The earliest symptom is subtle blurring of vision that cannot be corrected with glasses. (Vision can generally be corrected to 20/20 with rigid, gas-permeable contact lenses.)
Most people who develop keratoconus start out
Signs and tests
Keratoconus is often discovered during adolescence. It can usually be diagnosed with slit-lamp examination of the cornea. The most accurate test is called corneal topography, which creates a map of the curve of the cornea.
When keratoconus is advanced, the cornea will be thinner at the point of the cone. This can be measured with a painless test called pachymetry.