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Keratoconus is a progressive eye disease that affects the cornea (the front of the eye). The normally round shaped cornea becomes thin and begins to bulge into a cone-like shape. When this happens, light no longer reaches the retina clearly. Rather, it is distorted, and causes distorted vision. Keratoconus can occur in either one eye or in both eyes. It often begins during a person's teens or early 20's.
Keratoconus can be difficult to detect. As the cornea becomes more irregular in shape, it causes the individual to become more and more nearsighted. Nearsighted means that someone can see at near, and will see blurry at distance. Other symptoms include sensitive to glare and light. Eyeglass prescriptions change rapidly. The diagnosis of Keratoconus is commonly missed if the practitioner is unfamiliar with the early-stage symptoms of the disease.
Early symptoms of Keratoconus include frequent changes in eyeglass prescription as the individual becomes more nearsighted and has greater astigmatism (irregular curvature between the vertical [up and down] and horizontal [side to side]. It can also cause someone to be more sensitive to glare and to light
Corneal Topography is test using a special test instrument that measures thousands of different points on the cornea and enables the doctor to see the precise shape of the cornea. A land topography map tells us about land elevations and depressions; essentially hills and valleys. The corneal topographer, an instrument that we have in our office, enables us to get a "map" of your cornea and enables us make a contact lens to the precise shape of the cornea.
In the mildest form of Keratoconus, eyeglasses or soft contact lenses may help. As the disease worsens, the cornea thins and becomes increasingly more irregular in shape. Glasses and soft contacts may no longer provide adequate vision correction. The preferred treatment for moderate and advanced Keratoconus is Gas Permeable contact lenses. GP lenses are made of a rigid lens material which enables the lenses to vault over the cornea, replacing its irregular shape with a smooth, uniform refracting surface to improve vision.
Prescribing contact lenses on a keratoconic cornea is challenging and time-consuming. You can expect frequent return visits to fine-tune the fit and the prescription, especially if the Keratoconus continues to progress.
Special hybrid lenses by SynergEyes, called ClearKone, combine the benefit of a highly oxygen-permeable rigid center with a soft peripheral "skirt." ClearKone was designed specifically for Keratoconus and vaults above the eye's cone shape for increased comfort. The center part provides the crisp optics of a GP lens and outer soft skirt offers the benefit of comfort typically associated with soft contact lenses. They are available in a wide variety of parameters customized to provide a fit that conforms well to the irregular shape of a keratoconic eye.
Scleral and Semi-Scleral lenses are larger diameter lenses (about the size of a normal soft contact lens) made in gas permeable (GP) materials and are designed to rest on the white part of the eye (sclera). Scleral lenses cover a larger portion of the sclera, whereas semi-scleral lenses cover a smaller area. They vault over the irregularly shaped cornea and they feel more comfortable than prior designs. The Boston Scleral Lens Prosthetic Device (BSLPD) is a scleral lens that has been given a proprietary name.
Custom lenses prescribed in our office have resulted in very positive outcomes. They are done close to home and usually at considerably less cost.
People with severe dry eye also find relief when using scleral lenses.
More drastic treatments of Keratoconus include:
- Intacs - these are special plastic inserts surgically implanted into the cornea just below the eye's surface to re-shape the cornea for clearer vision. Intacs can improve vision, and can be removed or exchanged. Intacs may delay but cannot prevent a corneal transplant if Keratoconus continues to progress.
- Corneal cross-linking is a non-invasive procedure that strengthens corneal tissue in an attempt to halt bulging of the eye's surface in Keratoconus. Corneal cross-linking also is being investigated as a way to treat or prevent keratoconus-like complications following LASIKor other vision correction surgery.
- Corneal transplant is sometimes needed if contact lenses are not tolerated and is a last resort. Another term for a cornea transplant is penetrating keratoplasty (PK or PKP). Even after a transplant, eyeglasses or contact lenses are needed for clear vision. Often, after Corneal Transplant, special lenses are needed to restore sight.
Often the causes of Keratoconus are less important than the treatment. Research suggests that the bonds that hold the corneal tissue together are lost because of an imbalance of enzymes within the cornea. This causes the cornea to bulge forward. Risk factors include: a history of family members with Keratoconus, excessive eye rubbing, overexposure to ultraviolet rays from the sun, a history of poorly fitted contact lenses and chronic eye irritation.
