The effect of measuring corneal toroidicity with reference to the line of sight.
D001251:Astigmatism / Q000503:physiopathology; D003261:Contact Lenses; D003315:Cornea / Q000502:physiology*; D006801:Humans; D055095:Optics and Photonics; D012029:Refraction, Ocular; D014785:Vision, Ocular