Keratoconus
Keratoconus is a condition that affects the cornea of the eye. The cornea is at the front of the eye and it is performs a lot of the focussing of the eye. The cornea is made up of several layers, the middle and thickest layer called the stroma.
The layers of the cornea. In keratoconus the stroma is affected
In keratoconus – which literally means “cornea like a cone” the stroma thins leading to a loss in structural integrity of the cornea. This causes the cornea to bend over time into a cone shape.
In keratoconus the cornea looks like a cone
Keratoconus usually appears before in the late teens or twenties. The first sign of keratoconus is an astigmatism that increases or changes frequently and which doesn’t have the regular bow tie shape when looking with corneal topography.
Corneal topography in keratoconus does not show the normal bowtie astigmatism
In the early stages glasses can be used to correct the vision. Eventually contact lenses are needed to give good vision, initially soft lenses can be used e.g. Kerasofts , however it is usual to progress to Rigid Gas Permeable lenses such as Quasar K lenses. The Synergeyes lens and the So2Clear lens are new more comfortable lenses that have designs for keratoconus.
As the disease progresses sometimes the cornea loses its ability to keep water out and what is called hydrops occurs. The scarring from hydrops can lead to loss of vision, however sometimes it improves vision as it can reduce the size of the cone. If severe a corneal graft may be required.
There are surgical treatments for keratoconus that may be able to stabilise the degeneration (contact lenses will still be needed) such as cross linking and INTACS. INTACS are plastic semi-circular segments that are inserted into the cornea in an attempt to flatten it, reducing the astigmatism and improving contact lens comfort.
INTACS are plastic semi-circular segments inserted into the cornea to flatten it
Cross linking is a relatively new treatment for keratoconus, riboflavin (vitamin B2) and ultraviolet light are used to link together the collagen fibres of the cornea leading to increased strength.
In crosslinking Riboflavin and Ultraviolet light are used to crosslink the collagen fibres and strengthen the cornea