Refractive state, intelligence, education, and Lord's paradox

•This study was conducted on a cohort of Swedish men (N = 45.906).•Myopes had higher intelligence and education than emmetropes and hypermetropes.•Emmetropes had higher intelligence and education than hypermetropes.•This last difference in education reversed when controlling for intelligence.

In a cohort of Swedish men (N = 45.906), we found that men with myopia had higher levels of intelligence and education than men with emmetropia and both these groups had higher levels than men with hyperopia. The educational advantage of myopia was reduced by 47-66 percent when adjusting for intelligence but still remained significant. When adjusting for intelligence hyperopes had a higher level of education than emmetropes. Hyperopes also had the highest level of education compared to their level of intelligence. The reversal in the difference between hyperopes and emmetropes when adjusting for intelligence could be seen as an example of Lord's paradox, possibly due to hyperopes having a higher level of intelligence than emmetropes with the same intelligence test score.