People who frequently use their smartphones for web surfing and text messaging could do their eyes a favor by increasing the text (font) size and holding their phones further from their eyes. Stereo 3D images present another kind of eye issue, according to two recent studies.
One study by researchers from the SUNY College of Optometry suggests that reading text on smartphones and other handheld devices causes more eye strain than reading the same text in a newspaper or book would. This is because people hold their phones closer to the eyes than a newspaper and also because of small-sized web text.
People should increase the font size on their handheld devices, especially for long sessions like when reading an eBook. This should cut down on eye strain.
Reading from short distances forces the eyes to work harder because the eyes must move closer together to maintain focus in both eyes. Reading smaller text also causes the eyes to work harder. And the harder the eyes work, the greater the likelihood of eye strain.
So his team set up a simple study to test how close 130 young adults were typically holding their phones and how large the text they were viewing was.
People usually hold a newspaper about 16 inches from their eyes. On average, the study volunteers held their phones an inch and a half closer (14.5 inches) to their eyes when reading a text message, with a font size about 10% larger than that of a newspaper. But when viewing a web page, the volunteers held their phones over three inches closer than typical newspaper distance (12.9 inches) and were reading text that averaged 20% smaller than typical newspaper text.
This suggests that web surfing on smartphones is particularly hard on the eyes.
Some people held their phone only seven inches away when reading text messages or web copy. And the smallest web copy was only 30% the size of newspaper print.
Scott MacRae is an eye surgeon and a professor of ophthalmology and visual science at University of Rochester Medical Center. While not associated with the study, Dr. MacRae finds a simple take home message from it: people should increase the font size on their handheld devices, especially for long sessions like when reading an eBook. This should cut down on eye strain.
For old-fashioned computer users, MacRae recommends using 12-point Verdana, a typeface specifically designed for computer screens.
An article on the study appears in the July 2011 issue of Optometry and Vision Science.
Stereo 3D images cause their own special brand of eye problems. Viewers have to focus their eyes both on a screen (the light source) and on images projected in front of the screen or behind it. This is unnatural, both to the eyes and to the brain, and can cause a host of problems including eye strain.
The researchers think their findings will be most useful to 3D content developers, allowing them to produce content that will cause less viewing discomfort.
They found that 3D viewers generally experience less discomfort the further they move from the image. Images that appeared in front of the screen caused the most discomfort at short distances and should be least comfortable when viewed on a smartphone or other handheld device. Images that appeared behind the screen were most uncomfortable at long distances, like those used when watching a movie in a theater.
The researchers think their findings will be most useful to 3D content developers, allowing them to produce content that will cause less viewing discomfort. But there's no reason dedicated 3D viewers can't test out the findings themselves and see if they make 3D viewing more comfortable.
An article on the study was published by Journal of Vision on July 21, 2011.