Keratoconus is the gradual thinning and outward bulging of the cornea into a cone shape. This progressive eye condition usually affects both eyes by thinning the corneas from that of a normal rounded dome-shape into one that has a cone-shaped bulge. The cornea is the clear, central part of the surface of the eye. In those patients with keratoconus, the cone-shaped cornea deflects light and causes distorted vision.
Causes of Keratoconus
Although many theories have been proposed, there is no definitive cause of keratoconus. Possible causes include:
- Genetics
- A collagen deficiency
- Overexposure to ultraviolet rays from the sun
- Excessive eye-rubbing
- Allergies
- An injury to the eye
- Diseases of the eye
Symptoms of Keratoconus
Keratoconus often begins to develop in the teen years to the early 20s, although it can develop at any age. Changes in the shape of the cornea occur gradually, usually over several years. In most patients with keratoconus, both eyes eventually become affected.
Keratoconus can be difficult to detect because it usually develops very slowly. Signs and symptoms of keratoconus may include:
- Distorted and blurry vision
- Increased nearsightedness, or myopia
- Astigmatism
- Double vision
- Halos around bright lights
- Frequent changes in eyeglass prescription
- Inability to wear contact lenses
- Headaches due to eye strain
- Glare
- Light sensitivity
Diagnosis of Keratoconus
After a thorough examination of the eyes, the doctor will measure the curvature of your cornea to determine whether these symptoms are a result of keratoconus. Some of the tests that will be conducted may include:
- Keratometry
- Corneal mapping or topography
- Measurement of vision
Treatment for Keratoconus
In the early stages of keratoconus, glasses or soft contact lenses may help to correct the nearsightedness and associated astigmatism. As the condition progresses and the cornea becomes thinner, more advanced treatment is required.
Rigid Gas Permeable (RGP) Contact Lenses
If eyeglasses or regular soft contact lenses cannot control keratoconus, rigid gas-permeable contact lenses are usually the preferred treatment. The rigid lens covers the cornea, replacing the cornea's irregular shape with a smooth, uniform refracting surface, improving vision. RGP lenses can be less comfortable to wear than soft lenses and fitting contact lenses on a cornea with keratoconus can be a challenge. Frequent doctor visits may be necessary to fine-tune the fit and prescription of RGP lenses, especially if keratoconus continues to progress.
Intacs® Corneal Implants
Intacs are small implantable rings inserted into the mid-layer of the cornea to flatten it, changing the shape and location of the cone. Intacs may be needed when the distorted vision from keratoconus can no longer be corrected with contact lenses or eyeglasses. The implants are able to be removed and exchanged as needed. Intacs can only delay the need for a corneal transplant, not prevent it, if the keratoconus continues to progress.
Collagen Cross-Linking
Collagen cross-linking is a relatively new method for treating keratoconus. It works by strengthening the corneal tissue to stop it from bulging. In this procedure, eye drops containing riboflavin (vitamin B2) are applied to the cornea and then activated by ultraviolet light. This strengthens the collagen fibers within the cornea.
Corneal Transplant Surgery
A corneal transplant may be recommended for patients with advanced keratoconus, when other treatment methods fail to provide clear vision. This occurs in 10-20% of patients with keratoconus. In corneal transplant surgery, the diseased cornea is removed and replaced with a donor cornea. Healing can take up to a year with a low rate of rejection.
Frequently Asked Questions (FAQ) – Keratoconus
1. What is keratoconus?
Keratoconus is a progressive eye condition in which the cornea, the clear, dome-shaped surface at the front of the eye, thins and bulges into a cone-like shape. This distortion can cause vision problems, as the irregular shape interferes with the way light is focused on the retina, leading to blurry or distorted vision.
2. What causes keratoconus?
The exact cause of keratoconus is not fully understood, but it is believed to be influenced by both genetic and environmental factors. Some potential causes and risk factors include:
- Genetics: Family history of keratoconus increases the risk. It's often seen in individuals with relatives who have the condition.
- Rubbing the eyes: Chronic or excessive eye rubbing may contribute to the development of keratoconus.
- Allergic conditions: Conditions like hay fever and asthma are sometimes associated with keratoconus, possibly due to eye rubbing or inflammation.
- Other conditions: Keratoconus is more common in individuals with conditions such as Down syndrome, Ehlers-Danlos syndrome, and Marfan syndrome.
3. What are the symptoms of keratoconus?
The symptoms of keratoconus typically begin in the teenage years or early 20s and progress gradually. Common symptoms include:
- Blurry or distorted vision, which may worsen over time
- Increased sensitivity to light (photophobia)
- Frequent changes in prescription glasses or contact lenses
- Double vision
- Halos or glare around lights, particularly at night
- Eye irritation or redness due to associated allergies or rubbing
4. How is keratoconus diagnosed?
Keratoconus is diagnosed through a thorough eye exam, which may include:
- Visual acuity test: To assess the clarity of your vision.
- Slit-lamp examination: To examine the cornea and look for signs of thinning or bulging.
- Corneal topography: A specialized imaging test that maps the shape of the cornea, showing any irregularities or conical shape.
- Pachymetry: A test to measure the thickness of the cornea.
5. Can keratoconus be treated?
While there is no cure for keratoconus, various treatments can help manage the condition and improve vision:
- Glasses and contact lenses: In the early stages, vision can often be corrected with glasses or soft contact lenses. As the condition progresses, rigid gas permeable (RGP) contact lenses may be required to correct vision.
- Collagen cross-linking (CXL): A procedure that strengthens the cornea by applying riboflavin (vitamin B2) and exposing it to ultraviolet (UV) light. This helps to stabilize the cornea and slow the progression of keratoconus.
- Intacs: Small, curved inserts placed in the cornea to flatten the conical shape and improve vision. This option is typically used when contact lenses alone are not sufficient.
- Corneal transplant: In advanced cases where vision cannot be corrected with glasses, contact lenses, or other treatments, a corneal transplant (keratoplasty) may be necessary to replace the damaged cornea with a donor cornea.
6. Can keratoconus be prevented?
There is no known way to prevent keratoconus, but there are steps that may help reduce the risk of progression:
- Avoid eye rubbing: Chronic eye rubbing can worsen keratoconus by putting pressure on the cornea. It's important to avoid rubbing the eyes, especially in individuals with a family history of the condition.
- Seek early treatment: Regular eye exams, especially if there is a family history of keratoconus, can help catch the condition early and prevent it from progressing to a more severe stage.
