Keratoconus is a cone-shaped, non-inflammatory distortion of the central area of the cornea. It is a disease of unknown cause, although there is evidence for a genetic predisposition. It usually occurs during adolescence and slowly progresses until the age of 25 years. The disease affects both eyes, but the development time may be different for each.
The diagnosis is made clinically and confirmed by imaging methods such as corneal topography.
Keratoconus advances at varying rates and differently in each eye. Progression is generally more rapid, the earlier the age of onset. Keratoconus causes increasing blurriness and shortsightedness in vision, light sensitivity and halos and ghosting around light sources.
Progression usually occurs to an age of around 40-45 years and then tends to stabilize. On average, the most significant progression occurs in the first 15-20 years after the time of onset.
Stages of Keratoconus
Early keratoconus (Forme Fruste) has only very slight corneal distortion; it has little or no effect on the quality of vision and exhibits minimal or no progression. Spectacles are usually successful in correcting the myopia and astigmatism and give adequate vision. Soft contact lenses, spherical or with a toric correction, can be a good option for general use or just for sporting activities.
Corneal distortion increases and corneal changes typical of keratoconus can be observed. As the vision quality with spectacles decreases, rigid gas permeable contact lenses become the option for better quality vision.
The rigid gas permeable contact lens covers the corneal irregularity with a regular hard surface and neutralises 90% of the corneal distortion resulting in much clearer vision.
Substantial corneal distortion, difficulty in Contact lens fitting and tolerance. Scleral rigid gas permeable contact lenses may be useful to maintain an appropriate fitting and improve stability and comfort
Dramatic corneal distortion, substantial corneal scarring and thinning. Often there is poor vision with rigid gas permeable contact lenses, substantially reduced contact lens tolerance and usually very difficult to fit an acceptable rigid gas permeable contact lens.
Corneal transplant surgery, while still the most successful of all transplant surgeries, remains an invasive surgical procedure that has a long healing process and presents many postoperative challenges. It is also associated with a number of potential complications, including the possibility of graft failure. Younger patients with progressive keratoconus are more likely to reach a stage requiring a corneal transplant, typically in a more rapid fashion.
Corneal collagen crosslinking ( CXL), a procedure designed to harden the cornea and halt progression, is widely offered to patients today to prevent progression to the advanced and severe stages of keratoconus. It is hoped that in the future, crosslinking will significantly reduce rates of corneal transplantation and the difficulty of fitting contact lenses to keratoconus patients.
Corneal collagen cross-linking should be a first-line treatment for young patients with progressive keratoconus with the goal of reducing preventable vision loss and the need for corneal transplants.
It is important to understand that CXL alone does not correct the patient’s vision. Although the procedure is commonly associated with some flattening of the corneal curvature as well as post-crosslinking changes in refraction, patients will generally still need contact lenses to correct their vision.