(Kelly of the Clue Crew shows an anatomical diagram on the monitor.)  This irregularity in the eye's surface bends the ray of light so that it can't be brought to a single focus, resulting in blurring
I will never back down [DOC] [TLE] astigmatism - Search-ID.com [PAR] ... eye comes from the Greek; (Kelly of the Clue Crew shows an anatomical 
diagram on the monitor.)