Progressively poor vision not easily corrected with eyeglasses. There is often a history of frequent changes in eyeglasses prescription that do not adequately correct vision. Another common progression is from soft contact lenses to toric or astigmatism correcting contact lenses, to rigid gas permeable contact lenses.

For visual improvement and astigmatism management, spectacles or soft toric contact lenses can be used in mild cases. 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, piggyback lens use ( hard lens over soft lens), scleral lenses, hybrid lenses, and PROSE (prosthetic replacement of the ocular surface ecosystem). Those patients that become contact lens intolerant or do not have an acceptable vision, typically from central scaring, can proceed to surgical alternatives.

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