A phoria (or latent deviation) only appears when binocular viewing is broken and the two eyes are no longer looking at the same object.

On near fixation the affected individual may have only a latent deviation and be able to maintain binocularity or have an esotropia of a smaller size.

He consulted eye specialist Patrick Trevor-Roper, who diagnosed a latent squint and recommended that Chatwin take a six-month break from his work at Sotheby's.

Duane's name is associated with a few medical eponyms, including "Duane's parallax test", "Duane's retraction syndrome" and "Duane's prism test for latent squint".