Keratoconus is a relatively common disorder of the cornea of the eye. It results in blurred vision that is difficult to correct, and often requires specialty lenses called sclerals in order to best correct patients' vision. But what causes it? In today’s video I’ll explain the most common causes.
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Your cornea is the clear, dome-shaped window at the front of your eye. It focuses light into your eye. Keratoconus is when the cornea thins out and bulges like a cone. Changing the shape of the cornea brings light rays out of focus. As a result, your vision is blurry and distorted, making daily tasks like reading or driving difficult.
In addition, the visual difficulty from keratoconus is not easily corrected as in other refractive errors.
We don’t know for sure why people develop keratoconus, however there are several causes that play a role.
Genetics are the cause in about 10% of cases. It’s possible that a parent or sibling might have keratoconus as well.
We do know that Eye Rubbing plays a significant role in the pathogenesis of the disease. Interestingly, patients who develop keratoconus tend to rub their eyes differently than other patients. I’ll demonstrate for you how my patients with allergies rub their eyes. The difference is that if you ask a patient with keratoconus how they rub their eyes, it almost always involves very deep rubbing and using a knuckle . In addition, I’ve noticed patients will often sleep on their side with their hands near their eyes, potentially even on their eyes causing pressure all night long. So why does eye rubbing cause keratoconus? It hypothesized that the pressure exerted on the cornea breaks down the collagen bonds of the cornea, resulting in the thinning over time.
Eye Allergies may be a cause, although it seems that might be related to the eye rubbing above. I do put my patients with keratoconus on a prophylactic allergy drop to reduce the stimulus to rub/itch.
Another absolute cause of Keratoconus are Systemic Connective Tissue Diseases
Marfan’s Syndrome and Ehler’s Danlos syndromes are two connective tissue disorders that result in a larger proportion of patients with the disease having keratoconus.
Is Your Blurred Vision a Cornea Disorder or Connective Tissue Disease?
Keratoconus often starts when people are in their late teens to early 20s. The vision symptoms slowly get worse over a period of about 10 to 20 years.
Keratoconus often affects both eyes, and can lead to very different vision between the two eyes. Symptoms can differ in each eye, and they can change over time.
In the early stage, keratoconus symptoms can include:
slightly distorted vision, where straight lines look bent or wavy
increased sensitivity to light and glare
eye redness or swelling
Even in the early stage, these changes in the vision can cause depth perception issues.
In later stages, keratoconus symptoms often include:
more blurry and distorted vision
not being able to wear contact lenses. They may no longer fit properly and they are uncomfortable.
Keratoconus usually takes years to go from early- to late-stage. For some people, though, keratoconus can get worse quickly. The cornea can swell suddenly and start to scar. When the cornea has scar tissue, it loses its smoothness and becomes less clear. As a result, vision grows even more distorted and blurry.
These later stages of keratoconus are considered advanced.
Here's another video about keratoconus. I go over the latest keratoconus treatments in a dedicated video.
That’s it for today’s eye school about keratoconus causes.
Class is dismissed. See you next time!