Everything You Need to Know About Keratoconus
The eye is a complex organ made up of several layers. The first is the conjunctiva which covers the sclera, also known as the white of the eye. The next is the cornea, a clear dome-shaped layer of tissue that covers the iris and pupil. Its main function is to help focus light into the lens and pupil.
Keratoconus is a progressive condition characterized by a thinning of the cornea that causes it to lose its symmetrical dome shape. Lopsidedness of the cornea can lead to blurry or distorted vision.
What is keratoconus?
Keratoconus is an eye disorder characterized by the transformation of the cornea from a symmetrical dome to an asymmetric or lopsided cone. The primary function of your cornea is to refract light into your pupil. When light passes through your asymmetrical cornea, it can lead to distortion and blurriness in your vision. Symptoms may start in one eye, but in most cases affects both eyes.
What are the symptoms of keratoconus?
The main sign of keratoconus is a thinning of your cornea that disrupts its natural dome shape. In the early stages of keratoconus, it’s common to not have any symptoms. As the condition progresses, asymmetry of your cornea can lead to blurred vision and mild to significant distortion of your vision.
Some of the early signs of keratoconus include:
- Rizzuti sign. A steeply curved reflection seen by shining a light on the side of your cornea closest to your temple.
- Fleischer ring. A brown ring of iron deposit around your cornea that’s most visible with a cobalt blue filter.
- Vogt’s striae. Vertical lines observed on your cornea that usually disappear when a firm pressure is applied over your eye.
You may also experience:
- corneal swelling
- light sensitivity
- halos in your vision
- eye strain
- a persistent desire to rub your eyes
- poor night vision
- nearsightedness (difficulty seeing far away)
- irregular astigmatism (irregular curvature of the eye)
What causes keratoconus?
Researchers still don’t fully understand why some people develop keratoconus. In most cases, it develops for no apparent reason. It’s generally thought that both environmental and genetic factors play a role in its development.
- Family history. It’s thought that some people with keratoconus may carry genes that make them predisposed to its development if they’re exposed to certain environmental factors.
- Underlying disorders. Keratoconus sometimes occurs in the presence of certain underlying disorders, but a direct cause and effect hasn’t been established. These disorders include Down syndrome, sleep apnea, asthma, some connective tissue disorders including Marfan syndrome and brittle cornea syndrome, and Leber congenital amaurosis.
- Environmental risk factors. Some environmental risk factors may contribute to the development of keratoconus including excessive eye rubbing and wearing contacts.
How is keratoconus diagnosed?
To make a keratoconus diagnosis, your eye doctor with give you a thorough eye exam and examine your medical and family history.
During the eye exam, your eye doctor may examine:
- the overall appearance of your eyes
- your visual acuity
- your visual field
- your eye movements
You may also undergo a slit lamp exam where your doctor examines your eye with a special light under high magnification. Diagnosis of keratoconus may also involve a specific imaging test called corneal topography to allow your doctor to examine changes to your eye that aren’t otherwise visible. Corneal topography creates a three-dimensional image of the surface of your cornea.
What is the treatment for keratoconus?
Treatment of keratoconus focuses on maintaining your visual acuity and stopping changes to the shape of your cornea. Treatment options vary based on the severity of the condition and how fast it’s progressing.
Prescription contacts or glasses
Prescription glasses or soft contact lenses can be used to improve visual acuity in mild cases of keratoconus. Due to progressive changes to your cornea, you may require frequent prescription changes.
Some people with keratoconus don’t tolerate contact lenses well due to discomfort, severe corneal thinning, or scarring. If your vision can’t be corrected with lenses, you may require corneal transplant or keratoplasty. This surgery involves replacing your corneal tissue with tissue from a donor. It’s usually only used in severe cases.
Corneal cross-linking device (CXL)
Corneal cross-linking (CXL) is a treatment for patients with keratoconus or post-LASIK ectasia (bulging of the cornea after LASIK surgery). It is successful in over 90% of cases and can prevent their condition from getting worse. Although approved and used in Europe since 2003, it was not FDA approved in the US until April 2016.
What are the risk factors for developing keratoconus?
Risk factors for developing keratoconus include:
- Family history. About 10 to 20 percent of people with keratoconus have a family history.
- Childhood eye-rubbing. Excessive childhood eye rubbing is thought to increase your risk by 25 times.
- Close genetics relation between parents. Having a close genetic relationship between parents is thought to increase your risk of developing keratoconus by about 3 times.
- Race. Studies suggest that keratoconus rates are higher in people who are Asian compared to people who are Caucasian.
- Atopy. It’s been suggested that atopy may be associated with the development of keratoconus, possibly due to increased eye rubbing due to eye irritation. Atopy is the genetic tendency to develop allergic diseases such as eczema, asthma, or allergic rhinitis.