Degree of myopia in relation to intelligence and educational level.

Intelligence test scores and educational levels were compared for 5943 myopic and 9891 non-myopic 18-year-old men being drafted for military service in Denmark. The former were grouped by degree of myopia, in the range -0.25 diopters (D) to -7.75 D, according to the power of correcting lenses required. Myopes of all degrees had significantly higher test scores and educational levels than non-myopes. However, the relation of these two variables to degree of myopia was not linear; for both variables there were no significant differences among myopia groups in the range -2.0 to -7.75 D. Whereas factors associated with intelligence and education seem to be important in triggering the onset of myopia, they seem to be much less important in determining the degree to which myopia progresses.