=Treatment of Eye-strain.=--The essential treatment of eye-strain consists in the wearing of proper glasses. It should be a rule, without any exception, to consult only a regular and competent oculist, and never an optician, for the selection of glasses. It is as egregious a piece of folly to employ an optician to choose the glasses as it would be to seek an apothecary's advice in a general illness. Considerably more damage would probably accrue from following the optician's prescription than that of the apothecary, because nature would soon offset the effects of an inappropriate drug; but the damage to the eyes from wearing improper glasses would be lasting. Properly to determine the optical error in astigmatic and farsighted eyes it is essential to place drops in the eye, which dilate the pupil and paralyze the muscles that control the convexity of the crystalline lens, and to use instruments and methods of examination, which can only be properly undertaken and interpreted by one with the general and special medical training possessed by an oculist. The statement has been emphasized that farsighted and astigmatic persons, up to the age of forty-five or fifty, can sometimes overcome the optical defects in their eyes by exercise of the ciliary muscle which alters the shape of the lens, and, therefore, it would be impossible for an examiner to discover the fault without putting drops in the eye, which temporarily paralyze the ciliary muscles for from thirty-six to forty-eight hours, but otherwise do no harm. After the age of fifty it may be unnecessary to use drops, as the muscular power to alter the convexity of the lens is greatly diminished. Opticians are incompetent to employ these drops, as they may do great damage in certain conditions of the eye which can only be detected by a medical man specially trained for such work. Opticians are thus sure to be caught on one of the horns of a dilemma; either they do not use drops to paralyze the ciliary muscle, or, if they do employ the drops, they may do irreparable damage to the eye. Any abnormality connected with the vision, especially in children, should be a warning to consult an oculist. Squint, "cross-eye" (_Strabismus_), as has been stated, may often result from near- or far-sightedness, and it may be possible in young children to cure the squint by the use of glasses or even drops in the eye, whereas in later life it may be necessary to cut some of the muscles of the eyeball to correct the condition. It is a wise rule to subject every child to an oculist's examination before entering upon school life.