What Is Keratoconus?

July 11, 2022


Contributing Author: Dr. Reena Gupta, MD

Keratoconus (KC) is an eye disease characterized by progressive thinning and changes in the shape of the cornea. The cornea is the clear, dome-shaped layer at the front of your eye. It helps to focus light into your eye to allow you to see clearly. Tiny fibers of protein in your eye (called collagen) help hold your cornea in place. With keratoconus, these collagen fibers get weak, causing the cornea to thin and bulge into an irregular cone shape. Keratoconus affects around one in every 2,000 people, usually in their late teens or early twenties, and can progress slowly for ten years or more. The condition usually affects both eyes, although one eye may be worse than the other. Keratoconus is the most common reason for corneal transplantation in the United States.

What Causes Keratoconus?

The definitive cause of keratoconus remains unknown, although genetic and environmental factors are thought to be involved. Environmental factors include eye rubbing, atopic disease, sun exposure, and geography. According to the American Academy of Ophthalmology (AAO), about 1 in 10 people with keratoconus have a parent with this condition.

Risk factors for developing keratoconus include:

  • Genetics – A family history of keratoconus can increase your chance of developing the condition. If you have it, get your children’s eyes examined around age 10 for symptoms.
  • Age – This eye disease is frequently detected in adolescence. As the condition advances, young individuals with severe keratoconus are more likely to require surgical intervention.
  • Chronic eye inflammation – Constant inflammation from allergies or irritants can break down the corneal tissue, leading to a higher risk of developing keratoconus.
  • Eye rubbing – Excessive eye rubbing can cause corneal thinning. It can also influence the progression of keratoconus if you already have it.
  • Medical conditions – Studies have found a connection between keratoconus and conditions such as retinitis pigmentosa, Down syndrome, Marfan syndrome, Ehlers-Danlos syndrome, Leber congenital amaurosis, granular corneal dystrophy, osteogenesis imperfecta, and mitral valve prolapse.

Can Keratoconus Damage Vision?

Keratoconus is the most prevalent ectatic corneal disorder. It’s distinguished by a thin cone-shaped cornea that causes myopia, irregular astigmatism, and visual impairment. It affects people of all ethnic origins and genders. Environmental and genetic factors may both play a role in its pathogenesis. Untreated keratoconus can lead to permanent corneal damage or even vision loss. Some cases of this condition may require a corneal transplant if the vision is significantly affected. Patients with keratoconus shouldn’t undergo laser vision correction surgery such as LASIK. The procedure can further weaken the cornea and cause poor vision.

Symptoms of Keratoconus

The signs and symptoms of keratoconus may change as the condition progresses. In the early stages, keratoconus symptoms can include:

  • Slight blurring of vision
  • Increased sensitivity to bright lights and glare
  • Eye redness or swelling

Early stages of the disease are treatable with eyeglasses, but corneal transplantation will be necessary to restore vision in late childhood and early adulthood.

Late-stage symptoms often include:

  • Blurry or distorted vision
  • Sudden worsening or clouding of vision
  • Double vision, when looking with just one eye
  • Frequent prescription changes to your eyeglasses due to increased nearsightedness (myopia) or astigmatism.
  • Not being able to wear contact lenses, as they no longer fit or are uncomfortable.

The progression of this corneal disease typically takes years, but it can escalate quickly for certain individuals. The cornea can abruptly enlarge and become scarred. And when the cornea contains scar tissue, it loses its smoothness and clarity, resulting in even more distorted or blurred vision.

Diagnosis of Keratoconus

Keratoconus can be diagnosed through a routine eye exam. Your ophthalmologist will discuss your medical history and examine your cornea to determine if there is any change to its shape. Your ophthalmologist may also perform the following tests to diagnose the condition:

  • Corneal topography – is the most accurate way to diagnose early keratoconus and track its progression. During a corneal topography, a computerized image is taken that creates a map of the cornea’s curve.
  • Slit-lamp exam – can help detect abnormalities in the cornea’s outer and middle layers.
  • Pachymetry – is used to measure the thinnest areas of the cornea.

It’s important to note that keratoconus may develop before the symptoms appear. Hence, it’s crucial to go for regular and timely checkups to diagnose the condition early on and prevent it from worsening. This is particularly true for children with a genetic predisposition to developing the disorder.

Keratoconus Treatment

Treatment for keratoconus focuses on vision correction depending on the severity of the disease. Treatment for early stages of keratoconus includes glasses or soft contact lenses to treat nearsightedness and astigmatism. However, as the corneal disease progresses and worsens, you may have to be fitted with rigid, gas-permeable contact lenses or other lenses, such as scleral lenses, for better vision.

Treatment options during intermediate and advanced stage keratoconus include:

  • Corneal collagen cross-linking – A vitamin B2 solution is applied to the eye during this one-time in-office treatment. The solution is then activated by ultraviolet light for about 30 minutes or less to cause new collagen bonds to form, recovering and preserving some of the corneal thickness and shape. While collagen cross-linking cannot entirely fix the diseased cornea, it can help keep the vision from worsening and, in some cases, may also improve vision. Cross-linking as a treatment for progressive keratoconus was approved by the U.S. Food and Drug Administration (FDA) in April 2016 after clinical trials showed that it stopped or mildly reversed the bulging of the human cornea within three to 12 months of the procedure.
  • Corneal ring – A regular contact lens may become difficult to use if you have severe keratoconus. Intacs are small implantable, curved devices surgically inserted into your cornea to help flatten its surface, allowing for improved vision and better contact lens fit. Intacs are removable and exchangeable and can be inserted in under 15 minutes.
  • Corneal transplant –. During a corneal transplant for advanced keratoconus, your ophthalmologist may replace all or part of your central cornea with healthy donor cornea tissue. This surgical option is performed in an outpatient setting and takes about an hour to complete. Keratoconus patients will require corrective lenses after the cornea transplant surgery for clearer vision.

Is LASIK Possible With Keratoconus?

Laser eye surgeons will oppose laser vision correction if you have keratoconus, even moderate keratoconus. LASIK and PRK are procedures that reshape the cornea by removing microscopic tissue fragments. However, removing tissue from a cornea that is already fragile due to keratoconus severely weakens the cornea and jeopardizes its integrity.

Although keratoconus cannot be prevented, treatment can help control symptoms and slow the progression of the disease. If you experience any signs or symptoms of mild or moderate keratoconus, schedule an appointment with an ophthalmologist to check your eyes. With early diagnosis and prompt intervention, you may retain good vision and lead an active, normal lifestyle.

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