Keratoconus - Causes, Symptoms and Treatments
Keratoconus:
Keratoconus is a relatively common (about 1 in 1000 people) degenerative eye disorder. This disorder is characterized by a thinning of the cornea, the transparent layer on the front of the eye. As the cornea thins, it becomes conical in shape. Keratoconus can cause a number of visual distortions including blurred vision, multiple ghost images, streaking around light sources and light sensitivity. In addition, poor visual acuity and poor night vision are common symptoms of this disorder. Keratoconus is the most common type of corneal dystrophy and is commonly treated by corneal specialists like Dr. Ilan Cohen from the Fifth Avenue Eye Center.
(Normal Cornea on the left/Keratoconus on the right.) In Keratoconus the eye's cornea is shaped like a footbal rather than a basketball.
Topography in Keratoconus shows inferior steepening
Keratoconus Symptoms:
Keratoconus usually starts off with mild symptoms and is most commonly diagnosed in the teenage years. Usually it appears as astigmatism just after the onset of puberty. Patients may notice their visual acuity rapidly worsening, which often sparks further examination. This is a progressive disorder, but the progression is variable. Some people experience visual stability for years and other have bursts of rapid progression. In general, the disease usually progresses for 10 to 20 years before becoming stable. Most patients who are over 40 years old will have stable vision.
Treatment Options:
For most people with keratoconus, corrective lenses provide enough visual correction to function normally. Early on, soft contact lenses can be an effective keratoconus treatment to correct astigmatism. As the disorder gets worse, however, most patients need to switch to rigid gas permeable contact lenses (RGPs). The cone-shape of the cornea makes soft contact lenses less effective. With rigid contact lenses, tear fluid can fill the space between the misshaped cornea and the underside of the lens and produce the effect of a flatter cornea. There are a variety of different contact lenses that are specially designed for those with keratoconus. Fitting contact lenses for those who have keratoconus can be difficult and may require some trial and error by the fitter and the patient.
Many of those who suffer from keratoconus will become contact lens intolerant as the disorder progresses. The RGPs can become more and more uncomfortable as the cornea becomes more conical. One cause of discomfort can be scar tissue developing on the part of the cornea that touches the contact lens. At this point, surgical options become necessary. Presently there are two main surgical keratoconus treatment options. The oldest of these treatments is the corneal transplant, also called penetrating keratoplasty.
Corneal Transplants:
Corneal transplants are commonly used when scarring has developed from wearing contacts. In a corneal transplant, part of the patient’s cornea is cut out and donor corneal tissue is grafted onto the eye. Corneal transplants are the most common transplant procedure in the U.S., and they have a success rate of over 95% as a keratoconus treatment. The procedure itself is typically done as an outpatient procedure under sedation, but typically a four to six week recovery period can be expected. It can take up to a year for visual acuity to stabilize completely following a corneal transplant, but once the eye has stabilized it should remain stable in the long term. The main complications of corneal transplants are rejection of the corneal tissue and infection of the eye. Both of these complications can be mitigated with prophylactic medications.
Some patients who undergo a corneal transplant can have clear vision restored, but others may not see well even after the transplant. For these patients, it is possible to treat visual acuity problems with contact lenses or glasses. The corneal transplant flattens the cornea and can correct contact lens intolerance. If contact lens intolerance remains a problem, some patients may be candidates for laser eye surgery to give them near perfect vision.
Intacs for Keratoconus:
Another surgical keratoconus treatment that is less invasive than corneal transplantation is the use of corneal ring segment inserts known as Intacs. The procedure only takes a matter of minutes and is done as on an outpatient basis. The implantation of these inserts flattens the conical cornea in keratoconus patients to improve vision and increase contact lens tolerance. The procedure involves creating channels in the cornea with a laser or mechanical spreader and inserting one or two crescent-shaped segments made of Plexiglas into those channels. The tunnels are then closed. This procedure is routinely performed by cornea specialists like Dr. Ilan Cohen of the Fifth Avenue Eye Center and has very little risk of complications. Opting to have an Intacs procedure can prevent those with keratoconus from needing a cornea transplant in the future.
Collagen Cross Linking for Keratoconus:
Collagen cross linking is another newer keratoconus treatment option. It can be used with or without Intacs. This treatment involves applying riboflavin drops to the cornea and then exposing the cornea to UVA light. The process increases collagen cross linking and improves corneal strength. Early studies have shown this treatment may halt the progression of keratoconus and flatten the cornea to some degree. A visit to Dr. Ilan Cohen at Fifth Avenue Eye Center can provide you more details about the various keratoconus treatment options and which ones may be right for you.
