Disorders of Pupillary Reactivity: Light–Near Dissociation
Light–near dissociation occurs when a near response exceeds the greatest pupillary constriction that bright light can produce. The physiologic basis for light–near dissociation is because the near reflex bypasses the pretectal nuclei in the dorsal midbrain and descends from higher cortical centers directly to the Edinger-Westphal nuclei. Light–near dissociation may arise from a variety of causes (Table 10-3).
Afferent Visual Pathway
Optic neuropathy is the most common cause of light–near dissociation (unilateral or bilateral). It is the result of damage to only the afferent limb of the pupillary light reflex (optic nerve); the central near impulses remain unaffected.
Excerpted from BCSC 2020-2021 series: Section 5 - Neuro-Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.