How to Wear Spectacles
In the proper use of Spectacles there is no circumstance of more importance than their position on the head. They should be worn so that the glasses may come as close to the eye as possible without touching the eyelashes; they must also be placed so that the glasses may be parallel to the paper when held in an easy position. To accomplish this, let the sides of the spectacles bear upon the swell of the head, about midway between the top of it and the ear; the eyes will then look directly through the glasses to the paper, and make the most advantageous use of them, instead of looking obliquely through them to the paper, as in numerous cases, where persons place the sides of their spectacles in contact with, or very near, their ears—in which position they produce a distorted image on the retina. The sides of the spectacles should also be placed at an equal height upon the head; and the hands being applied to the points of the sides, will generally direct their equal height, as well as allow of their opening to the full extent without injury.—Adams on the Human Eye.