Difference between long-term contact-lens wearers and nonwearers in amplitude of the return-sweep velocity of eye movements during reading.

A Beckman Type RM Dynograph was used to record eye movements of 31 college students, 23 of whom had never worn contact lenses and 8 who had worn contact lenses for at least five years and 12 hours a day, while reading equivalent print at a distance of 33 cm. Analysis showed that the deviation indexes of .28 and .26 were comparable, meaning that these two groups showed similar return-sweep velocity amplitudes. A difference of 1.73 mm/.1 sec. between these two group means, 6.79 vs 5.06, respectively, was significant, implying that, while wearing contact lenses improved visual efficiency, it adversely affected reading speed. Further, other tasks involving rapid scanning such as scanning the roadway ahead while driving might similarly be affected.