Early stage. Very early in the disease process, the visual impairment caused by keratoconus is usually correctable with soft contact lenses or spectacles. These patients may gain the attention of the ophthalmologist if progressive myopic astigmatism develops, particularly with steeper-than-average keratometry or topography readings. As the disease progresses, it is often increasingly difficult to refract the patient to a crisp and clear visual acuity with soft contact lenses or spectacles.

Intermediate stage. As the disease progresses to an intermediate stage, patients usually experience vision loss that is no longer correctable with soft contact lenses or spectacles. Toric soft lenses often help with correcting some of the astigmatism; however, the increasing irregularity of the astigmatism may call for rigid, gas-permeable contacts in order to achieve truly crisp vision. Some patients require a piggyback configuration consisting of hard contact lenses worn over soft lenses to achieve adequate fit, comfort and vision. If a young patient develops progressive astigmatism between examinations, this should alert the ophthalmologist that further corneal imaging may be needed to evaluate the patient for worsening keratoconus.

Advanced stage. For patients who progress to the more advanced stages of disease, contact lens wear may become increasingly difficult and often uncomfortable due to the steepness of the cornea and difficulty in fitting the lenses. Contact lens intolerance is a common indication for corneal transplantation at this stage.

Keratoconus and ectatic corneal disorders. Diagnostic tools, classifications, management modalities, a new algorithm for management and clinical cases.