It goes without saying that health and vision go hand in hand. But, it may be surprising for some to learn that eye allergies in children may leave them at risk for a certain eye disease, called keratoconus, which can result in severe and permanent vision impairment. This is important for parents of kids who suffer from eye allergies (and rub their eyes) to know and take appropriate steps to reduce risks for keratoconus. Before I get into that, it's important to establish a little background knowledge.
Millions of Americans live with some sort of vision impairment. Nearsightedness, farsightedness and astigmatism are all considered common refractive errors that occur as a result of natural irregularities in the shape of the eye. The curvature of the front surface of the eye, called the cornea, is essential for vision because it is responsible for about 70% of the eye’s focusing power. When light rays hit the cornea, they are focused onto the lens and then onto the back of the eye, allowing us to see clearly. Astigmatism occurs in about 1 in 3 individuals and can be thought of as the cornea being shaped like a football rather than a perfectly round basketball. Most of the time, astigmatism can be corrected with glasses or contact lenses, just like farsightedness and nearsightedness can be.
Compare the shape of the normal cornea on the left with the cornea in keratoconus on the right.
Vision impairment can also be a result of certain diseases including a progressive condition known as keratoconus. The cornea, a normally dome-shaped structure, is composed of collagen fibers. Keratoconus develops when the collagen fibers in the cornea deteriorate, causing it to become thin and bulge outward, mimicking a cone-shape. This cone-shape causes large, irregular amounts of astigmatism which alters the way light comes into the eye leading to poor vision.
Keratoconus is a relatively rare condition that occurs in about 1 in every 2,000 individuals and it is typically diagnosed in early adulthood. The most common symptom experienced is blurry or distorted vision and this is usually first noticed during late teen years. Other symptoms include halos or glare at night and sensitivity to light. Keratoconus can progress until the third or fourth decade of life before stabilizing and vision during this time can become progressively worse.
Keratoconus is considered at least partly a hereditary disease although some studies show behavioral factors can increase the risk of its development. Eye rubbing, often associated with seasonal allergies, is considered one of the most common and controllable environmental triggers. A very large, 10 year study was recently published and indicated that ocular allergies in children increased their risk 37% for keratoconus. That's a really important fact for parents to know and address. Studies show that the mechanical force of eye rubbing can, over time, reduce the capacity of the cornea to maintain its structure. When someone with a genetic predilection for keratoconus experiences an environmental trigger, such as eye rubbing, it may set the disease into progression. If you or your child experience red, itchy eyes during allergy season, we encourage you to see us to start a treatment plan and minimize symptoms. If we can minimize symptoms and resulting behaviors (eye rubbing), we can hopefully decrease these risks.
There is no cure for keratoconus, however there are treatment options to improve vision. In mild cases, vision can often be corrected with glasses or soft contact lenses. For more advanced cases, specialty rigid lenses can be used to improve vision. Scleral contact lenses in particular, are large contacts that rest on the white part of the eye, called the sclera, and creates a tear filled “vault” over the cornea. In doing so, scleral lenses functionally replace the irregular cornea with a perfectly smooth optical surface, therefore, improving vision. Our own Dr. Scott Nilsson is highly experienced in fitting all of the newest specialty lenses for keratoconus.
In conclusion, we highly recommend parents speak to us about their child's history of allergies. Working together, we can hopefully reduce the risks for keratoconus in allergy suffering children.
Dr. Becky Zaydel