Keratoconus

  • Keratoconus is a progressive 
    eye disease in which the normally round cornea thins and begins to bulge into a cone-like shape. This cone shape deflects light as it enters the eye on its way to the light-sensitive retina, causing distorted vision.

  • Keratoconus can occur in one or both eyes and often begins during a person's teens or
    early 20s.

Keratoconus Signs and Symptoms:

  • As the cornea becomes more irregular in shape, it causes progressive nearsightedness and irregular astigmatism to develop, creatingadditional problems with distorted and blurred vision.  Glare and light sensitivity also may occur.
     

  • Keratoconus patients experience changes in their eyeglass prescription throughout the year and may change every four to six months if the keratoconus is progressive causing the vision to be unstable.
     

 

 

What causes Keratoconus?
 

  • A weakening of the corneal tissue that leads to keratoconus
    may be due to an imbalance of enzymes within the cornea.
    The imbalance makes the cornea more susceptible
    to oxidative damage from compounds called free radicals,
    causing the cornea to weaken and bulge forward.

     

  • Keratoconus risk factors for oxidative damage and
    weakening of the cornea include:


​Keratoconus treatment:
 

In early stages of keratoconus,  eyeglasses or soft contact lenses may help. However, as the disease progresses and the cornea thins and becomes increasingly more irregular in shape,
glasses and regular soft contact lens designs no longer provide adequate vision correction.

 

Treatments for progressive keratoconus include:
 

  1. Corneal Cross-linking:

    • A procedure, also called corneal Collagen Cross-linking or CXL, strengthens corneal tissue to halt bulging of the eye's surface in keratoconus.  
       

    • The aim of Corneal Cross-linking is to strengthen the cornea by increasing the number of "anchors" that bond collagen fibers together.










       

    • There are two versions of Corneal Crosslinking:
       

      • Epithelium-off Cross-linking,

        • Outer layer of the cornea (epithelium) is removed to allow entry
          of riboflavin, a type of B vitamin, into the cornea, which then is activated with UV light.

           

      • Epithelium-on method (also called transepithelial crosslinking),

        • Epithelium is left intact during the treatment.

        • Advantages include less risk of infection, less discomfort and faster visual recovery.  
           

    • Corneal crosslinking may reduce significantly the need for corneal transplants among keratoconus patients.  
       

    • Corneal crosslinking may also is being investigated as a way to treat or prevent complications following LASIK or other vision correction surgery.  
       

    • Using a combination of Corneal Cross-linking and INTACS implants also has demonstrated promising results for treating keratoconus. 
       

    • Also, progressive mild to moderate keratoconus has been safely and successfully treated with a combination of corneal crosslinking and implantation of an Astigamtism Intraocular Lens Implant or toric phakic IOL.
       

  2. Custom Soft Contact Lenses
     

    • ​Custom soft contact lenses specially designed to correct mild-to-moderate keratoconus.
       

    • These lenses are made-to-order based on detailed measurements of the person's keratoconic eye(s) and may be more comfortable than gas permeable lenses (GPs) or hybrid contact lenses for some wearers.  
       

    • These lenses have a very wide range of fitting parameters for a customized fit and are larger in diameter than regular soft lenses for greater stability on patients with keratoconus.
       

  3. Gas permeable Contact Lenses

    • When eyeglasses and soft contact lenses often cannot provide adequate visual acuity in cases of more severe keratoconus, Gas Permeable (GP) contact lenses usually are the preferred treatment.
       

    • GP lenses vault over the cornea, replacing its irregular shape with a smooth, uniform refracting surface to improve vision.  
       

    • Fitting contact lenses on an eye with keratoconus often is challenging and and take time to fit, where one can expect frequent return visits to your eye care provider to carefully fit and the prescription, especially if the keratoconus continues to progress.














       

  4. "Piggybacking" Contact Lenses

    • Fitting a gas permeable contact lens over a cone-shaped cornea can sometimes be uncomfortable for a person with keratoconus, therefore the idea of "piggybacking" two different types of contact lenses on the same eye.

       

    • For keratoconus, this method involves placing a soft contact lens, such as one made of silicone hydrogel, over the eye and then fitting a GP lens over the soft lens.
       

    • This approach increases wearer comfort because the soft lens acts like a cushioning pad under the rigid GP lens. 
       

  5. Hybrid Contact Lenses

    • Combines a highly oxygen-permeable rigid center with a soft peripheral "skirt."
       

    • These lenses were designed specifically for keratoconus, and the central GP zone of the lens vaults over the cone-shaped cornea for increased comfort.  
       

    • Hybrid contact lenses provide the crisp optics of a gas permeable contact lens and wearing comfort similar to soft contact lenses.
       

    • Lens designs available in a wide variety of parameters to provide a fit that conforms well to the irregular shape of a keratoconic eye.
       

  6. Scleral and Semi-scleral Lenses

    • These are large-diameter gas permeable contacts — large enough that the periphery and edge of the lens rest on the "white" of the eye (sclera).  
       

    • Scleral lenses cover a larger portion of the sclera, whereas semi-scleral lenses cover a smaller area. 
       

    • The center of scleral and semi-scleral lenses vaults over the irregularly shaped cornea, these lenses don't apply pressure to theeye's cone-shaped surface for a more comfortable fit.  
       

    • These larger lenses also are more stable thanconventional gas permeable contact lenses, whichmove with each blink because they cover only a portion of the cornea.
       

  7. INTACS:  Intrastromal Corneal Ring Segments

    • INTACS are FDA-approved clear, arc-shaped corneal inserts that are surgically positioned within the peripheral cornea
      to reshape the front surface of the eye
      for clearer vision.
       

       

    • INTACS may be needed when keratoconus
      patients no longer can obtain functional vision
      with contact lenses or eyeglasses.
       

       

    • Several studies show that INTACS can improve
      the best spectacle-corrected visual acuity of a
      keratoconic eye by an average of two lines
      on a standard eye chart.

       

    • The implants also have the advantage of being
      removable and exchangeable.  INTACS might delay
      but not necessarily prevent a corneal transplant
      if keratoconus continues to progress.

       

  8. Corneal Transplant

    • ​Some patients with keratoconus do not tolerate a rigid contact lens, or the steepness of the corneas is too great that conventional contact lenses or other therapies no longer provide acceptable vision.  
       

    • The last remedy to be considered may be a cornea transplant, also called a penetrating keratoplasty (PK or PKP).
       

    • Most often after  transplant stabilizes, glasses or contact lenses are needed for clear vision.
       

Make an appointment for an eye exam with Dr. Nanda at the Nanda Dry Eye and Vision Institute at 832-966-0660  if you notice any changes in your vision.

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