Keratoconus
Keratoconus is a progressive eye disease in which the normally round cornea thins and begins to bulge into a cone-like shape. This cone shape deflects light as it enters the eye on its way to the light-sensitive retina, causing distorted vision. Tiny fibers of protein in the eye called collagen help hold the cornea in place and keep it from bulging. When these fibers become weak, they cannot hold the shape and the cornea becomes progressively more cone shaped.
Keratoconus appears to run in families. If you have it and have children, it’s a good idea to have their eyes checked for it starting at age 10. The condition happens more often in people with certain medical problems, including certain allergic conditions. It’s possible the condition could be related to chronic eye rubbing. Most often, though, there is no eye injury or disease that can explain why the eye starts to change. The exact cause of keratoconus is unknown. There are many theories based on research and its association with other conditions. However, no one theory explains it all and it may be caused by a combination of things. It is believed that genetics, the environment and the endocrine system all play a role in keratoconus. About 7% of patients with keratoconus have known relatives with the disease. Generally speaking, there is about a 1 in 10 chance of a patient with keratoconus having an offspring with the disease (unless there is evidence of keratoconus in successive generations, which increases the probability level). Additionally, there may be links to the endocrine (hormonal) system in that keratoconus tends to appear in its early stages at puberty. Associations with allergy (“atopy”) are common as well.
Keratoconus can cause various kinds of visual distortions. Common symptoms like those pictured are: ghosting, multiple images, glare, halos, starbursts around lights and blurred vision. The earliest signs of keratoconus are usually blurred vision and frequent changes in eye glass prescription, or vision that cannot be corrected with glasses. Symptoms of keratoconus generally begin in late teenage years or early twenties, but can start at any time. Other symptoms include: Increased light sensitivity, Difficultly driving at night, Halo’s and ghosting especially at night, Eye strain, Headaches and general eye pain, Eye irritation, excessive eye rubbing. Keratoconus, especially in the early stages can be difficult to diagnose and all of the above symptoms could be associated with other eye problems. Simply recognizing symptoms does not by itself diagnose keratoconus.
Keratoconus can usually be diagnosed with a slit-lamp examination. The classic signs of keratoconus that the Davis EyeCare will see when examining your eyes include:
Corneal thinning Fleischer’s ring (an iron colored ring surrounding the cone) Vogt’s striae (stress lines caused by corneal thinning) Apical scarring (scarring at the apex of the cone).
Irregular curvature of the cornea measures by our topographer. Corneal topography: a computerized instrument that measures three-dimensional “maps” of the cornea. A typical corneal topography map looks like this:
There is no one design that is best for every type or stage of keratoconus.The needs of each individual is carefully weighed to find the lens that offers the best combination of visual acuity, comfort and corneal health.
Soft Lenses
The role of soft lenses for keratoconus vision correction has changed dramatically in the past year. The new soft lens designs combine the latest technologies in silicone hydrogel materials and complex mathematics to offer comfortable wear and excellent vision. Older soft lenses draped over the irregular keratoconus cornea assuming the same irregular surface as the KC cornea without correcting the visual distortion caused by the irregularly shaped KC cornea.
RGP Contact Lenses
Rigid Gas Permeable (RGP or GP) contact lenses are primary option for correcting KC vision. The rigid lens masks the underlying irregular cornea and functions as the new refractive surface of the eye, with the tear film filling in the space between the back of the contact lens and the front of the eye. “Rigid” defines the type of lens. “Gas Permeable” describes the lens material. There are many different RGP lens designs.
Piggy-backs
This is a two lens system; an RGP lens worn on top of a soft lens. The RGP lens provides crisp vision and the soft lens acts as a cushion providing comfort. The piggy back system not only helps in the fitting of contact lenses on distorted corneas they also aid in the comfort and wearing contact lenses when the cornea becomes very sensitive.
Hybrid lenses
This is a lens design combination that has an RGP center surrounded by a soft peripheral “skirt”. Hybrid contact can provide the crisp optics of a GP lens and wearing comfort of soft contact lenses. They are available in a wide variety of parameters to provide a fit that conforms well to the irregular shape of a keratoconic eye. The Clear Kone has unique geometry of both the rigid center and soft periphery. The result is a lens that vaults the central cornea and aligns with the soft periphery from the peripheral cornea out to the sclera. The lens has excellent centering, movement, and comfort characteristics. Davis EyeCare was involved in the initial pre-market evaluation of this exciting new lens design. Our results have been very positive. We have been able to fit patients with keratoconus who have failed at many other lens designs.
Scleral lenses
These are large diameter lenses that rest on the white part of the eye, called the sclera, and vaults over the cornea. The size can be an alarming prospect for some, but scleral lenses have many advantages. Because of their size, they do not fall out and dust or dirt particles cannot get under them during wear. They are surprisingly comfortable to wear because the edges of the lens rests above and below the eye lid margins so there is no lens awareness. The introduction of rigid gas permeable (RGP) materials has made this design more readily available.
There is no one “best” lens for keratoconus. The “best lens” is the one that fits your eye, corrects your vision, and is comfortable to wear. Rely on an experience of Davis EyeCare to partner with you and select the best treatment for you. We have fit thousands of patients with various lens designs that suit each patient’s lifestyles and corneal anomaly.
Intacs
Intacs is the trademark name for micro-thin prescription inserts which were previously used as a form of refractive surgery in the treatment of low levels of myopia or nearsightedness, but has recently received FDA approval for keratoconus.
Intacs for Keratoconus are thin plastic, semi-circular rings that are surgically placed into the mid layer of the cornea. When inserted in the keratoconus cornea they flatten the cornea, changing the shape and location of the cone. The placement of Intacs remodels and reinforces the cornea, eliminating some or all of the irregularities caused by Keratoconus. This allows for some degree of improvement in vision and in some instances, more stable contact lens fitting. This can also improve uncorrected vision, however, depending on the severity of the KC, glasses or contact lenses may still be needed for functional vision.
Corneal Collagen Crosslinking
Corneal Collagen Crosslinking with Riboflavin (CXL) is a developing keratoconus treatment. CXL works by increasing collagen crosslinks which are the natural “anchors” within the cornea. These anchors are responsible for preventing the cornea from bulging out and becoming steep and irregular. This is a new treatment that increases the stiffness and rigidity of the cornea and stabilizes the cornea from becoming more thin.
During the corneal crosslinking treatment, custom-made riboflavin drops saturate the cornea, which is then activated by ultraviolet light. Riboflavin (vitamin B2) is a naturally occurring compound which strongly absorbs UV light. By applying riboflavin to the cornea at the same time as exposing it to a UV light source, the riboflavin not only enhances the cross-linking effect of the UV light, but also absorbs the light to an extent that the inner layers of the cornea and intra-ocular structures are protected from the potentially damaging effects of the light rays. This process has been shown in laboratory and clinical studies to increase the amount of collagen cross-linking in the cornea and strengthen the cornea. Collagen crosslinking is not a cure for keratoconus. The aim of this treatment is to arrest progression of keratoconus, and thereby prevent further deterioration in vision and the need for corneal transplantation. Glasses or contact lenses will still be needed following the cross-linking treatment (although a change in the prescription may be required) but it is hoped that it could limit further deterioration of vision.
Corneal Transplant
Although only 10-15% of those with keratoconus ultimately progress to require corneal transplant surgery, because contact lenses can no longer correct vision adequately or contact lens intolerance develops. Lens intolerance occurs when the steepened, irregular cornea can no longer be fitted with a contact lens, or the patient cannot tolerate the lens due to the thinness of the corneal tissue. Corneal transplantation is one of the most successful forms of organ transplantation. Rejection of corneal tissue is relatively infrequent and is very successfully managed with topical medication eye drops. The outcome for corneal transplantation in cases of keratoconus is very good. Following corneal transplants, most patients do require glasses and often contact lenses for proper visual correction. Vision varies a great deal after a transplant and continues to change for many months. Davis EyeCare is affiliated with a number of the most highly respected corneal transplant surgeons in the country. Should any of our keratoconus require corneal transplantation, Davis EyeCare will make the most appropriate referral for you.
Keratoconus Diagnosis and Management
Davis EyeCare has been visited by keratoconic patients all over the world for contact lens management. Their experience has allowed thousands of keratoconic patients to achieve clear vision, when less experienced lens fitters had failed. Davis EyeCare receives referrals for the treatment of keratoconic patients from other doctors and universities throughout the United States.
