The diagnosis of ocular paralyses / by Archibald S. Percival.

  • Percival, A. S. (Archibald Stanley), 1862-
Date:
[1897]
Catalogue details

Licence: Public Domain Mark

Credit: The diagnosis of ocular paralyses / by Archibald S. Percival. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    on covering the right eye, and directing the patient to fix an object 10 degrees to his left with his left eye, an innervation equivalent to a conjugate deviation of 30 degrees to the left will be sent out to both eyes. The left eye, therefore, turns out 10 degrees, while the right eye behind the screen will turn in 30 degrees. The secondary deviation is, therefore, much greater than the primary deviation, which is the deviation of the affected eye when the sound eye is used to tix the object. In this case, when the right eye turns inwards 10 degrees, the left eye will only turn outwards 3*3 degrees.'^ This difference between the primary and secondary deviations constitutes the essential distinction between a paralytic and a concomitant squint. Under the title of con- comitant squints are included not only the convergent strabismus of hypermetropia and the divergent strabismus so commonly seen in myopia, but paralyses of the associated movements. The dis- tinguishing feature of these squints is their concomitancy, and always implies a lesion or anomaly of action at or above the nuclear origin of the nerves. Often what is called the movement of readjustment is more readily seen and recognised than the secondary deviation, which takes place behind the screen. Suppose, as above, a secondary deviation of the right eye behind the screen of 30 degrees inwards. On removing the screen and placing it before the left eye, and on directing the patient to now fix the object with his right eye, a distinct movement outwards of readjustment of the right eye may be seen. This movement enables us to distinguish very shght paretic conditions, and a want of balance between the ocular muscles from a normal state, or one associated with apparent squint (due to an anomaly in the value of the angle a). Another common symptom in ocular paralysis is vertigo. This giddiness depends upon the diplopia, and on the false orientation ; it is often most marked on going up or down stairs. In severe cases it may even induce a tendency to vomit. This vertigo always disappears at once on closing the paralysed eye. * The measurement of the extent of the secondary deviation is the most accurate and reliable mode of estimating the progress of a case of ocular paralysis under treatment.