[1] After returning to the United States, he settled into a private practice in New York, and became one of America's leading clinical neurologists.

Tay first described the red spot on the retina of the eye in 1881, while Sachs provided a more comprehensive description of the disease, and in 1887 noted its higher occurrence in Ashkenazi Jews from Eastern Europe.

[2][3] Sachs published several books, including Nervous and Mental Disorders from Birth through Adolescence, a reference work intended for professionals.

[1] His portrait was painted in the winter of 1914–15 by the Swiss-born American artist Adolfo Müller-Ury (1862–1947), but is presently unlocated.

Another portrait, by Marie Rosenthal-Hatschek (1871–1942), hangs in the Oskar Diethelm Library at Weill Cornell Medical College.