Keratoconus definition – An eye disorder characterized by an irregular corneal surface (cone-shaped)resulting in blurred and distorted images.
Keratoconus is a type of corneal dystrophy in which the normally dome-shaped cornea becomes thin and begins to bulge outward in a cone-like shape. Instead of the round shape of a healthy cornea, the cornea takes on a shape similar to that of the end of a football. Keratoconus is generally inherited, although it can occur with no family history of the disease and is associated with eye rubbing. Keratoconus usually begins development around puberty, but can also begin in the patient’s 20s.
According to the AAO, about 1/2000 people will develop keratoconus. Most people will have a mild or moderate form of the disease. Less than 10% of people with keratoconus will develop the most severe form. It typically is diagnosed in the late teens or twenties, however, many people have been diagnosed in their mid- to late-thirties. It is common for one eye to develop keratoconus faster than the other, and the eyes may go for long periods of time without any change–and then change dramatically over a period of months.
What causes keratoconus?
The cornea is made up of five different layers. The biggest layer, called the stroma, is made up of mostly water and collagen. Collagen, tiny fibers of protein, are responsible for maintaining the shape of the cornea. When the collagen fibers become weak the corneal shape cannot be maintained, and the eye begins to form a cone-like shape.
Keratoconus is caused by an insufficient number of protective antioxidants. The corneal cells emit harmful by-products, which are normally taken care of by the antioxidants. Without these antioxidants, the collagen fibers become weakened by the harmful by-products of the corneal cells.
What are the symptoms?
Keratoconus is usually a slowly progressing disease. Since this disease begins at a young age, chances are the beginnings of the disease will be caught during a routine eye examination. If keratoconus runs in your family, doctors will start running yearly or bi-yearly keratoconus tests starting at age 10.
Keratoconus affects both eyes, although the severity and timing can vary between each eye. Common symptoms of keratoconus include:
- Blurry vision
- Sensitivity to light
- Vision not correctable with glasses
Symptoms generally worsen as time goes on, and can sometimes develop rapidly. It is important to report any changes in your vision to your ophthalmologist.
While keratoconus has no outright cure, there are many treatment options. Here at OCLI, we understand that declining vision can be frustrating. We offer the most up-to-date treatments, technology, and research available to our patients living with keratoconus. There are two major concerns with keratoconus: first, stop the progression and second improve the vision.
Keratoconus vision improvement begins with a new eyeglass prescription. If eyeglasses do not provide adequate vision; contact lenses may be used. The type of contact lenses used with keratoconus are called rigid gas permeable contact lenses. Eventually, it may be necessary to seek other methods of treatment, such as surgery.
Intacs® Corneal Implants
Intacs® Corneal Implants are an ophthalmic medical device that can be used as a treatment for keratoconus, especially in those who do not tolerate contact lenses well. Intacs® are very thin plastic semi-circular rings. The Intacs® are inserted into the middle layer of the cornea, called the stroma. When inserted, the Intacs® works to flatten the cornea, reducing the effects of keratoconus.
Corneal cross-linking (CXL)
What is collagen cross-linking?
Corneal collagen cross-linking (CXL) is the only procedure that can strengthen the cornea to slow or stop the progression of keratoconus, protecting vision and delaying or potentially eliminating the need for a corneal transplant. This minimally invasive treatment increases the cornea’s collagen connections (cross- links), thus helping the cornea retain its firmness and shape. CXL has also been successful in treating patients with corneal ectasia, a steepening of the cornea that may occur as a complication of previous laser refractive surgery.
CXL has been used successfully in Europe and other countries for more than 15 years and has been approved in the United States for 6 years. OCLI’s team of corneal specialists was part of the original FDA clinical trial that showed excellent results and has over 12 years of experience. OCLI physicians have performed the most treatments of any group in the region.
How does CXL work?
Collagen is the structural protein that provides strength and firmness to our corneal tissue. CXL works by forming new cross-links between collagen fibers, which are the natural “anchors” within the cornea. These anchors are responsible for preventing the weakened cornea from bulging out and becoming steep and irregular. The addition of these “crossbeams” acts like adding rungs on a ladder to stiffen and strengthen the cornea, allowing it to focus light more efficiently and accurately.
How is CXL performed?
The procedure is performed in our office. First, you will be given anesthetic (numbing) eye drops to prevent discomfort. The corneal epithelium, a thin layer of clear, protective “skin” that covers the cornea, may be left in place, or partially or totally removed by the doctor, depending on the severity of the keratoconus. Next, vitamin B2 (riboflavin) eye drops are instilled in the eye, one drop every two minutes for 30 to 90 minutes. Next, a UVA (ultraviolet) light will be shined into your eye to “activate” the riboflavin, which causes the cross-linking of the collagen fibers. A soft contact lens may be placed on your eye immediately after the procedure, and antibiotic and steroid eye drops are then instilled.
How effective is CXL?
By strengthening collagen links, CXL is the first keratoconus treatment that goes to the root of the disease. Many research studies have shown that cross-linking prevents further vision loss, with many patients getting improved vision. As with many conditions, the earlier the condition is treated, the better the results.
If cross-linking is performed early, it may be possible to prevent the signs and symptoms of keratoconus in some eyes with “preclinical” keratoconus.
Can CXL prevent the need for a corneal transplant?
Many studies have shown that cross-linking can often prevent the need for a corneal transplant and allow patients to wear contact lenses or glasses more comfortably and safely again.
Can CXL be performed on anyone with keratoconus?
During your consultation, the doctor will determine if cross-linking might be an appropriate treatment option for you. Patients who have corneal scarring or whose corneas are too thin or too steep may not be good candidates for CXL. Patients who are female must not be pregnant or nursing.
How long does CXL treatment last?
Based on cross-linking results from more than a decade, the beneficial effects of CXL appear to last for a long time, and there is evidence that this strengthening effect may be permanent. In many studies, most patients respond to a single cross-linking treatment and do not need to have the procedure repeated. For the occasional patient in whom this treatment is not successful, cross-linking can be repeated.
A corneal transplant, also known as a corneal graft or a penetrating keratoplasty, involves the removal of the central portion (called a button) of the diseased cornea and replacing it with a matched donor button of cornea. Corneal grafts are performed on patients with damaged or scarred corneas that prevent acceptable vision. This may be due to corneal scarring from disease or trauma.
Deciding when to have a corneal transplant
A common indication for keratoplasty is keratoconus. The eye-care practitioner must decide when to recommend keratoplasty for the keratoconic patient. This is often not a simple, straight-forward decision. Keratoplasty for keratoconus is highly successful; however, there is a long recovery period and a risk of severe ocular complications. A number of factors must be considered in deciding when to do a keratoplasty. One of the most important is the patient’s functional vision. If the best acuity with their contact lenses prevents them from doing their job or carrying out their normal activities, a transplant must be considered. The actual measured visual acuity may be quite different for different patients. One patient may find that he/she can not do their job with 20/30 acuity while another patient may be very satisfied with 20/60 acuity.
Here at OCLI, we are committed to providing the best keratoconus treatment methods available today. If you have been diagnosed with keratoconus and would like to schedule an appointment with one of our cornea experts, call us today!
Reviewed by Eric D. Donnenfeld, MD