IN general, people who are nearsighted do better on intelligence tests and achieve higher educational levels than those who are not, but the traditional explanation -that reading promotes nearsightedness in genetically susceptible people - may not be correct, Danish scientists say. Instead, they suggest, ''visual exploration of the near environment'' from birth may be associated with both higher intelligence and nearsightedness later in life.

In research reported in the Dec. 10 issue of The Lancet, a British medical journal, T. W. Teasdale of Copenhagen University and colleagues at the Danish Institute of Myopia Research studied the records of 18-year-old draftees in Denmark.

They were given a 78-question intelligence test and their educational achievement was coded. They were grouped according to the strength of corrective lenses they needed, if any, measured in diopters, or units of refractive power.

The researchers found that the mean intelligence test score for men who were not nearsighted was 41.41 and, on average, they had completed 10.46 years of schooling. Men who needed corrective lenses of up to 2.0 diopters had a mean test score of 45.34, with 11.06 years of schooling. Men who needed lenses of 2.25 to 4.0 diopters had a mean test score of 46.82 and had finished 11.28 years of schooling. In the most nearsighted group studied, men who needed lenses of 6.25 to 7.75 diopters, the mean test score was 47.09, the average years in school 11.43.