Keratoconus

What is keratoconus?

Keratoconus is a progressive disease of the cornea. It is the 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 has been found to occur in one of both eyes and is normally detected in patients in their teens or twenties.

Causes:

The causes remain unknown, however 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 is another factor with studies indicating about 8% of patients have relatives with this corneal disease.

Keratoconus is associated with eye rubbing. Patients who suffer from allergies such as hayfever and causes excessive eye rubbing due to symptoms of itchiness and sensitive skin. Other factors can also be poorly fitted contact lenses which may lead to chronic eye irritation.

Signs and symptoms:

Commonly in early stages of keratoconus blurred and distorted vision can be corrected with glasses.

If keratoconus progresses the cornea continues to thin and becomes more irregular.

Other signs can include frequent changes to glasses prescription. This is when glasses and soft contact lenses are often not an option, as they are unable to correct higher levels of astigmatism.

Treatment:

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.

 

Corneal Rings

Corneal Intrastromal rings such as Kerarings and Intacs are an alternative treatment for keratoconus designed to reduce the need for corneal transplantation.

The INTACS or Kerarings inserts are small plastic semicircular inserts and are designed to remain permanently in cornea eye. They can be removed or replaced if required. The treatment aims to produce a more rounded, even shape, improving the quality of vision

The procedure is performed under local anaesthesia. During the procedure channels are made within the cornea and INTACS or Kerarings are inserted into the cornea to alter the shape. A single stitch may be used if required over the incision.

As with any surgical procedure there are potential risks and benefits. This procedure is not designed to let you obtain good vision without the aid of spectacles and contact lenses, although this does occur in some patients. We aim to improve the visual acuity and the clarity or quality of vision, reduce astigmatism and easier fittings of contact lenses.

As with any surgical procedure there are potential risks and benefits. This procedure is not designed to let you obtain good vision without the aid of spectacles and contact lenses, although this does occur in some patients. We aim to improve the visual acuity and the clarity or quality of vision, reduce astigmatism and easier fittings of contact lenses.

 

Collagen Cross Linking (UVX)

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.

 

Topography Guided Laser Vision Correction combined with Collagen Cross Linking (UVX)

Laser vision correction has traditionally not been available for those with keratoconus. When the cornea is precisely mapped by corneal topography, it is possible to perform laser vision correction to improve the shape of the cornea and improve vision. The laser vision correction procedure is combined collagen cross linking to reduce the risk of progression of keratoconus.

This procedure is not the same as performing laser vision correction in the normal eye. The aim is to maximise vision, not cure the condition, and in some circumstances other treatments such as corneal transplantation may be required.

 

Corneal transplant

In severe cases 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.