Diplopia

DIPLOPIA (from Greek diploos-double and ops-eye), double vision observed in paralysis and paresis of the eye muscles, is of great importance in determining which of the eye muscles is affected in a given case. Method of examination: a red glass is placed before one eye of the patient, while the other eye remains uncovered; at a distance of 2 meters, a burning candle is shown to the subject, moved in vertical, horizontal, and diagonal directions; on a special diagram, those directions in which double vision appears are marked (see figure). - Diagnosis is determined by two rules: first, diplopia occurs during those movements in which the affected muscle participates; second, the false image is projected in the direction in which the affected muscle should act. 1 Left eye Right eye Rectus externus Rectus internus Rectus superior Rectus inferior Obliquus superior Obliquus inferior Location of true and false images in diplopia. (From Rossolimo.) Example: double vision is observed when looking to the right; it is necessary to determine which muscle is paretic. Using the first rule, it can be said that in the given example, double vision depends either on paresis of the external rectus muscle of the right eye or on paresis of the internal rectus muscle of the left eye. The second rule allows for clarification of the diagnosis. If the image belonging to the right eye is to the right of the image belonging to the left eye (so-called homonymous diplopia), then the external rectus muscle of the right eye is affected. If the images are crossed, i.e., the image belonging to the right eye is to the left of the image belonging to the left eye (so-called crossed diplopia), then there is a lesion of the internal rectus muscle of the left eye. I. Filimonov.