lincoln in springfield

[RJNorton]

Eva, regarding this episode, Dr. Sotos writes (in The Physical Lincoln):

"With the eyes so markedly misaligned, each eye would generate an image significantly different from its partner's. Normally the brain fuses the eyes' different images into one, but in this case the difference was probably too great to do so. As a result Lincoln saw two images.

It is unclear why Lincoln experienced double vision on just these few occasions. His tiredness may have contributed: perhaps his brain found it too trying to fuse the different images from the eyes on that day.

In technical terms, Lincoln had an intermittent vertical hypertropia of the left eye, which is a type of strabismus. His head tilt is known as a Bielschowsky tilt."