Astigmatism

Astigmatism: Objects are blurred at all distances because the shape of the cornea is not uniform.
             
Contact lenses: Lenses which fit directly on the eyeball under the eyelids.
               
Cornea: The clear tissue in front of the eye resembling a crystal of a watch.
             
Refractive error: A defect in the eye that prevents light from being brought to a single focus exact on the retina.
              
Retina: Light sensitive membrane at the back of the eye. Light is focused onto this membrane and the retina then transmits this information to the brain as impulses which the brain interprets as sight.
                
Sclera: The firm white fibrous membrane that forms the white part of the eye.
             
Visual Acuity: Clarity of vision, with corrective glasses.