4062. If, on attentively considering a neat object, it fatigues the eye, and becomes confused, or has a kind of mist before it.
4063. When small printed letters seem to run into each other, and, by looking steadfastly on them, appear double or treble.
4064. If the eyes are so fatigued by a little exercise, that we are obliged to shut them from time to time.
4065. When these circumstances occur, either separately or together, glasses should be immediately resorted to; otherwise the sight will be liable to be injured by the constant effort required.