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Keratoconus

Keratoconus is a thinning of the corneas leading to warping and distorted vision.

Anatomy image showing Keratoconus

Keratoconus is a progressive eye disease resulting in a thinning and subsequent warping and distortion of the cornea. The normally spherical shape of the cornea is distorted, and a cone-like bulge develops.

The cone shape causes deflection of light as it enters the eye to the retina which causes visual distortion and significant visual impairment. Keratoconus is normally detected in patients in their teens or twenties.

What are the causes of keratoconus?

The exact causes of keratoconus remain unknown, however current research indicates three main contributing factors:

Enzyme imbalance

New research has suggested that weakening of corneal tissue that leads to keratoconus can be attributed to an imbalance of enzymes in the cornea. This imbalance makes the cornea more susceptible to oxidative damage and bulge forward which causes the cornea to weaken.

Genetic origin

Studies indicate about 8% of patients have relatives with this corneal disease.

Eye rubbing

Patients who suffer from allergies such as hay fever or who have poorly fitted contact lenses (which has led to excessive eye rubbing) can affect the strength of the cornea leading to keratoconus.

What are the symptoms of keratoconus?

Blurred and distorted vision is the main symptom of Keratoconus. This may be overcome in the early stages by prescription glasses or contact lenses. Frequent changes to the prescription could indicate a worsening condition of Keratoconus. Eventually, glasses will not be able to correct higher levels of vision distortion.

  • Vision that is blurred and distorted.
  • More rapid changes in your glasses prescriptions than would normally be expected.

What are the treatment options for keratoconus?

Gas permeable contact lenses

These are rigid lenses that sit very tightly to the cornea and alter the irregular shape with a more uniform refracting surface. This tends to improve vision. The drawbacks include less patient comfort and can require frequent visits to the optometrist to fit and change the prescription.

Collagen Cross Linking

Cross linking slows and, in some cases, reverses the progression of corneal weakening and thinning due to keratoconus.

Treatment involves applying riboflavin (vitamin B2) drops to the eye and applying ultraviolet light after the cornea has absorbed the riboflavin over a 30-minute period. The treatment is thought to mimic the natural increase in rigidity of the cornea which occurs with age and natural exposure to ultraviolet light.

Cross linking has shown to increase corneal rigidity and stops progression of keratoconus in over 90% of those who undergo the procedure.

Corneal Rings

Corneal rings are an alternative treatment for keratoconus designed to reduce the need for a full corneal transplantation. The small plastic semicircular inserts (INTACS or Kerarings) are designed to remain permanently in the cornea. They can be removed or replaced if required. The treatment aims to produce a more rounded, even shape, improving the quality of vision.

Corneal transplant

In severe cases of keratoconus, a corneal transplantation may be needed due to scarring, extreme corneal thinning or increased intolerance to contact lenses. This procedure replaces the keratoconic cornea with healthy donor tissue. Patients may still be required to wear optical correction to enhance vision. Corneal transplantation is often followed by laser vision correction to maximise vision quality.