Keratoconus

What is Keratoconus?

Keratoconus occurs when cornea the clear, dome-shaped front surface of your eye thins and gradually bulges outward into a cone shape.  Keratoconus usually affects both eyes and generally begins to first affect people ages 10 to 25. The condition is non inflammatory and progressive.

 What are the symptoms?

• Blurred or distorted vision
• Increased sensitivity to bright light and glare, which can cause problems with night driving
• A need for frequent changes in eyeglass prescriptions
• Sudden worsening or clouding of vision

How does Keratoconus affect vision?

Vision becomes blurred in Keratoconus because the cornea is not smooth and round. This affects the focus of eye causing short sight (myopia) and astigmatism, in which the light that passes through the eye forms an unclear image at the back of the eye. In advanced stages of keratoconus, some patients may develop scarring in the cornea, which can make their sight blurred by reducing the amount of light which can enter the eye. A small number of patients may experience a sudden, painful loss of vision if fluid from the eye enters a very thin cornea. This is called hydrops and will settle with time.

What are the causes of Keratoconus?

Exact causes of keratoconus are not known, although genetic and environmental factors are thought to be involved. Few factors can increase chances of developing keratoconus:

• Having a family history of keratoconus
• Rubbing your eyes vigorously
• Having certain conditions, such as retinitis pigmentosa, Down syndrome, Ehlers-Danlos syndrome, hay fever and asthma

How is Keratoconus diagnosed?

 Tests to diagnose keratoconus include:

• Eye refraction. In this test, ophthalmologist uses special equipment that measures your eyes to check for vision problems.  Some doctors may use a handheld 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 optical coherence tomography and corneal topography, record images of your cornea to create a detailed shape map of your cornea's surface. The tests can also measure the thickness of your cornea.

What are the treatment options available?

A treatment for keratoconus depends on the severity of condition and how quickly the condition is progressing. Mild to moderate keratoconus can be treated with eyeglasses or contact lenses.Contact lenses do not make keratoconus worse or better, they just improve your vision while you are wearing them.For many people, the cornea will become stable after a few years. Whereas in  some people with keratoconus, the cornea becomes scarred or wearing contact lenses becomes difficult. In these cases, surgery might be necessary.

Lenses

• Eyeglasses or soft contact lenses. Glasses or soft contact lenses can correct blurry or distorted vision in early keratoconus. But people frequently need to change their prescription for eyeglasses or contacts as the shape of their corneas change.
• Hard contact lenses. Hard (rigid, gas permeable) contact lenses are often the next step in treating progressing keratoconus. Hard lenses may feel uncomfortable at first, but many people adjust to wearing them and they can provide excellent vision. This type of lens can be made to fit your corneas.
• Mini Scleral lenses. These lenses are useful for very irregular shape changes in your cornea in advanced keratoconus. Instead of resting on the cornea like traditional contact lenses do, scleral lenses sit on the white part of the eye (sclera) and vault over the cornea without touching it.
  

Therapies

• Corneal cross-linking(CXL) In this procedure, the cornea is saturated with vitamin B2 (riboflavin) drops and treated with ultraviolet light .Used together, they cause fibers within the cornea to cross-link – or bond more tightly and hence cornea stiffens. This treatment mimics the normal age-related stiffening of the cornea, which is known as natural cross-                       The treatment is usually recommended only for patients whose corneal shape scans show that their keratoconus is getting worse. Cross-linking may help to reduce the risk of progressive vision loss by stabilizing the cornea early in the disease.CXL treatment is successful in more than 90% of cases. After treatment, patient will still need to wear spectacles or contact lenses. Eye will be sore for a few days after the procedure. Although vision is often hazy at first, most patients can return to work after one week.
  

Surgery

You may need surgery if you have corneal scarring, extreme thinning of your cornea, poor vision with the strongest prescription lenses or an inability to wear any type of contact lenses. Several surgeries are available, depending on the location of the bulging cone and the severity of your condition. Surgical options include:

• Corneal inserts. During this surgery, tiny, clear, crescent-shaped plastic inserts (intracorneal ring segments) are placed into cornea to flatten the cone, support the cornea's shape and improve vision.
  Corneal inserts can restore a more normal corneal shape, slow progression of keratoconus and reduce the need for a corneal transplant. This surgery may also make it easier to fit and tolerate contact lenses. The corneal inserts can be removed, so the procedure can be considered a temporary measure.
• Corneal transplant. In cases of corneal scarring or extreme thinning,  a corneal transplant (keratoplasty) is needed.
  Penetrating keratoplasty is a full-corneal transplant. In this procedure,  a full-thickness portion of your central cornea is removed and replaced with donor tissue.
  A deep anterior lamellar keratoplasty (DALK) preserves the inside lining of the cornea (endothelium). It helps avoid the rejection of this critical inside lining that can occur with a full-thickness transplant.