Keratoconus

Keratoconus

Keratoconus is characterized by the thinning of the cornea and irregularities of the cornea’s surface. The cornea is the clear, outer layer at the front of your eye. The middle layer is the thickest part of the cornea, mostly made up of water and a protein called collagen. Collagen makes the cornea strong and flexible, and helps keep its regular, round shape. This healthy cornea focuses light so you can see clearly. With keratoconus, the cornea thins and bulges into an irregular cone shape, resulting in vision loss.

Keratoconus generally begins at puberty and progresses into the mid-30s. There is no way to predict how quickly the disease will progress, or if it will progress at all. Keratoconus typically affects both eyes, with one being more severely affected than the other.

Causes

Several things may have a link to the condition:

Family history: If someone in your family has this condition, you have a greater chance of getting it yourself. If you have it, get your children’s eyes checked for signs starting around age 10.

Age: It usually starts when you’re a teenager. But it might show up earlier in childhood or not until you’re 30. It can also affect people 40 and older, but that’s less common.

Certain disorders: Studies have found a connection between keratoconus and systemic conditions such as Down syndrome, Ehlers-Danlos syndrome, osteogenesis imperfecta, and retinitis pigmentosa.

Inflammation: Inflammation from things like allergies, asthma, or atopic eye disease can break down the tissue of the cornea.

Eye rubbing: Rubbing your eyes hard over time can break down the cornea. It can also make keratoconus progress faster if you already have it.

Race: One study of more than 16,000 people with keratoconus found that people who are Black or Latino are roughly 50% more likely to get it than people who are white.

Symptoms 

Symptoms of keratoconus may change as the disease progresses and include:

• Blurry or distorted vision
• Increased sensitivity to light and glare
• Problems with night driving, with streaks or haloes around bright lights
• Frequent changes in glasses prescription

Diagnosis

To diagnose keratoconus, your eye doctor (ophthalmologist or optometrist) will review your medical and family history and conduct an eye exam. He or she may conduct other tests to determine more details regarding the shape of your cornea. Tests to diagnose keratoconus include:

Eye refraction: In this test your eye doctor uses special equipment that measures your eyes to check for vision problems. He or she may ask you to look through a device that contains wheels of different lenses (phoropter) to help judge which combination gives you the sharpest vision. Some doctors may use a hand-held instrument (retinoscope) to evaluate your eyes.

Slit-lamp examination: In this test your doctor directs a vertical beam of light on the surface of your eye and uses a low-powered microscope to view your eye. He or she evaluates the shape of your cornea and looks for other potential problems in your eye.

Keratometry: In this test your eye doctor focuses a circle of light on your cornea and measures the reflection to determine the basic shape of your cornea.

Computerized corneal mapping: Special photographic tests, such as corneal tomography and corneal topography, record images to create a detailed shape map of your cornea. Corneal tomography can also measure the thickness of your cornea. Corneal tomography can often detect early signs of keratoconus before the disease is visible by slit-lamp examination.