annual evaluations are needed to maintain good vision and a healthy cornea. With KC, the cornea can change shape altering the fit of the contact lens. An ill-fiting lens can cause damage to the cornea. Contact lens designs that may be used are:

These are the prior "hard lenses" except they are now make with special oxygen permeable material that allows the cornea to breathe. They are smaller and are fit directly onto the cornea. This is the most widely used treatment as they are the most cost effective and still provide excellent safety and vision.

Due to advances in manufacturing, specific rigid gas permeable materials can be made larger like a soft lens. These lenses vault over the corneal and fit on the sclera (white of the eye), to provide excellent vision and soft lens comfort.

These lenses have a smaller RGP in the center attached to a larger soft lens skirt in the periphery for better comfort and fit.

Piggyback:
This is a longstanding design of fitting an RGP on top of a soft lens. This is often successful when all other options have failed.

It should be noted that technological advances in both gas-permeable materials and manufacturing offer more and more possibilities for keratoconus patients.

Cornea-Crosslinking

This is a relatively new procedure that uses Riboflavin and ultravilet light to strengthen the cornea cells. This can not cure KC, but it can stop it progressing to a more advanced form. This is performed by a corneal specialist and is usually not covered by inurance. Results have been very good.

​​​​​​​Corneal Transplant

Corneal transplantation is considered only in those cases in which contact lenses cannot be worn or provide inadequate vision despite the most skilled efforts. Only about 5% of KC cases require corneal transplant surgery. Either general or local anesthesia can be used in this procedure. Most people experience surprisingly little pain or discomfort following the surgery. Time off work will vary with individuals and the kind of work they do. Generally, with a sedentary job, the patient should be back to work in a few days to a couple of weeks. Eye banks in major cities collect healthy corneas from decedents to be used for this procedure. This is a highly sophisticated system, enabling corneal transplants to be 95% successful. The probability of rejection on the eye is much less than that of any other transplanted organs because the cornea has no blood vessels.

The surgeon uses high-tech instrumentation to remove the distorted cornea and to cut out a similar "button" from the donor cornea. Looking through a surgical microscope, the surgeon places the donor cornea button in the round hole of the patient's cornea and stitches them together with sutures much finer than human hair. Complete healing time takes nine to twelve months before vision stabilizes. Patients will always be left with a moderate to large degree of astigmtiam, requiring the use of contact lenses or eyeglasses to provide maximum vision.