Something that causes a response in a body part or organism. A stimulus may be internal or external. Sense organs, such as the ear, and sensory receptors, such as those in the skin, are sensitive to external stimuli such as sound and touch.
Just curious...given my insurance plan I can get a new pair of frames and lenses once every 2 years, but I realllly love glasses so I tend to purchase about 2 pair per year...Gotta have my style...oh and of course the added benefit of sight is a nice plus:)
Then starting at age 3, they should receive another eye exam. At age 6, kids should have their eyes tested every two years, and more often if their eye doctor recommends it. In general, if you wear glasses or contact lenses, the recommendation is every one to two years.