One in 16 preschoolers has visual impairment in at least one eye, but this can be corrected.
The majority of children with visual impairment only had problems in one eye, and the most common causes were astigmatism, farsightedness and amblyopia, or "lazy eye".
Those findings highlight the importance of diagnosing and correcting vision problems in young kids so that their eyes are in good shape to start school, said Dr. Rohit Varma, one of the study's authors.
When kids are young, minor vision problems are pretty easy to fix with eye glasses.
Eye exams to more than 1,000 kids between the ages of two and a half years and six years.
In total, between 6 and 7% of those kids had visual impairment in at least one eye, and almost 3% had problems in both eyes.
Astigmatism, which causes blurred vision, was the most common eye problem, affecting half of kids with impairment. Farsightedness and lazy eye - when the eye has trouble making out details - were the next most common.
Boys and girls were equally likely to have vision problems, as were kids of different ethnicities. However, kids that were "low birthweight
" babies had an increased risk of vision problems, compared to those born at a normal weight.How can you help?
For kids with vision problems, getting eye glasses quickly is essential for the long run - as some of those problems may get much worse with time if left untreated.
Kids develop eye problems for a number of reasons, some possibly preventable and others not.
"I think that some of it is certainly hereditary or genetic," said Dr. Michael Repka, of the Wilmer Eye Institute.
"There is at least some suggestion that there are environmental influences, both in terms of diet and other exposures," said Repka, who was not involved in the current study.
He added that the only way to detect eye problems in many kids is to take them to the doctor and have them screened.Have you had your child screened for eye problems?