An important component of a comprehensive eye exam is uncovering binocular vision disorders. However, a comprehensive eye exam often doesn’t allow time to fully evaluate the condition or settle on a specific treatment. Most practices will refer out for or schedule the patient back for additional sensorimotor testing when a BV disorder is discovered. With this in mind, most BV disorders can be detected with the procedures typically performed during routine eye exams. Here are some things to consider.
Age
A strabismus always deserves further consideration at any age. In infants through early preschool years, strabismus is the primary concern as it can interfere with normal vision development. Esotropia is most common at this age and requires cycloplegic refractive error assessment and correction of any hyperopia.
In later preschool years through adulthood, non-strabismic binocular vision disorders, such as convergence insufficiency and convergence excess, also become concerning as these conditions can hinder development of scholastic skills, achievement, and work.
History
Any symptoms associated with reading or near work put me on alert for a lurking BV disorder. In addition to diplopia, it is important to ask about other more common symptoms of BV disorders (e.g. loss of place and/or having to reread often, blurred vision, headaches, eye strain, etc.). However, children often do not complain of symptoms due to avoiding near tasks; therefore, inquiring about school performance, whether the child enjoys or avoids reading, and their favorite versus disliked subjects in school can also give clues to possible BV disorders.
Testing
Most BV disorders can be detected with a careful cover test (especially at near) and near point of convergence (NPC) testing. Some considerations:
Cover Test: Use a good accommodative target for near with prism neutralization, adding prism until consistent reversal is observed! Near exo’s of 4-6pd or more, or eso’s of 4pd or more catch my attention as being significant.
NPC: 6cm or more can indicate a BV disorder.
Any of the following are considered deserving of further evaluation:
Note: This article focuses on BV disorders. Remember to test accommodative abilities also!