Professional workers, who spend more time in front of computers, undergo changes in their tear fluid similar to patients with dry eye disease, according to a new study by the School of Medicine at Keio University in Tokyo.

Researchers said that the protein - MUC5AC - is secreted by cells in the upper eyelid and makes up part of the mucus layer or "tear film" that keeps the eye moist. They found that participants with increased screen time had MUC5AC levels similar to those with dry eye syndrome.

"To understand patients' eye strain, which is one of major symptoms of dry eye disease, it is important that ophthalmologist pay attention to MUC5AC concentration in tears," said Dr. Yuichi Uchino, an author of the new study, Huffington Post reports. "When we stare at computers, our blinking times decreased compared to reading a book at the table," he told Reuters Health.

Researchers said that people staring at screens also tend to open their eyelids wider during other tasks. This action accompanied with irregular blinking can speed up tear evaporation and is associated with dry eye disease.

According to American Academy of Ophthalmology, an estimated 3.2 million women - aged 50 years and over - and 1.68 million men of the same age group are affected by the dry eye syndrome.

For the study, researchers recruited 96 Japanese office workers - about two-thirds of them men - to measure protein MUC5AC content in their eyes. Participants filled out a questionnaire about the nature of their work and symptoms of any eye problems.

The researchers found that 71 percent of men and 14 percent of women reported eye problems like irritation, burning or blurred vision and were associated with poor quality or quantity of tear film.

Participants, who sat in front of a computer screen for more than eight hours a day, had an average of 6.8 nanograms of MUC5AC per milligram of protein in each eye. It was 5.9 ng/mg of MUC5AC for people who worked with computer screens for more than seven hours per day. People, who spent less than five hours in front of computer or TV screens, had 9.6 ng/mg.

The finding is published in JAMA Ophthalmology.