Computer video games.
Like most young people, 12-year old Princess McClure can stare at that little screen for hours.
Until a few months ago.
"Blurriness when I was playing video games on the computer and texting on my phone," Princess said. "I saw light, a lot of light; my eyes got watery."
Eye experts are seeing more younger patients with similar complaints.
It's not eye strain — it is computer vision syndrome, a condition resulting from focusing the eyes on a computer display for prolonged periods of time.
The average eye blinks about 20 times a minute. Studies show people staring at a computer screen may blink as few as six times a times a minute.
That causes the eyes to dry out.
And while it makes sense that adults working on computers all day might be at risk, experts are seeing more kids with computer-related vision problems for a somewhat different reason: The size of the screen.
"They're becoming so compact," explained Michael Burton, VSP optometrist. "So small, that the attention span is greater, they're looking at them longer, having to see smaller fonts, smaller characters, smaller images. That puts an additional stress on the eye that maybe a general computer at a desk just might not do."
In most cases, computer vision syndrome is not serious. But constantly dry eyes can cause a corneal ulcer, and that can lead to blindness.
"Reducing glare, appropriate lighting, appropriate distance, and certainly just being able to look away for a moment or two," are tips Dr. Burton offers. "I know those games can be involved, but just being able to look away for a moment or two would be good."
Experts recommend looking away from the computer screen and focusing on something in the distance about every 20 or 30 minutes.
"Always think to blink," is the advice Dr. Burton gives.
That tip alone has made a huge difference to Princess McClure, who can now text to her heart's content.
That is, when her mother lets her.