Page:Popular Science Monthly Volume 12.djvu/92

 82 This condition is known as over-sight, technically, hypermetropia. When it exists in a degree beyond the adjustability of the lens, it may be recognized by object-tests and trial-glasses; but in less degrees it may escape detection by these means, because of the accommodating action of the lens. As in the case of near-sight, therefore, atropia must be employed for its exact observation.

Over-sight may, then, be defined as that condition of the eye in which parallel rays, passively transmitted by the lens, reach the retina before convergence, because of the shortened axis.

While the subjects of this malformation are numerous, some investigators finding them even to exceed largely those of the opposite condition, and while the eyes so malformed are usually not diseased, as in myopia, yet numerous local and general disturbances are found to exist in very many of the cases. These are the result of over-use, or straining of the muscle of accommodation. A special interest has recently been excited in reference to them by an address of Dr. George T. Stevens, of Albany, read last December before the Albany Institute, in which the relation of cause and effect is claimed to have been established by the author, between certain visual defects, particularly over-sight, and such functional nervous affections as neuralgia, the more common forms of headache, epilepsy, St. Vitus's dance, hysteria, and insanity. About six months previously he had presented this theory to the New York Academy of Medicine, but he then limited its application to St. Vitus's dance. These views were "new and unexpected to the profession," and were controverted by Dr. Charles S. Bull, of New York, in a paper read before the New York Medical Journal Association, in April last. He reports thirty-one cases of St. Vitus's dance in his own recent practice, in which special attention was given to the discovery of any such relation as Dr. Stevens affirms to exist. Fifteen of the thirty-one had correct and sixteen had defective vision (over-sight). Of the latter only five could be induced to purchase and wear the necessary correcting glasses. But in these five cases there should have been some improvement, at least, in the nervous symptoms consequent upon their wearing the glasses; this being, by the admission of Dr.