Keratoconus (KCN) is a progressive bilateral corneal ectatic disorder. It manifests as characteristic cone-like steepening of the cornea associated with irregular stromal thinning, resulting in a cone-like bulge (protrusion) and significant loss of vision. The manifest clinical onset of keratoconus (KCN) may occur at puberty (late teens for male and early twenties for female population) and may progress (continuous stromal thinning and corneal steepening) until the third to fourth decade. Beyond this age, it is very rare that there is any progression.
The etiology and pathogenesis of KCN are not known. Several associations have been identified, which include rigid gas permeable (RGP) contact lens wear, chronic eye rubbing, Down syndrome, atopic disease, Leber congenital amaurosis,connective tissue disease, tapetoretinal degeneration, and inheritance.Persistent eye rubbing appears to either cause or exaggerate KCN. Persistent eye rubbing and hard contact lens wear may induce mechanical trauma that may be associated with keratoconus progression in individuals that are genetically predisposed.
Clinical findings that are associated with KCN are, by order of importance, the asymmetrical thinning of the corneal stroma and the highly irregular corneal topography, which is often (wrongly) reported as steep astigmatism. Other clinical findings that can be observed biomicroscopically include the Fleischer iron rings, Munson sign, Rizzuti sign, and/or Vogt striae.
The two most significant presentations are irregular corneal astigmatism and focal stromal thinning.The corneal thinning and the asymmetric astigmatism both occur in the area of the corneal protrusion, which is often infero-temporal. Thus topography, tomography, and pachymetry are the prime diagnostics used in the diagnosis and evaluation of KCN,in addition to biomicroscopic (slit-lamp) evaluation.
The available options for the management of KCN are highly dependent on the stage of the disease and its progression. If the disease is stabilized (no progression), the emphasis is given in correcting the vision. If the disease is progressing, the emphasis is to slow (arrest) the procession.
Since the effects of KCN in cornea shape distortion and stromal thinning are highly asymmetric, vision correction with spectacles and with spherical/toric soft contact lenses is suboptimal and only applicable to the early stages of KCN. Custom-designed soft contact lenses which incorporate aberration-controlled designs may provide some control of the primary aberrations associated with KCN such as spherical aberration such as
1. Rigid gas permeable (RGP) contact lenses.
Furthermore,
2. Corneal collagen cross-linking (CXL)is a minimally invasive outpatient procedure that has been shown to be effective in the arrest of the progression of KCN.
Keratoconus is primarily managed by eye surgeons at our R & R Eye Care Hospital. Today, several treatments are available including corneal transplant. So far no treatment is ideal and patient selection is important. In our hospital an interprofessional team is best for your followup involving both the specialists and primary care providers.
