Patients with Keratoconus or other corneal diseases can often just not get spectacles or contact lenses that they can see clearly with.
Higher-order aberrations (HOAs), which cannot be corrected by spectacles, are more subtle and complex refractive errors than near-sightedness, farsightedness and astigmatism. These optical and anatomical irregularities can cause difficulty seeing at night, glare, halos, blurring, starburst patterns, distorted images or double vision.
Speciality contact lenses like scleral lenses can effectively neutralize many of these induced aberrations by masking the irregularities on the front part of the cornea. There is an impressive body of evidence proving the success of scleral contact lenses for visual rehabilitation of eyes with corneal and external ocular disease.