Keratoconus is a relatively rare degenerative condition which causes structural changes within the cornea (the front of the eye). These changes result in the cornea growing forwards and changing to a more conical shape. (A healthy cornea is more spherical in shape). If you have Keratoconus your vision will be distorted because of the changed shape.
Keratoconus is a serious but treatable condition. If the progression of the change of shape of the cornea is not physically halted it can ultimately lead to the rupture of the cornea resulting in blindness if a corneal graft is not performed and even with a corneal graft eyesight may be severely compromised.
At the Contact Lens Practice we are experts at working with this condition and have been able to achieve vision up to and above that required to read a number plate at 25 yards for many of our patients. In other words some Keratoconic patients come to us legally unable to drive but leave intent on booking driving lessons!
Glasses are not very effective in correcting Keratoconus as it is impossible to create the necessary curves on a spectacle lens that would cause the light to focus correctly at the back of the eye. It may be possible to improve your vision a little but it will still be distorted and since by definition this condition continually changes frequent changes of spectacle lens will be necessary which of course means more expense.
Rigid Contact Lenses on the other hand exert a positive pressure over the top of the cornea so holding it in the required shape for optimal vision. Rigid Oxygen Permeable lenses are those most frequently used to correct Keratoconus. These used to be relatively normally sized lenses which fitted between the eyelids but, over recent years with computer controlled lathes, we have been able to develop new designs. Whilst still Rigid and Oxygen permeable these fit onto the sclera – the white of the eye, like soft lenses. These not only usually give better vision than smaller KC lenses but vastly improved comfort since the sclera is virtually insensitive.
Another new concept is ‘hybrid’ lenses which have a Rigid Oxygen permeable centre attached to a soft peripheral ‘skirt’. These lenses are therefore superbly comfortable and offer excellent visual acuity – they are also available for all the less complex vision errors and can correct astigmatism and be made as varifocals!
If neither of these produce the best results we may recommend a “piggy back” system – a soft lens with a rigid lens on top. If the base soft lens is made from an oxygen permeable enough material this may often be left in overnight so that the wearer only has to apply and remove one pair of lenses most nights.
There is one other alternative which is a Scleral Lens or Haptic. First fitted in the 1880’s and made from glass these fit over the whole of the eye and have always been very comfortable to wear but caused severe problems because they restricted oxygen flow to the cornea. They have now graduated to being made in highly oxygen permeable plastics. Click here for more information about these lenses.
Cross linking therapy is being used for a number of diseases of the cornea and is proving a useful treatment in conjunction with other surgical techniques such as Intacs and refractive laser surgery. However Cross linking is not for everybody, the first requirement is to ensure that the thickness of the cornea is adequate for the treatment. Special non invasive measuring devices are used by your specialist to accurately and quickly take these readings.
For much more go to the Keratoconus Group web site.