Knapp wrote valuable monographs on curvature of the cornea (above) and on intraocular tumours (see No. 5902). He became one of the leading ophthalmologists in America.

English translation, New York, 1869.

Knapp translated Koller's paper (No. 5678) into English and with the English translation published a large amount of supplementary material by American surgeons who had recently experimented with cocaine as a local anesthetic. In 1885 Knapp's paper was republished in book form as Cocaine and its use in opthalmic and general surgery...With supplementary contributions by Drs. F. H. Bosworth, R. J. Hall, E. L. Keyes, H. Knapp, and Wm. M. Polk. (New York: G. P. Putman's Sons, 1885). Digital facsimile of the book-form version from the Internet Archive at this link.