Corneal Associates, PC
840 Walnut Street
Philadelphia, PA 19107-5109
Keratoconus, sometimes abbreviated as KC, is a progressive, degenerative condition in which the cornea (the outer surface layer of the eye) protrudes and becomes cone-shaped, instead of round. This causes diminished vision brought on by scarring and an irregular surface of the eye.
Keratoconus typically develops between the ages of 12 and 25 and progresses for 10 to 20 years. It usually develops slowly, and many ophthalmologists miss its early signs. In its early stages, keratoconus causes slight blurring and distortion of vision, as well as increased sensitivity to glare and light. Keratoconus typically develops in both eyes, and while it does not cause blindness, it does cause significant visual impairment.
The causes of this condition are not known. It may have a genetic component and can be worsened by eye rubbing, and chronic eye irritation.
Patients with mild to moderate keratoconus can often achieve excellent vision with rigid, gas-permeable contact lenses. These hard contacts work because your tear fluid fills the gap between your irregular corneal surface and the smooth and regular inner surface of the lens. This mimics a smooth, regular cornea, thus improving your vision.
However, fitting a keratoconic patient for contact lenses is a delicate procedure and can require some trial and error. We can refer you to appropriate doctors who fit contact lenses both here at Wills and elsewhere.
Hard contact lenses may be necessary after corneal transplant surgery to improve vision. In this case, fitting a patient for contacts is much easier, as the patient is left with a more regularly-shaped cornea following transplant surgery.
Corneal Collagen Crosslinking Corneal collagen cross-linking is a technique which uses UV light and a photosensitizer to strengthen chemical bonds in the cornea. The goal of the treatment is to halt progressive and irregular changes in corneal shape known as ectasia. These ectatic changes are typically marked by corneal thinning and an increase in the anterior and/or posterior curvatures of the cornea, and often lead to high levels of myopia and astigmatism.
The primary goal of the first stage of therapy is to allow riboflavin to diffuse into the cornea. While there are several variations on the techniques used to accomplish this, all entail either removing or weakening the epithelial barrier of the cornea. In all instances the patient is first given anesthetic drops. Some ophthalmologists will also give preoperative antibiotics. A lid speculum is placed. After disrupting the epithelium, drops of riboflavin 0.1% (vitamin B2) are given at intervals of 1-5 minutes for 15 - 30 minutes, or until riboflavin can been seen in the anterior chamber of the eye by use of the blue filter on slit lamp examination. After adequate riboflavin absorption, the patient is positioned with the UV light (typically 365-370um) at a small distance (1-5cm) from the corneal apex for 30 minutes.
It is important to again note that the goal of Crosslinking is to stop progression of Keratoconus as it exists in the patient, not to reverse the condition.
In patients with more severe keratoconus, contact lenses may not be an effective treatment. In such cases, a corneal transplant (also known as penetrating keratoplasty) is often necessary. Corneal transplant surgery has the highest success rate of any transplant surgery in existence, and the success rate of corneal transplantation in patients with keratoconus is very good, with over 98 percent of patients gaining 20/40 vision (with correction). In cases where a corneal transplant does not drastically improve the patient’s vision, it will make contact lens fittings much easier.
The acute recovery period after surgery of this type is four to six weeks. Keratoconus rarely recurs in patients who have had a corneal transplant.
Since the cornea does not have a direct blood supply, the blood type of the donor does not have to be matched. Transplants involving donor corneas are much more successful than those with synthetic corneas, though some patients have conditions that require them to receive synthetic corneas.
Learn more about corneal transplants at Wills Eye Institute.
As ophthalmologists devoted to the study and health of the cornea, the Corneal Associates at Wills Eye Institute are uniquely suited to understand and treat keratoconus. If you suffer from this condition, there is no better place to seek treatment than Wills Eye Institute. Contact us today to schedule an appointment.
The National Keratoconus Foundation has good information about keratoconus and a support group for those affected by the condition.
The Eyebank Association promotes the gift of sight and aims to satisfy the large need for donor corneal tissue. About 100,000 corneal transplants are performed each year around the world, with over 90 percent turning out highly successful. However, the supply of donor corneal tissue has not yet met the demand.