AMONG THE clinical cases examined in this laboratory a relatively large group showed a pupillary syndrome which I have named alternating contraction anisocoria. I have used the term contraction anisocoria in order to describe the appearance of inequality of the pupils under the influence of a pupilloconstrictor stimulus, such as light, while the term alternating is used because there is a variation as to which pupil becomes smaller. In alternating contraction anisocoria the pupil of the stimulated eye always contracts more extensively than does the consensually reacting pupil of the opposite side.
Many neurologists and ophthalmologists believe that pupillary inequality due to uneven illumination is a physiological phenomenon. Pupillographic records do not agree with this view. Apparent inequality of the pupils results from an optical illusion on the part of the observer, whereby the pupil of the dimly lighted eye seems larger than that of the brightly illuminated one. Furthermore,
LOWENSTEIN O. ALTERNATING CONTRACTION ANISOCORIA: A Pupillary Syndrome of the Anterior Midbrain. AMA Arch NeurPsych. 1954;72(6):742–757. doi:10.1001/archneurpsyc.1954.02330060078010
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