Oct. 14, 2023
A scientific textbook by Michael C. Brodsky, M.D., emeritus ophthalmologist at Mayo Clinic in Rochester, Minnesota, provides a comprehensive neurologic explanation for the unique eye movement disorders that afflict children with infantile strabismus and nystagmus. "The Evolutionary Basis of Strabismus and Nystagmus in Children," published by Springer, contains a collection of 20 essays that explain these disorders and consolidate the interrelationships between them.
Dr. Brodsky is a professor of ophthalmology and a professor of neurology at Mayo Clinic College of Medicine and Science and the Knights Templar Eye Foundation Research Professor of Ophthalmology at Mayo Clinic. For the past 25 years, he has been studying the enigmatic conditions that fill our pediatric ophthalmology clinics. His findings have given rise to a groundbreaking and unifying theory: These interrelated ocular motor aberrations arise from the evolutionary expression of ancestral visual reflexes.
Topics in this textbook include dissociated vertical divergence, primary oblique muscle overaction, latent nystagmus, dissociated horizontal deviation and congenital nystagmus. Each of these visuo-vestibular aberrations corresponds to one or more primitive visual reflexes in lateral-eyed animals that function to maintain vertical orientation and balance during body and environmental movement.
Dr. Stephen C. Pollock, a retired neuro-ophthalmologist at Duke University, has described Dr. Brodsky's perspective as a tectonic shift in thinking. "The impact of Dr. Brodsky's analyses and conclusions cannot be overstated. His book of essays not only provides cogent explanation for the origin of many pediatric ocular motility disorders but also demonstrates how these conditions are interrelated. His work has forever altered the field of pediatric ophthalmology."
According to Dr. Brodsky: "Infantile strabismus and nystagmus arise from primitive visual reflexes that originally served a critical function for postural orientation and balance in lateral-eyed animals. These reflexes were modulated by crossed retinal input to subcortical motion pathways, such as the accessory optic system and the nucleus of the optic tract. With the development of cortical binocular vision in higher animals, these primitive visual pathways have been superseded by binocular cortical visual pathways."
Dr. Brodsky continues: But in the setting of infantile strabismus or nystagmus, they become manifest, producing clinical disorders such as latent nystagmus and dissociated vertical divergence. Similarly, infantile nystagmus represents an optokinetic tug-of-war between the newer cortical foveal pursuit pathways and the older subcortical full-field optokinetic system." This evolutionary mechanism also explains how sensorimotor disturbances can affect the visual system in the absence of structural neurologic disease.
Dr. Brodsky's analysis and its conclusions challenge the antiquated notion that infantile strabismus necessarily represents a primary problem within the visual cortex. He presents compelling arguments that these eye movements arise instead from subcortical visuo-vestibular pathways that are normally turned off after early infancy. When these atavistic visual reflexes persist, the visual motion pathways within the developing cortex become reprogrammed or reconfigured to match the preexisting subcortical template. This cortical remodeling explains how ontogeny recapitulates phylogeny in the development of the human visual motion system. "Although this analysis is confined to the subspecialty of pediatric ophthalmology, my hope is that this compilation of essays will inspire a rethinking of pathogenesis in other fields of medicine," Dr. Brodsky says.
For more information
Brodsky MC. The Evolutionary Basis of Strabismus and Nystagmus in Children. Springer; 2021.
Refer a patient to Mayo Clinic.