Marius Tscherning (1854-1939): his life and work in optical physiology

This article is based on Tscherning's papers, scientific protocols and letters and the many original instruments kept in the Medical History Museum in Copenhagen, Denmark.

In 1884, after his thesis concerning the frequency of myopia in Denmark, Tscherning became adjunct director of the ophthalmological laboratory at the Sorbonne University in Paris. He was called back to Denmark in 1910 and appointed professor of ophthalmology and head of the Eye Department, Rigshospitalet. He continued to work scientifically as emeritus from 1925.

Tscherning published about 100 scientific papers, mainly concerning optical physiology (i.e. the aetiology of myopia, entoptic phenomena, Purkinje pictures, the polygonal pattern provoked by corneal rubbing, etc.). He studied the law of Listing and projections depending on torsion of the eye and invented the ophthalmophacometer, which measures the changes that occur in the front and back curvatures of the crystalline lens during accommodation. Tscherning also studied aberration and calculated and constructed forward bulging periscopic (punctal) spectacle lenses. In addition, he studied colour sense, dark vision and adaptation.