The front surface of the eye is covered with a tissue which consists of many glands. These glands secrete the tears that cover the eye surface and keep the eye moist, which is necessary for normal eye function. The tears help maintain the proper oxygen balance of the external eye structures and to keep the optical properties of the eye sharp. The normal tear layer is cleaned off and refreshed by the blinking action of the eyelids.

The blink reflex is one of the fastest reflexes in the body and is present at birth. However, our blink rate varies with different activities- faster when we are very active, slower when we are sedate or concentrating. Studies which have measured the blink rate and tearing on computer workers and noted that the blink rate dropped very significantly during work at a computer compared to before and after work. There was no significant change in tearing. The data support the fact that blink rate decreases during computer use, but also show that other tasks can decrease the blink rate.

Possible explanations for the decreased blink rate include concentration on the task or a relatively limited range of eye movements. Although both book reading and computer work result in significantly decreased blink rates, a difference between them is that computer work usually requires a higher gaze angle, resulting in an increased rate of tear evaporation. Since the main route of tear elimination is through evaporation and the amount of evaporation roughly relates to eye opening, the higher gaze angle when viewing a computer screen results in faster tear loss. It is also likely that the higher gaze angle results in a greater percentage of blinks that are incomplete. It has been suggested that incomplete blinks are not effective because the tear layer being replenished is ‘defective’ and not a full tear layer.

Office air environment is often low in humidity and can contain contaminants. This has been noted as the cause of ‘Sick Building Syndrome’. Additionally, the static electricity generated by the display screen itself attracts dust particles into the immediate area. These can also contribute to particulate matter entering the eyes, leading to dry eye symptoms.