High prevalence of strabismic visual field expansion in pediatric homonymous hemianopia.

If homonymous hemianopia develops in childhood it is frequently accompanied by strabismus. In some of these cases the strabismus increases the size of the binocular visual field. We determined how prevalent visual-field-expanding strabismus is in children who have homonymous hemianopia. Medical records were examined from 103 hemianopic patients with exotropia (XT) or esotropia (ET). For each participant, we determined whether their strabismus was in a direction that resulted in visual field expansion (i.e. left exotropia with left homonymous hemianopia). Ages at which hemianopia and strabismus were first noted were compared to determine which developed first. The prevalence of XT (24%) and ET (9%) with homonymous hemianopia were both much higher than in the general population (1.5% and 5%, respectively). More strabismic eyes pointed to the blind than seeing side (62 vs 41, 60% vs. 40%, p = 0.02). Exotropic eyes were five times more likely to point to the blind side than esotropic eyes (85% vs 15%). Strabismus, especially exotropia, is much more common in pediatric homonymous hemianopia than in the general population. The strabismus is significantly more often in a visual field-expanding direction. These results support an adaptive role for the strabismus. Patients with HH and exotropia or esotropia should be aware that their visual field could be reduced by strabismus surgery.
Competing Interests: The authors have read the journal’s policy and have the following conflicts: The patents (Peli E. (2008) Peripheral Field Expansion Device. US patent #7,374,284, and Peli E. (2018) Vision modification based on a multiplexing prism US Patent #10,031,346) are devices for people with visual field loss but are not related to the paper. The paper describes the naturally occurring condition, strabismic visual field expansion. Dr. Peli’s ownership of the patents does not alter our adherence to PLOS ONE policies on sharing data and materials.