Nearly half of all kids spend four hours or more a day using computers or portable electronic devices with screens, according to statistics from the nonprofit VSP Vision Care, the nation's largest eye-care benefits program. But too much screen time can lead to problems such as blurred vision and headaches. What's more, kids may be more susceptible because they may not realize—or be able to express—when they're experiencing discomfort, says New York City-based optometrist Andrea Thau, OD, a spokesperson for the American Optometric Association. To prevent problems:

• Limit screen time. Twenty to thirty minutes at a stretch is plenty for younger kids. Enforce the 20/20 rule. Have your child take a 20-second break for every 20 minutes of screen time, either by getting up and stretching or by looking out the window.
• Adjust her work-station. Ideally, the top of the computer screen should be at her eye level for the most comfortable viewing angle.
• Cut the glare. Use a desk lamp with a dimmer so there isn't a big contrast between the brightness of the room and the screen, and make sure your child can't see her own reflection on the screen.
• Get some distance. The screen should be 18 to 24 inches away from your child.
• Keep your eyes open. Your child should have regular routine eye exams, but if she rubs her eyes or complains of blurry vision after she gets off the computer, take her to the doctor for an extra check.