Importance Esotropia greater at distance than at near can be related to abducens palsy or to divergence insufficiency. Mild abduction weakness can be difficult to detect, blurring the distinction between these 2 conditions.
Objectives To examine the clinical and eye movement findings that distinguish abducens palsy from divergence insufficiency and to account for these findings based on current knowledge of vergence neurophysiology and saccadic adaptation.
Design Retrospective medical record review.
Setting A pediatric referral center.
Participants The medical records of 32 patients with esotropia greater at distance seen during a 17-year period from August 1989 to July 2006 were reviewed.
Main Outcome Measures Details regarding age, medical history, oculomotor and neurological examinations, and result of any neuroimaging studies were recorded. Eye movements were recorded in 2 subjects using binocular video-oculography.
Results Fifteen children and 17 adults were identified; 93.3% of the children had an underlying central nervous system disorder that coincided with the onset of their esodeviation, and 23.5% of the adult patients had an underlying central nervous system disorder. Eye movement recordings in 2 pediatric patients revealed lateral incomitance suggestive of abducens palsy not detected by clinical examination.
Conclusions and Relevance The acute onset of an esodeviation greater at distance in a child is frequently associated with an underlying central nervous system disorder. Several features suggest that the children, unlike the adults, likely had a subtle abducens paresis rather than divergence insufficiency. This was confirmed by formal eye movement studies in 2 children in whom lateral incomitance was not detected clinically. The same pattern of strabismus in an otherwise healthy adult is more likely due to age-related reduction in accommodation, increased ratio of accommodative vergence to accommodation, and relative divergence insufficiency.