Alternating Contraction Anisocoria

Abstract

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, unrecognized pathological conditions may cause anisocoria, for example, the frequently occurring peripheral sympathetic condition.Alternating contraction anisocoria is a fleeting phenomenon, usually of small extent. It generally escapes ordinary observation and can be revealed with certainty only with the aid of pupillographic records. METHODPupillography is the recording and analysis of pupillary movements and reflexes under standard conditions. For a detailed description of the technique the reader is referred to the literature.*The clinical routine examination used in this laboratory consists of the following series of reactions, with periods of rest interposed. Series 1.-After adaptation to dark red-infrared illumination for at least six minutes, two reactions to light are elicited in which both eyes are simultaneously exposed to the stimulating light. The stimulus intensity is "standard," e. g., IS f.-c. (foot-candles) through a Wratten XI green filter, the duration being one second and the dark interval between stimuli three seconds.Series 2 and 3.-The right (Series 2) or left (Series 3) eye alone is exposed to seven con¬ secutive light stimuli, while the other eye remains in darkness. Stimulus intensity, duration, and frequency are the same as in Series 1. A psychosensory stimulus, such as sudden sound, is inter¬ posed between the fourth and fifth light stimuli of each series.1. The "first neuron," i. e., the retinal ganglion cell layer, sends its fibers through the optic nerve, optic chiasm, and optic tract to the right and left pretectal areas in the anterodorsal midbrain.2. The "second neuron" transmits the stimuli received by each pretectal area to the right and left Westphal-Edinger nuclei.3. The "third neuron" consists of the preganglionic third nerve fibers from the Westphal-Edinger nucleus to the ciliary ganglion. 4. The "fourth neuron" is composed of the postganglionic short ciliary fibers to the iris sphincter.

Inequality of the direct and consensual light reflexes in normal subjects.

“…Reflex amplitude also increased with intensity (F=348-6, P<0001) (Fig. 4b), so that contraction anisocoria, when expressed as a percentage of reflex Discussion Lowenstein (1954) described the phenomenon of the direct light reflex exceeding the consensual as 'alternating contraction anisocoria'. The term 'alternating' is, however, misleading, because there are subjects in whom the contraction anisocoria does not reverse in direction when the light is switched from one to the other eye.…”

Inequality of the direct and consensual light reflexes in normal subjects.

“…Reflex amplitude also increased with intensity (F=348-6, P<0001) (Fig. 4b), so that contraction anisocoria, when expressed as a percentage of reflex Discussion Lowenstein (1954) described the phenomenon of the direct light reflex exceeding the consensual as 'alternating contraction anisocoria'. The term 'alternating' is, however, misleading, because there are subjects in whom the contraction anisocoria does not reverse in direction when the light is switched from one to the other eye.…”

Naso-temporal asymmetry and contraction anisocoria in the pupillomotor system

“…With an asymmetric crossing in the chiasm and a predominantly contralateral midbrain projection, a larger direct than consensual pupillary reaction occurs when only one eye is illuminated. Although it was believed to be a pathologic abnormality by some investigators [28,35], this contraction anisocoria has been reported by several authors [1,35,44,55].…”

Sex-Specific Lateralization of Contraction Anisocoria in Transient Pupillary Light Reflex

“…Contraction anisocoria refers to the difference between the pupillary constrictions in the stimulated eye (direct) and the contralateral eye (consensual). It was initially considered as an abnormality in the reflex pathway, 11,12 but subsequent studies have proved that a small yet statistically significant difference in constriction amplitude between the direct and consensual eyes exists in healthy subjects. [13][14][15][16][17] The small contraction anisocoria in healthy subjects using full-field stimulation has been hypothetically attributed to the asymmetries at the two decussations, [13][14][15][16][17] as illustrated in Figure 1.…”

Inequality of the direct and consensual light reflexes in normal subjects.

“…Reflex amplitude also increased with intensity (F=348-6, P<0001) (Fig. 4b), so that contraction anisocoria, when expressed as a percentage of reflex Discussion Lowenstein (1954) described the phenomenon of the direct light reflex exceeding the consensual as 'alternating contraction anisocoria'. The term 'alternating' is, however, misleading, because there are subjects in whom the contraction anisocoria does not reverse in direction when the light is switched from one to the other eye.…”

Naso-temporal asymmetry and contraction anisocoria in the pupillomotor system

“…With an asymmetric crossing in the chiasm and a predominantly contralateral midbrain projection, a larger direct than consensual pupillary reaction occurs when only one eye is illuminated. Although it was believed to be a pathologic abnormality by some investigators [28,35], this contraction anisocoria has been reported by several authors [1,35,44,55].…”

Sex-Specific Lateralization of Contraction Anisocoria in Transient Pupillary Light Reflex

“…Contraction anisocoria refers to the difference between the pupillary constrictions in the stimulated eye (direct) and the contralateral eye (consensual). It was initially considered as an abnormality in the reflex pathway, 11,12 but subsequent studies have proved that a small yet statistically significant difference in constriction amplitude between the direct and consensual eyes exists in healthy subjects. [13][14][15][16][17] The small contraction anisocoria in healthy subjects using full-field stimulation has been hypothetically attributed to the asymmetries at the two decussations, [13][14][15][16][17] as illustrated in Figure 1.…”

Inequality of the direct and consensual light reflexes in normal subjects.

“…Reflex amplitude also increased with intensity (F=348-6, P<0001) (Fig. 4b), so that contraction anisocoria, when expressed as a percentage of reflex Discussion Lowenstein (1954) described the phenomenon of the direct light reflex exceeding the consensual as 'alternating contraction anisocoria'. The term 'alternating' is, however, misleading, because there are subjects in whom the contraction anisocoria does not reverse in direction when the light is switched from one to the other eye.…”

Naso-temporal asymmetry and contraction anisocoria in the pupillomotor system

“…With an asymmetric crossing in the chiasm and a predominantly contralateral midbrain projection, a larger direct than consensual pupillary reaction occurs when only one eye is illuminated. Although it was believed to be a pathologic abnormality by some investigators [28,35], this contraction anisocoria has been reported by several authors [1,35,44,55].…”

Sex-Specific Lateralization of Contraction Anisocoria in Transient Pupillary Light Reflex

“…Contraction anisocoria refers to the difference between the pupillary constrictions in the stimulated eye (direct) and the contralateral eye (consensual). It was initially considered as an abnormality in the reflex pathway, 11,12 but subsequent studies have proved that a small yet statistically significant difference in constriction amplitude between the direct and consensual eyes exists in healthy subjects. [13][14][15][16][17] The small contraction anisocoria in healthy subjects using full-field stimulation has been hypothetically attributed to the asymmetries at the two decussations, [13][14][15][16][17] as illustrated in Figure 1.…”