Page:Handbook of Ophthalmology (3rd edition).djvu/150

144 but the reverse obtains in the case of paralysis of the oculo-motorius on account of the number of muscles affected. The field of vision is in rapid succession falsely projected in various directions, according to the changes in the direction of vision; it is first too far on one side, then too high, then too low. The want of correspondence between the strain made upon the ocular muscles and the actual movements of the eye thereby accomplished, causes an impression upon the patient as if the surrounding objects were in motion; this gives him the sensation of dizziness, causes his gait to be very unsteady, and induces total loss of co-ordination in rapid movements.

In reference to the etiology, it should be noted that syphilis is a relatively frequent cause of paralysis of the oculo-motorius. Aside from this it may be caused, as may paralyses in general, by rheumatism, diseases of the central nervous system, changes at the base of the brain, in the orbit, etc.

The treatment is in the first place to be directed against the cause; for instance, syphilis. In other respects the treatment recommended for paralysis of the abducens is applicable.

If, after recovery from paralysis, strabismus remain, it is to be relieved by tenotomy of the rectus externus, and if there be very great loss of motion on the side of the rectus internus, it may be necessary simultaneously to bring the insertion of that muscle forward. The question of treatment is more complicated in cases where the upward and downward movements are only partially restored. Only where the vertical deviation of the eyes is very considerable do we have the indication for bringing forward the insertion of the rectus inferior or superior. Von Graefe recommended that slight defects of vertical motion be compensated for by tenotomy in the other eye of the muscle acting in the same direction, be it the rectus inferior or superior. If, for instance, the right eye squints upward and has but limited movement downward, then a tenotomy of the rectus inferior in the left eye will cause that to turn upward and limit its movement downward. If a harmonious action of the ocular muscles is thus partially, but not sufficiently established, the insertion of the rectus superior of the right eye may be set backward.