What is keratoconus?

The cornea is the transparent part which covers the eye and through which light enters. A normal cornea is shaped like a perfectly round ball and is made of collagen fibres which give the cornea its structure and firmness.

Keratoconus is a progressive corneal abnormality, specifically affecting these collagen fibres. The cornea gradually becomes thinner and changes shape from convex to pointed (conic).

Progressive thinning of the cornea leads to a bulging eye with irregular astigmatism (oval shaped eye) and increasing myopia (short-sightedness) as a result.
In most cases (80-90%), both eyes are affected, but a difference in severity between both eyes is common (bilateral asymmetric disorder).
Keratoconus usually develops around puberty up to the age of about 45 years and is more common in men than in women.

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What are the symptoms for keratoconus?

Keratoconus is difficult to diagnose because of its slow development. Possible symptoms might be:

  • Distorted and reduced vision, like looking into a warped mirror
  • Sensitivity to light
  • Changes of lens strength in those who wear glasses or contact lenses
  • Itchy eyes
  • Frequent rubbing of the eyes
  • Double vision with one eye covered

What causes Keratoconus

The true cause of keratoconus is unknown. It is possible that this disorder is caused by multiple factors, both hereditary (10%) and environmental.
Other possible causes are:

  • Constant rubbing of the eyes, especially in people who suffer from allergies
  • Physical disorders, e.g. Down’s and Turner syndromes, osteogenesis imperfecta, atopic eczema, connective tissue disease
  • Ophthalmic disorders
  • Refractive surgery

Treatment of Keratoconus

Keratoconus can be initially treated with corrective lenses or (semi) hard contact lenses, but progressive intolerance will probably occur as time goes by. Corneal transplant used to be the treatment of choice for conditions which continued to degenerate; however, this surgery has been associated with a high risk of complication.

Recently, new technology has been implemented which halts the corneal thinning process – Ultraviolet Cross-linking. There is also a procedure which can normalise the shape of the cornea by way of intracorneal ring segments.

Ultraviolet Cross-linking

A characteristic of keratoconus is reduced cross-linking between corneal collagen fibres which ultimately reduce corneal strength.
Ultraviolet Cross-linking is a newly developed technique. The objective of this treatment is to strengthen the collagen structures in the central cornea by forming new connections between collagen fibres. This increases the strength and stability of the cornea and flattens the central, weaker, thinner area. Levels of myopia and astigmatism will decrease as a result. This treatment can not be used to treat advanced keratoconus.

A photosensitive fluid (riboflavin) is administered to the eye. This penetrates into the deeper layers of the cornea. The cornea is then irradiated with ultraviolet-A light, resulting in an increase in the connections between and thickening of the collagen fibres. After treatment these fibres will be three times stronger. This process stabilises after approximately 6 months, during which time the cornea progressively becomes flatter or less pointed and vision is improved. This treatment can prevent keratoconus from developing further during the progressive phase.

While this procedure formerly took more than 1 hour (30 minutes for the eye drops, 30 minutes UV), AVEDRO technology now means that Ultraviolet Cross-linking treatment takes a maximum of 20 minutes for the eye drops and just 4 minutes of UV irradiation. This is mainly due to changes made to the drops and the higher energy value of the UV source.
An additional advantage is that therapy can now be performed via the trans epithelial route, with the absence of post-operative pain.
Refractive abnormalities (myopia, irregular astigmatism) are treated beforehand with lasers (the topography-guided Excimer laser) or afterwards with toric phakic lens implants.
Which situations benefit from UV Cross-linking?

  • Keratoconus prevention
  • Treatment for the progressive form of keratoconus
  • Corneal ectasia (bulging)
  • Corneal instability after radial keratotomy (cutting of the cornea to correct myopia)
  • Chronic corneal oedema (swelling) and resistant corneal ulcer (open sore)
  • For recurrent keratoconus after corneal transplant surgery

Possible risks associated with this procedure are slow wound healing, abnormal wound healing (this risk is lower with AVEDRO technology) and post-operative infections.
When is UV Cross-linking not recommended?
Corneal thickness of < 325 µm, people with epithelial healing disorders, herpes keratitis and during pregnancy.

Intracorneal ring segments (Intacs)


Intracorneal ring segments (corneal implants) can be used when people can not tolerate contact lenses or to postpone corneal transplant surgery. In an ambulatory procedure under local anaesthetic, 1 or 2 semi-circular rings are placed into the outer edges of the cornea. The central, thinner part of the cornea is thereby flattened, significantly reducing myopia and astigmatism. These rings also support the weaker, bulging part of the cornea.
This technique, which has been used for more than 15 years, recently gained momentum once again when the corneal tunnel incision that was previously carried out by surgical blades could be performed with more precision using a laser device (Ziemer). Using the laser, any corneal irregularity is rectified and the quality of life of the patient clearly increases.

Possible complications include ring displacement and post-operative infections; however, these can be quickly treated if detected at an early stage. After the surgical procedure, short-term irritation, light halos and photophobia may be experienced.

Corneal transplantation

When the above treatments are no longer viable, corneal transplant will be considered. If, during the further progression of keratoconus, it is no longer possible to wear contact lenses, a corneal transplant can offer a solution. Approximately 20% of keratoconus patients will eventually reach this stage

For more info, make an appointment with one of our experienced doctors.