Keratoconus is a corneal condition where the central or peripheral cornea becomes progressively thin and irregular shaped.
The surface of the cornea is where light begins its journey into the eye. The smoothness and shape of the cornea is vital to its function. The irregular shaped surface scatters the light entering the eye and causes distorted vision.
Although Keratoconus is variable in its progression for each individual, in some cases the dysfunction of vision can be devastating. Onset is often in early adolescence and progresses into the mid-20’s and 30’s after which it stabilises. The majority of cases of keratoconus are bilateral, and often each eye is affected differently and in some cases only one eye is affected.
There is typically a history of frequent changes in vision which are not adequately corrected with eye glasses.
Diagnosis can be made by slit-lamp examination and observation of inferior corneal protrusion. Unfortunately it is commonly misdiagnosed in mild cases. A computerised corneal topographer is useful in making an accurate diagnosis and assessment of its severity.
In a small number of severe cases, the cornea will swell and cause a sudden and significant decrease in vision which is called Hydrops. The Hydrops may last for weeks or months as the crack heals and is gradually replaced by scar tissue.
The goal of treatment is primarily to provide functional visual acuity.
1. Special designed RGP lens
Initially spectacles or soft toric contact lenses in mild cases can be used. Rigid gas permeable contact lenses are needed in the majority of cases to neutralize the irregular corneal astigmatism. The majority of patients that can wear hard or gas-permeable contact lenses have a dramatic improvement in their vision. Specialty contact lenses have been developed to better fit the irregular and steep corneas found in keratoconus; these include ( but not limited to) RoseK, custom designed contact lenses ( based on topography and/or wavefront measurements), semi-scleral contact lenses and sceral lenses.
Although there are no medicines that can prevent the disorder from progressing, a treatment called cross linking has been developed in order to harden the cornea to halt changes in the corneal shape.
2. Cross linking
A surgical procedure used in an attempt to make the cornea stronger. The procedure involves applying B2 vitamin to the eye and then using a ultra violet A light source for thirty minutes to activate chemicals that have the effect of strengthening the cornea.
In a few cases, a corneal transplant is necessary. Those patients who do not have acceptable vision, typically from central scarring, can proceed to surgical alternatives.
Recently another procedure called Intacs or kera ring implants seem to show promising outcomes. It involves implanting semi-circular rings to flatten the bulging curve of the cornea. The procedure only requires day surgery and results in improved vision in up to 90% of those patients for whom the procedure is suitable.
After a corneal transplant or Kera rings, eyeglasses or scleral lenses are often still needed to correct vision because the procedures do not always get rid of the pre-existing refractive error.