Abstract
As part of a large-scale research project investigating the relationships between vision and driving over 17.000 subjects, of both sexes and ranging in age from 16 to 9.2 were administered a distance phoria test utilizing a modified Thorington apparatus and red Maddox rod. Analysis of the resultant data reveals a slight but statistically significant trend toward exophoria with increasing age: however, this trend is not a consistent one, and is more pronounced for women than it is for men. The findings are discussed and compared with the results of previous studies.