The first suggestion that the two optic nerves partially crossed in the chiasm was made by Isaac Newton in a 1682 private letter to William Briggs, a physician who had helped him dissect eyes at Cambridge. Newton later published the idea as a codicil to his Opticks of 1704. He made a drawing of the idea without publishing it, although it was discovered after his death in 1727, and later published by David Brewster in 1855.

The first actual publication of a diagram of semi-decussation was made by the famous quack John Taylor in 1738, no doubt plagiarizing Newton and ironically being closer to the truth than Newton was: congruent fibers from the two eyes run in parallel with each other after the chiasm, instead of joining there as Newton had envisioned.

No one knows how exactly Newton came to this idea. He may have experienced migrainous hemianopia. Actual clinical hemianopia was not described until Vater and Heineke’s thesis in 1723, being ignored or misinterpreted throughout the ages, just as patients often do today.

Submitted by Ron Fishman from the Cogan Ophthalmic History Society.