The action of the external muscles of the eye and the diagnosis of ocular paralysis : Professor, Elschnig's diagram / by Duncan Matheson Mackay, M.D.Edin., clinical assistant, Royal London Ophthalmic Hospital; refraction assistant, Royal Eye Hospital, Southwark; late house surgeon, Liverpool Eye and Ear Infirmary.

  • Mackay, Duncan Matheson
Date:
[1905?]
Catalogue details

Licence: In copyright

Credit: The action of the external muscles of the eye and the diagnosis of ocular paralysis : Professor, Elschnig's diagram / by Duncan Matheson Mackay, M.D.Edin., clinical assistant, Royal London Ophthalmic Hospital; refraction assistant, Royal Eye Hospital, Southwark; late house surgeon, Liverpool Eye and Ear Infirmary. Source: Wellcome Collection.

    4/8 (page 4)
    4 the vertical meridian of the cornea, by the same contraction. . For example, isolated contraction of the right superior rectus would : (a) move the summit of the cornea upwards and inwards, and (b) incline the vertical meridian of the cornea to the left (that is, “wheel-motion” to the left). ( “ In speaking of the inclination of the vertical meridian of the cornea it is the upper extremity of this meridian which is meant.”—Swanzy.) Similarly, isolated contraction of the right inferior rectus would: (a) move the summit of the cornea downwards and inwards, and (J) incline the vertical meridian of the cornea to the right. The arrows on the horizontal line indicate the direction in which the summit of the cornea moves with isolated contraction of the external or internal rectus. Further, the starting-point of each inclined arrow on this horizontal line indicates the position in which the cornea must be in order that isolated contraction of an elevator or depressor may have the greatest elevating or depressing effect. That is to say, the rectus superior and the rectus inferior (for example) exert the greatest effect as to eleva¬ tion and depression of the cornea when the eye is in the abducted position; and the obliquus inferior and the obliquus superior exert their greatest effect as to elevation and depression when the eye is in the adducted position. Also, since the “ wheel-motion ” action of the elevators and depressors in each case is in the inverse ratio to the elevating or depressing action—the greater the elevating or depressing action the slighter the “ wheel-motion ” action and vice versa —there is evident from the diagram the position of the eye in which each elevator and depressor is able to exert the greatest “ wheel-motion” action ; that is, the rectus superior and rectus inferior exert the greatest “ wheel-motion ” action when the eye is in the adducted position and the obliquus superior and obliquus inferior exert their greatest “wheel- motion ” action when the eye is in the abducted position. The opposite of these two statements is true also—namely, that when the eye is adducted the elevating and depressing action of the elevators and depressors is least and when the eye is abducted the 1 ‘ wheel-motion ” action of these muscles is least. As a matter of fact, however, no regard needs to be paid to the “wheel-motion” in the diagnosis, by means of the diplopia, of paralysis, except in the case of the examination of the obliquus superior, the action of which muscle is best tested when the eye is adducted.