The 20 Prism Diopter Base Out Prism Test in Pseudostrabismus

摘要

The 20 Base Out Prism Test is one of the artillery of fusion tests used in vision and strabismus screening, and in daily pediatric strabismus practice. Its use has been described in textbooks as early as 1958, but the test has not yet been validated. We present a cohort of esotropic cases formerly diagnosed with pseudostrabismus who were tested with the 20BO test, and explore the possible explanations for their positive response rate of 100%.