Marius Hans Erik Tscherning (11 December 1854, in Østrup near
Odense
Odense ( , , ) is the third largest city in Denmark (after Copenhagen and Aarhus) and the largest city on the island of Funen. As of 1 January 2025, the city proper had a population of 185,480 while Odense Municipality had a population of 210, ...
– 1 September 1939) was a
Danish ophthalmologist
Ophthalmology (, ) is the branch of medicine that deals with the diagnosis, treatment, and surgery of eye diseases and disorders.
An ophthalmologist is a physician who undergoes subspecialty training in medical and surgical eye care. Following a ...
.
Tscherning first studied with
Peter Ludvig Panum
Peter Ludvig Panum (19 December 1820 – 2 May 1885) was a Danish physiologist and pathologist born on the island of Bornholm in Rønne. He founded studies in exercise physiology at the University of Copenhagen. The Panum Institute in Copenh ...
.
[O’Shea, R. P., Roeber, U., & Wade, N. J. (2017). On the discovery of monocular rivalry by Tscherning in 1898: Translation and review. i-Perception, 8(6), 1-12. https://doi.org/10.1177/2041669517743523] Then he studied ophthalmology under
Edmund Hansen Grut (1831–1907) in
Copenhagen
Copenhagen ( ) is the capital and most populous city of Denmark, with a population of 1.4 million in the Urban area of Copenhagen, urban area. The city is situated on the islands of Zealand and Amager, separated from Malmö, Sweden, by the ...
. Later Tscherning became an adjunct director at the ophthalmological laboratory at the
Sorbonne in
Paris
Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...
. 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
The University of Copenhagen (, KU) is a public university, public research university in Copenhagen, Copenhagen, Denmark. Founded in 1479, the University of Copenhagen is the second-oldest university in Scandinavia, after Uppsala University.
...
and head of the ophthalmic department at the
Rigshospitalet
Rigshospitalet (meaning ''the National'', ''State'', ''Kingdom'' or ''Hospital of the Realm'', but not usually translated) is the largest public and teaching hospital in Copenhagen and the most highly specialised hospital in Denmark. The hospital ...
.
[Salmonsens konversationsleksikon]
(biography)
Tscherning is remembered for contributions made in optical
physiology
Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...
. He conducted research of
entoptic phenomenon
Entoptic phenomena (), occasionally and incorrectly referred to as entopic phenomena, are visual effects whose source is within the human eye itself.
In Helmholtz's words: "Under suitable conditions, light falling on the eye may render visible, ...
,
Purkinje images
Purkinje images are reflections of objects from the structure of the eye. They are also known as Purkinje reflexes and as Purkinje–Sanson images. At least four Purkinje images are usually visible in the normal eye. The first Purkinje image (P ...
, the
etiology
Etiology (; alternatively spelled aetiology or ætiology) is the study of causation or origination. The word is derived from the Greek word ''()'', meaning "giving a reason for" (). More completely, etiology is the study of the causes, origins ...
of
myopia
Myopia, also known as near-sightedness and short-sightedness, is an eye condition where light from distant objects focuses in front of, instead of on, the retina. As a result, distant objects appear blurry, while close objects appear normal. ...
, and
Listing's law
Listing's law, named after German mathematician Johann Benedict Listing (1808–1882), describes the three-dimensional orientation of the eye and its axes of rotation. Listing's law has been shown to hold when the head is stationary and upright and ...
of ocular movement. He discovered the phenomenon of
monocular rivalry
Monocular rivalry is a phenomenon of human visual perception that occurs when two different images are optically superimposed. During prolonged viewing, one image becomes clearer than the other for a few moments, then the other image becomes clea ...
in which two superimposed images fluctuate in clarity or visibility.
He also designed an ophthalmophacometer, a device used to measure changes that happen in the front and back curvatures of the
lens
A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'') ...
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
Hermann Ludwig Ferdinand von Helmholtz (; ; 31 August 1821 – 8 September 1894; "von" since 1883) was a German physicist and physician who made significant contributions in several scientific fields, particularly hydrodynamic stability. The ...
(1821–1894). Tscherning believed that accommodation occurred through an increase of
zonular pressure at the lens equator with contraction of the
ciliary muscle
The ciliary muscle is an intrinsic muscle of the eye formed as a ring of smooth muscleSchachar, Ronald A. (2012). "Anatomy and Physiology." (Chapter 4) . in the eye's middle layer, the uvea ( vascular layer). It controls accommodation for vie ...
, and therefore a bulging of the lens in accommodation was created by compression rather than by passive
dilatation. Furthermore, he stated that during accommodation, while the central part of the anterior surface of the lens is bulged, the peripheral portion of the lens is flattened.
Tscherning was the author of over 100 scientific articles, including a book titled ''Optique physiologique'', published in 1898 in
Paris
Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...
by Garré and Naud, and was later translated into English
''Physiologic optics'', and ''Hermann von Helmholtz et la Théorie de l´Accommodation'', Paris 1909 Octave Doin, ("Hermann von Helmholtz and the Theory of Accommodation") which was critical to Helmholtz's work on the same subject, published in the Graefe's Archiv (volume 1, 1854). In 1894 he published ''Œvres ophthalmologiques de Thomas Young'' ("Ophthalmological oeuvres of
Thomas Young").
[
]
Associated eponym
* "Tscherning's ellipse": A term used in corrective lens
A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glasses or "spectacles" are w ...
design. A graphical representation of the front surface power as a function of total lens power in best-form lenses.Medical Dictionary
Tscherning ellipse
References
*
ttp://www.iovs.org/cgi/content/full/47/1/278 Accommodative Changes in Lens Diameter* Julius Hirschberg/History of Ophthalmology, volume 11/part 1a, Wayenborgh, Bonn 1992, p. 173,
* Albert, Norton & Hurtes "Source Book of Ophthalmology" Blackwell Science 1995,
{{DEFAULTSORT:Tscherning, Marius
Danish ophthalmologists
1854 births
1939 deaths
Academic staff of the University of Paris