One in 16 preschoolers has visual impairment in at least one eye, suggests a new study of Australian kids.
The majority of those children 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, the authors write in the journal Ophthalmology.
"Especially if there is a significant amount of visual impairment, they will get worse," said Dr. Rohit Varma, one of the study's authors from the University of Southern California.
When kids are young, minor vision problems are "a pretty easy fix," with eye glasses, he said. However, "many of them if it's not corrected, it may not be correctable later on," Varma told Reuters Health.
Researchers from the University of Sydney led the study, giving 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 percent of those kids had visual impairment in at least one eye, and almost 3 percent 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 -- discerned from government health records -- had an increased risk of vision problems, compared to those born at a normal weight.
The overall rate of vision problems seen in this study is similar to what has been shown in studies of young kids in the U.S., the authors note.
Varma, who led one of those U.S. studies, said that together such results show that 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 at Johns Hopkins.
"There is at least some suggestion that there are environmental influences, both in terms of diet and other exposures," Repka, who was not involved in the current study, told Reuters Health.
He added that the only way to detect eye problems in many kids is to screen for them.
The United States Preventive Services Task force, a federally supported expert panel, recommends screening kids for vision problems, specifically lazy eye, at least once between age three and five.
However, at least in the U.S., "there aren't very many good methods of screening and identifying kids early," Varma said.