Keratoconus is a progressive eye disease in which the cornea thins and bulges into a cone-like shape, losing its roundness. The eventual cone shape deflects light which enters the eye towards the light-sensitive retina. The result is distorted vision.
Keratoconus can occur in one or both eyes. Keratoconus is relatively rare. If it does occur the onset usually begins in the teens or early twenties.
Symptoms of Keratoconus
Keratoconus may be difficult to detect and it typically develops slowly with few cases proceeding rapidly. As the cornea gradually becomes irregular in shape, progressively nearsightedness and irregular astigmatism increase. This creates problems such as distorted and blurry vision. Glare and light sensitivity as well. Keratoconic patients often need prescription changes every time they visit their eye doctor.
Causes of Keratoconus
The weakening of the corneal tissue which leads to keratoconus appears to be from an imbalance of enzymes in the cornea. The enzyme imbalance makes the cornea susceptible to oxidative damage from free radicals, causing weakness and corneal bulge.
Risk factors for this type of oxidative damage and weakening of the cornea include genetic predisposition, which explaining why keratoconus often affects multiple members of the same family. Keratoconus is also connected to ultraviolet (sun) overexposure, excessive eye rubbing, a history of poorly fit contact lenses along with chronic eye irritation.
For mild forms, eyeglasses or soft contact lenses help. As the severity of the disease progresses and the cornea thins and increasingly distorted shape, glasses or soft contacts will no longer provide adequate vision correction.
Treatments for moderate to advanced keratoconus include:
Gas permeable contact lenses. If eyeglasses or soft contact lenses cannot control keratoconus, then gas permeable (GP) contact lenses are usually the effective. Rigid materials enable the GP lenses to dome over the cornea, replacing the irregular shape with a smooth, uniform refracting surface thus improving vision.
There is a comfort cost though because GP contact lenses can be less comfortable to wear compared to soft lenses. Fitting of the contact lenses on keratoconic corneas are also challenging and more time-consuming. Expect frequent office visits for fine-tuning and fitting of the prescription, especially as the keratoconus continues to progress.
Piggybacking lenses. Some practitioners advocate “piggybacking” two different types of contact lenses on the same eye to better fit the gas permeable contact lens over the cone-shaped cornea. Some patients may find this a bit uncomfortable. The GP lens is fitted on top of the soft contact lens which sits on the eye. The approach is thought to increase patient comfort as the soft lens acts as a cushion under the rigid second lens, the GP lens.
Hybrid contact lenses. Hybrid contact lenses are a relatively new design combining highly oxygen-permeable rigid center with a soft peripheral lens “skirt.” Manufacturers claim their hybrid contacts provide crisp optics of GP lenses alongside wear- comfort rivaling soft contact lenses. Hybrid lenses are available in a wide variety of parameters to provide optimal fit which conforms best to the irregular shape of a keratoconic eye.
Scleral and semi-scleral lenses. These are gas permeable contact lenses which have a large diameter allowing the edge of the lenses to rest on the white part of the eye -the sclera. These lenses will also dome over the irregularly shaped cornea, allowing for a most comfortable fit. They will move less during eye blinks. Scleral lenses cover a larger portion of the sclera, whereas semi-scleral lenses cover a smaller white (eye) area.
Intacs. These are tiny plastic inserts which are surgically inserted just underneath the eye surface in the periphery of the cornea helping to reshape the cornea. The result, clearer vision. Intacs may be advised when keratoconus patients no longer can obtain functional vision with contact lenses or eyeglasses.
Studies show that Intacs can improve the spectacle-corrected visual acuity (BSCVA) of a keratoconic eye by an average of two additional lines on a standard eye chart. The implants have the additional advantage of being removable and changeable. The surgical procedure takes 10 minutes. Intacs might delay but will not prevent the required corneal transplant, if keratoconus progresses.
Corneal crosslinking. This procedure, “CXL” for short, strengthens corneal tissue slowing or preventing the bulging of the eye surface. In turn this procedure can reduce the need to undergo a corneal transplant.
There are two types of corneal crosslinking: epithelium-off and epithelium-on. Epithelium-off crosslinking is where the outer portion of the cornea (epithelium) is removed to allow entry of riboflavin, a B vitamin, to the cornea. Once administered, the riboflavin is activated with UV light. With the epithelium-on method (transepithelial crosslinking), the corneal surface is left intact.
Neither procedure is FDA-approved. However, multiple clinical trials are currently underway. Although cross-linking may already be common in some countries — few doctors in the United States will perform the procedure until it is FDA-approved. For that reason, it’s also not covered by insurance. The procedure costs $2,500 per eye, not including the contacts or eye drops.
Corneal transplant. Some people with keratoconus cannot tolerate a rigid contact lens, or they are beyond the point of contact lenses or known therapies providing acceptable vision. The last resort remedy may be a corneal transplant, also called a penetrating keratoplasty (PK or PKP). Note that after successfully completing a cornea transplant, most keratoconic patients will still need glasses or contact lenses for clear vision.
Transcript of the Video above about Keratoconus.
Hi, This is Dr. Cassis and we are going to talk about Keratoconus today and answer some of the common questions that come up. With Keratoconus what happens is that the cornea, which is the outer layer of the eye, has this disease where it progressivly goes forward and thins out like a cone. So i just wanted to show you an example for this patient. This eye is the eye with the Keratoconus and this eye is the normal cornea. So where the color is hot, obviously it works like a topography map, it is going to be really elevated and this eye hear has it a little bit but not as significant. So that causes problems on many levels. First of all vision, so if the pupil is centered here then looking through this cone is going to cause us a lot of aberration, distortion and blurred vision. So for many years what we have done is use gas permeable lenses, like the small hard lenses that we would put on top of the cone and the thought was to sort of recreate a new optical surface and bring better vision. The disadvantage of gas permeable lenses is mainly comfort, because it is a smaller lens, so every time you blink you feel that lens until you develop a lack of sensitivity or lack of awareness of the lens being in the eye. What we have used more recently is whats called a scleral lens and that is probably at this point the best option to correct your Keratoconus. A scleral lens is also a hard lens but it is much bigger lens and lands on the white part of the eye, so there is no awareness of the lens being on the eye and it is extremely comfortable. And that gives the patient great vision because once again it recreates a new optical surface and gets rid of a lot of distortion and a lot of the blurred vision. So like you see with this patient here, the Keratoconus is much more obvious in the right eye than the left eye. But most of the time it is a bilateral disease, meaning people have Keratoconus in both eyes. One eye is usually more severely infected than the other. In my career I would say that its probably half and half the people that only have it or where its very troublesome in one eye, and half of the people have it where its troublesome in both eyes. The other question that comes up is, If I have Keratoconus will my kids have it? So the risk factors for Keratoconus, there are many different factors that can create the Kerataconus, genetics is one of them. Often those patients have a lot of allergies and are eye rubbers, so the thought is, as you rub your eyes a lot you create or change the shape of cornea, and those patients often have severe allergies. And some times it just happens and we are not sure why a patient will be infected with Keratoconus. It does most of the time progress over time. The thought with the contact lenses is they give great vision and great comfort, in some patients it gets to the point where the cornea is so thinned out that it is no longer functional and those patients have to have a corneal transplant. And now there is new treatments to prevent that from happening and the scleral lens are one of them. There is also chromosome cross linking, there is new things, new technology that prevent the transplant from being necessary. So those are the main facts about Keratoconus, if you have any other questions please call the office 757-596-4018