The researchers evaluated viewing distance and font size in smartphones. While wearing their usual vision correction (glasses or contact lenses), 129 smartphone users were asked to demonstrate how they would hold their device while reading a text message or a typical Internet page.
The researchers then measured the size of the text on the handheld devices. The goal was to find out whether the working distance at which users held their phones was appropriate for the font size on the devices.
The average font size was comparable to that of newspaper print for text messages, but somewhat smaller for the internet page. The average working distance for text messages was 36 centimeters (14.2 inches). This was closer than the typical near working distance of 40 centimeters (15.7 inches) when reading printed text. The average working distance when viewing a web page on a smart phone was even shorter: 32 centimeters (12.6 inches).
Holding smartphones at such close distances could place increased demands on the eye’s ability to correct for distance (accommodation) and coordination between eyes (vergence), compared to the distances typically used for reading printed text. Over time, this could lead to symptoms such as eyestrain and headaches.
“Optometrists should pay attention to the working distance at which patients hold their smart phones and perform appropriate testing at those distances,” according to the study by Mark Rosenfield and colleagues of SUNY State College of Optometry, New York.
Typically, optometrists follow a ‘1, 2, 10’ rule when prescribing vision correction—assuming a working distance of about one foot for cell phones, two feet for desktop computers, and ten feet for television viewing. The new study is one of the first to examine the working distances at which patients use smartphones or other handheld devices.
The new study suggests that patients tend to use handheld devices at closer distances compared to printed materials, which could have important implications for vision correction.
Smartphones “may present a variety of visual demands that are significantly different in terms of working distances, gaze angle, and text sizes,” Rosenfield and co-authors write.
The researchers believe that further research is needed to investigate eye’s response to prolonged smartphone use. In the meantime, the researchers believe that optometrists should ask patients in detail about how they use their handheld devices, and possibly perform further tests at those closer distances. Especially for older patients, changes in lens design may be needed to meet the visual demands of smart phones and other new technology.With mobile phones getting smarter, people are using them for a variety of purpose including sending text, reading mails, web surfing and even reading books, and in doing so they spend a lot of time watching the smartphone screen. According to a recent study, such users are putting high pressure on their eyes.
Earlier, it was assumed that only prolonged computer usage had adverse impact on our vision, sitting posture and even fingers. However, the study says smartphone is not immune to these. In-fact if recent researches are to be believed smartphones are more dangerous than the computers.
The problem is that the smartphone users reading text messages and internet pages hold their devices at a closer distance than they would for printed text. This puts a lot of strain on the eyes.
The study was published in the July issue of Optometry and Vision Science, the official journal of the American Academy of Optometry.