We blink our eyes every six seconds. Although blinking eyes ins an involuntary action, we can raise or lower the number of blinks voluntarily. Blinking our eyes automatically supplies two forms of safety to our eyes, to keep them from drying out, and to keep foreign matter from entering and irritating our eyes. The rims of our eyelids are lined with 20-30 oil-producing glands. Blinking automatically coats the eyelid and eyelashes with the lubricant it secretes, to prevent them from drying out.
When we are concentrating on a particular thing or looking continuously on a keyboard, screen, needle, etc we blink less as compare to the normal situation. This happens because our brain forgets to blink as a result our eyes feel tired. Research has shown that we blink more quickly when we are not interested in a particular task and also not taking the information inside for processing and vice versa. Some animals like the snake for example, do not have eyelids and hence cannot blink. But there is a hard film or scale over the eyes to protect them from dust and injury.