The benefits of blinking
Modern technology habits are fueling an increased interest in the way "screen time" affects our eyes.
According to the AOA's 2014 American Eye-Q® survey, 71% of adults spend up to seven hours per day using a computer or handheld device. And 66% of consumers use a smartphone, computer or other handheld device for reading rather than a printed equivalent.
"Many ODs are hearing complaints about eye strain, eye fatigue and dry eye," says Joan K. Portello, O.D., associate professor at the State University of New York (SUNY) College of Optometry. "The need for research is geared toward modern technology."
Dr. Portello and colleagues have undertaken such research. Most recently, they published "Blink Patterns: Reading from a Computer Screen versus Hard Copy" in Optometry and Vision Science, the Journal of the American Academy of Optometry.
Blink patterns are an important focus because they may change when people work on a computer. "Some patients have a full blink in a normal situation, but when at a computer, they have more incomplete blinks," Dr. Portello says. "The edge of the upper eyelid does not contact the lower lid. That means that a new film of tears is not spread over the entire cornea.
For the most recent study, Dr. Portello, along with fellow researchers Christina A. Chu, O.D, M.S., and Mark Rosenfield, Ph.D., wanted to compare how blink patterns change when people read from digital screens rather than from hard copy. They had subjects perform a reading task for 20 minutes on both a computer screen and hard copy.
To control conditions, the researchers used the same text for each test, kept the viewing distance and angle consistent, and made sure the lighting conditions were similar. "We also had them read aloud to ensure a valid comparison," Dr. Portello notes.
The results were somewhat surprising, she says. The mean blink rate for both computer use (14.9 blinks per minute) and hard copy (13.6 blinks per minute) were similar. So dry eye or eye strain cannot be explained simply on the basis of reduced blinking during computer use.
However, another factor may offer a clue. "Patients had more incomplete blinks when reading from the computer," Dr. Portello explains. In fact, the numbers were significantly higher: 7.02% of blinks were incomplete when subjects were reading from a computer, while only 4.33% were incomplete when they read from hard copy. This difference could help explain increased symptoms such as fatigue.
Some practical tips for ODs and their patients emerge from this research. First, the 20-20-20 rule still holds true. That means that every 20 minutes, computer or device users should look up for 20 seconds and focus on an object at least 20 feet away. In addition, she notes that patients may reduce symptoms by making a conscious effort to blink completely.
"Every once in a while, just fully open and close your eyes," Dr. Portello says. "That could really make a difference."
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