Keratoconus is an eye disease in which the cornea of the eye becomes thin and bulges forward causing distortion to the optics of the eye. The cornea of the eye is the most powerful light bending surface of the eye and distortion to this surface can have a devastating effect on the clarity of vision. There has been a great deal of research into the causes of keratoconus and it's treatment. The purpose of this post is to discuss the disease, its various stages and the treatment options that are available.
In the early stages of keratoconus treatment can be relatively simple. When there is not a great deal of distortion to the cornea, eyeglasses and soft contact lenses can often provide good vision. As the disease progresses there is a decrease in what is known as "best corrected vision". This means that as the cornea becomes more irregular, eyeglasses and soft contact lenses may begin to no longer afford the patient the sharpenss to their vision that they had previously enjoyed. Different methods need to be employed to restore or to help capture a sharper image on the retina (the back of the eye). Here is an analogy: Imagine that you have a brand new camera. In the camera you have excellent quality film. At first the camera takes great pictures. Slowly, over time, you notice that the pictures are becoming fuzzy and not clear. The film is great, in this example, but a defect has occurred to the front part of the lens in the camera. The surface had become irregular, perhaps because the lens became scratched. Because of this irregular surface on the front of the camera, the images are no longer clear. This is what happens to the human eye when the cornea becomes distorted. In the human eye, the surface of the cornea actually becomes irregular and uneven....not scratched as in the camera analogy....but this irregularity distorts the images that are formed on the retina (the retina is the back of the eye that is similar to the film in a camera in this example).
As the cornea becomes more and more distorted, something has to be done to improve the surface quality of the cornea. Eyeglasses can still be worn, but the clarity of the vision becomes poorer and poorer. To restore this optical quality to the eye, rigid contact lenses are used. The reason that rigid contact lenses improve the quality of the image on the retina is that they become a new front surface for the eye. They are made from a rigid material and when placed on the eye, the area between the back surface of the rigid lens and the front surface of the cornea (which is now irregular and distorted) fills in with a patient's own tears. Optically speaking, the new front surface of the cornea is now the front surface of the rigid contact lens. Because it is smooth and regular it erases the distortion present on the natural corneal surface and light passes through to the retina causing a sharp and defined image to be formed on the retina, thereby returning sharp vision to the eye.
How are rigid contact lenses fitted to the cornea in keratoconus? This is a very complicated subject. Depending upon the degree of distortion to the cornea different types of rigid contact lenses can be used to improve the vision. First, the degree of distortion of the eye is measured by devices that can map or determine the shape of the corneal surface. Then the eye doctor or contact lens fitter has to try different lenses on the eye to determine which type of lens will best fit the cornea and the surrounding tissues. To do this, the eye doctor or contact lens fitter has to try on many different types of lenses. To be successful, a large inventory of diagnostic lenses must be available. In keratoconus contact lens fitting there is no such thing as one size fits all. Every cornea is different. Sometimes small contact lens designs work and sometimes larger lenses need to be employed. It is common to try on lenses from many different manufacturers before settling upon a lens design that is correct for the individual patient. It is important for the patient to understand that the fitting of contact lenses for keratoconus is a process. It requires many visits over a period of time. Even after the best fit and vision is determined by the contact lens fitter, the lens needs to be custom ordered. Once the lenses come back to the office and are verified to be correct they then need to be seen on the patient's eyes. The quality of the fit is determined by using a special diagnostic dye that will spread through the patient's tears and collect behind the contact lens. (This same dye is used in the initial fitting process as well.) The dye will glow when exposed to a special light that the doctor will shine on the eye to determine the best fit. By observing how the tears collect behind the lens the doctor can assess the quality of the fit. Once it is determined that the fit is proper, the vision is measured as well. If everything goes according to plan, both the vision and the fit are what was expected. The patient is trained on the care and handling of the products and is asked to begin wearing the lenses on a schedule that gradually increases the wearing time until the patient is able to work up to a full day of wear. After using the lenses for a period of time the patient is asked to return to further assess the quality of both the fit and the vision. It is common for both the fit and the power of the lenses to be modified on the first follow up visit. This may not be necessary, but it is a common scenario as the lenses can "settle" on the eye after using them for awhile requiring a modification in the fit of the lenses. New lenses are then ordered. It is helpful if the fitter or the doctor has the ability to modify the lenses in the office. If this is possible, many of the minor adjustments can be done on the premises rather than off site. This makes is easier to "fine tune" the fit for the patient.
After reading all of the above information it is easier to understand that the fitting of contact lenses for keratoconus is indeed a process. What should the keratoconus patient look for when choosing a doctor or contact lens fitter to help them with obtaining properly fitting contact lenses?
Here are some suggestions: 1. Make sure the person fitting the lenses has lots of experience in fitting lenses specifically for keratoconus. 2. Make sure the fitter has many different fitting sets....remember that one size does not fit all eyes. 3. If possible, make sure the fitter can do contact lens modification is the office when appropriate. 4. Make sure that you are comfortable with the fitter and the office. You will be spending quite of bit of time at the office. It is no fun being in an office where you do not feel welcome.
Keratoconus can take different forms. While it is supposed to be a condition in which both eyes are involved, this is not always the case. Sometimes, only one eye is affected. Some cases continue to deteriorate, requiring refitting of the contact lenses. Some cases deteriorate to the degree that the cornea needs to be replaced. This is called a corneal transplant. Not all cases get to this point. Some cases never progress to the point where contact rigid contact lenses are required. Corneal transplant surgery is getting better all the time. There are many excellent surgeons that can help patients when their eyes get to the point that the cornea needs to be replaced. When a transplant is needed, this is due to either scarring that develops to the surface of the cornea or to distortion that becomes so great that contact lenses can no longer be successfully fitted. (Corneal translplant surgery is an entirely different discussion that I am not going to discuss extensively in this post.) Once the surgery is completed, contact lenses again need to be employed to best allow the patient to achieve good quality vision. If keratoconus contact lens fitting is difficult, post surgical contact lens fitting can be even more so. The good news is that the doctors that help patients with keratoconus contact lens fitting are also experts, in many cases, at fitting lenses to the cornea post surgically. Again, different lenses need to be employed to best correct the vision.
Are there any things that can be done to improve the condition of the cornea as the keratoconus progresses? The answer is yes. Here are some suggestion: Keratoconus has been associated with eye rubbing and eye allergies. Don't rub your eyes!!! It is believed that eye rubbing can help to distort and thin the corneal surface. To help you with not rubbing your eyes you can use eye drops that lessen the symptoms of eye allergies. Some of these are available over the counter and some need to be prescribed. A good over the counter anti-histamine eye drop is "Zaditor". Cool compresses help. There is also some evidence that using cooled tea bags and even cucumber slices help to calm the symptoms of eye itching. Keratoconus can be associated with dry eyes. There are a medications that can help with dry eyes that your doctor can prescribe. There is also a procedure called punctal occlusion that can be done in the doctor's office to help you capture your own tears before they drain from the eyes. Tear quality is very important too. Many patients have poor tear quality as well as keratoconus. Tear quality needs to be improved to make sure that contact lens wear is as comfortable as possible. There is increasing evidence that a new procedure called corneal cross linking can help to strengthen the cornea. In this procedure, the top surface of the cornea is removed and the eye is exposed to specially formulated Ribovlafin (vitamin B2) eye drops. The eye is then exposed to ultraviolet light for a short period of time. This procedure makes the collagen bonds in the cornea stronger and can help to stabilize the condition. The eye is patched with a bandage contact lens for a period of time until the top surface of the cornea can normalize. Once the top surface regrows, the bandage lens can be removed. This procedure is undergoing clinical trials here in the United States. Excellent results have been reported in Europe where the procedure originated. Evidence shows that to be successful the top surface of the cornea must be removed to allow proper penetration of the Riboflavin eye drops. In addition to this treament, it is possible to improve the cornea surface quality, once it no longer will support contact lenses due to irregularity, with the addition of what are known as "Intacts". These are small plastic inserts that are placed into the cornea to make the surface more regular. There have been positive reports from this procedure. This procedure is considered when the eye will no longer accept custom contact lenses due to increasing irregularity. Once the "Intacts" are inserted, contact lenses again need to be fitted to the eye. All of the above discussion regarding fitting of the contact lenses again applies to the refitting after the insertion of the "Intacts".
Here are some of the lenses that are used to fit corneas that have keratoconus: Rose K, Dyna Z Intralimbal, Macrolens, Acuity One, SI02, Soper, Synergeyes KC and Clear Kone and many more. In addition, sometimes "piggyback" contact lenses can be employed. This involves placing a soft contact lens on the eye first and then placing a rigid lens on top of it. This can be successful in many cases. It can be done with what are known as silicone hydrogel soft contact lenses and any variety of rigid lens placed over the soft contact lens. There are aslo available special soft contact lenses that have a small "cut out" in the center to allow the rigid lens to seat itself in the center of the lens and remain stable. Your contact lens fitter probably has some favorites to work with, but it is extremely important to know that it takes many different types of lenses in diagnostic sets at the fitter's office to best asses the proper fit for each patient.
I hope this discussion will be helpful to the keratoconus patient in learning the many different approaches to fitting contact lenses to the keratoconic cornea. If you have any questions, I may be emailed at jon@villageeyes.com.
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