There is a positive correlation between sexual intracourse and diminished distance vision. (We developed the term in the 1960s to refer to masturbation, which at the time remained much maligned.) In conjunction with the University of Tuscaloosa, my research assistant Groovy Jones and I worked with student body volunteers and discovered that chronic masturbators tended to be nearsighted. The cause, however, was not the act of intracourse itself, rather the tendency of the masturbator to focus his/her vision on the immediate surroundings to the exclusion of the beautiful, wide world.
To prevent nearsightedness, we propose the following behavioral changes for those who routinely engage in sexual intracourse:
1) Do it outside. It is unhealthy to be in a place where one's vision is limited by a nearby wall, ceiling, or floor.
2) During the act, take moments - preferably from ten to twenty seconds - to focus on a distant object. Allow your vision to readjust to distances. Since sex can alter time perceptions, count out loud.
3) Enjoy, enjoy, enjoy! Share your newfound freedom from nearsightedness with your friends. While we don't recommend YouTube, a well-considered blog entry or tweet may encourage others to also engage in safe sexual intracourse.