accommodation the focus can be thrown forward, most persons with short eyeballs can see distant objects clearly by accommodating for them, and near objects that are not too near by extreme accommodation. For this reason _hyperopia_, as this condition is called, is usually not discovered until the person begins to feel the strain of the constant accommodation that is necessary whenever the eyes are open. Eyestrain usually shows itself in headaches; in fact, so large a proportion of headaches come from this cause that anyone who suffers from them at all frequently should have his eyes examined by a competent oculist. Relief for hyperopia is by means of glasses that shorten the focus and thus bring the image of distant objects forward to where the retina is in the short eyeball. [Illustration: EYE LENS--NORMAL AND DEFECTIVE _A_, normal eye; _B_, myopic eye; _C_, hyperopic eye (From Martin’s “Human Body”)] There is one other defect of vision that is so common as to call for a word; this is _astigmatism_. It is the condition in which the cornea is not curved equally in all directions; the vertical curvature may be greater or less than the horizontal. The effect is that points on objects do not focus sharply as points in the image, but as little elliptical spots. If one adjusts the accommodation so that the top and bottom edges of objects are sharp the sides will be blurred and vice versa. Usually the blurring is not great enough to be noticeable, but only enough to make the person unconsciously dissatisfied with the accommodation. He, therefore, constantly tries to improve it by changing the tension of his ciliary muscles, and so brings on eyestrain. The correction for this condition is glasses that are not equally curved in all directions, but so selected that their less curvatures shall fit in with the greater curvatures of the cornea. In fact, glasses that are curved only in one direction are usually used, this curvature being just enough to bring up the total curvature in that direction to equal the other curvatures of the cornea. It ought not be necessary to give warning that only competent persons should be allowed to examine and prescribe for the eyes. Great skill is needed to determine accurately just how far from correct the eyeball is, and unless this is known there is no means except guesswork by which to decide on a prescription.