Iris (Definition) The iris is a structure within the eye that helps reduce the amount of light that reaches the retina. The iris is known as the colored part of the eye, and can be blue, brown, or any color or combination of colors in between. The iris is the portion of the eye that responds to light stimulation. ...Read more.
Scientists also speculate that caffeine may provide a mood-boosting effect that helps ease pain. Regardless of the mechanism by which it works, the data does indicate that caffeine does indeed make pain medications more effective and help ease pain.
Can caffeine cause heart problems? About three weeks ago I chugged one of those energy drinks and almost immediately after my left shoulder started hurting and i was having chest pains. A few hours later my heart started beating irregularly. I kind of pushed this aside. Then for about 2 weeks my left arm, jaw, neck, chest and back all hurt.