The rate of blinking varies, but on average the eye blinks once every five seconds (12 blinks per minute). Assuming the average person sleeps eight hours a day and is awake for 16 hours, he or she would blink 11,520 times a day, or 4,204,800 times a year. The average blink of the human eye lasts about 0.05 seconds.
The shape of the eye and the lens determines how light focuses on the retina. (From Willis, M.C. Medical Terminology: A Programmed Learning Approach to the Language of Health Care. Baltimore: Lippincott, Williams & Wilkins, 2002.)