Marius Tscherning

Marius Hans Erik Tscherning (December 11, 1854 - 1939) was a Danish ophthalmologist.

He studied ophthalmology under Edmund Hansen Grut (1831-1907) in Copenhagen, later becoming an adjunct director at the ophthalmological laboratory at the Sorbonne in Paris. Tscherning spent 25 years at the Sorbonne, where he worked closely with Louis Émile Javal (1839-1907). In 1910 he returned to Denmark as a professor at the University of Copenhagen and head of the ophthalmic department at the Rigshospitalet.

Tscherning is remembered for contributions made in optical physiology. He conducted research of entoptic phenomenon, Purkinje images, the etiology of myopia, and Listing's law of ocular movement. He also designed an ophthalmophacometer, a device used to measure changes that happen in the front and back curvatures of the lens during accommodation.

He is probably best known for his theory regarding the mechanism of accommodation, of which he disagreed with the accommodation theory proposed by Hermann von Helmholtz (1821-1894). Tscherning believed that accommodation occurred through an increase of zonular pressure at the lens equator with contaction of the ciliary muscle, and therefore a bulging of the lens in accommodation was created by compression rather than by passive dilatation. Tscherning was the author of over 100 scientific articles, including a book titled Optique physiologique, published 1898 in Paris by Garré and Naud (Physiologic Optics), which was later translated into English, and "Hermann von Helmholtz et la Théorie de l´Accommodation", Paris 1909 Octave Doin, (Hermann von Helmholtz and the Theory of Accommodation) which was a critic to Helmholtz work on the same subject published in the Graefe's Archiv (volume 1, 1854).

Associated eponym

• Tscherning's ellipse: Term used in corrective lens design used to identify the combination of lens curvature and lens power which have minimal aberration.

References

• Acta Opthalmologica Scandinavica
• Accommodative Changes in Lens Diameter
• Julius Hirschberg/History of Ophthalmology, volume 11/part 1a, Wayenborgh, Bonn 1992, p.173,

 ISBN 13: 978-90-6299-441-0

• Albert, Norton & Hurtes "Source Book of Ophthalmology" Blackwell Science 1995, ISBN 0-86542-240-0