Marius Tscherning
Encyclopedia
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 contraction 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).
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
ophthalmologist.
He studied ophthalmology under Edmund Hansen Grut
Edmund Hansen Grut
Edmund Hansen Grut was a Danish ophthalmologist born in Copenhagen.In 1857 he earned his medical doctorate at the University of Copenhagen, and afterwards traveled to Berlin, where he studied with Albrecht von Graefe...
(1831-1907) in Copenhagen
Copenhagen
Copenhagen is the capital and largest city of Denmark, with an urban population of 1,199,224 and a metropolitan population of 1,930,260 . With the completion of the transnational Øresund Bridge in 2000, Copenhagen has become the centre of the increasingly integrating Øresund Region...
, later becoming an adjunct director at the ophthalmological laboratory at the Sorbonne
Sorbonne
The Sorbonne is an edifice of the Latin Quarter, in Paris, France, which has been the historical house of the former University of Paris...
in Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
. Tscherning spent 25 years at the Sorbonne, where he worked closely with Louis Émile Javal
Louis Émile Javal
Louis Émile Javal was a French ophthalmologist born in Paris. Originally trained as a civil engineer, he switched to the medical profession, receiving his degree from the University of Paris in 1868. Following graduation he travelled to Berlin and studied under Albrecht von Graefe...
(1839-1907). In 1910 he returned to Denmark as a professor at the University of Copenhagen
University of Copenhagen
The University of Copenhagen is the oldest and largest university and research institution in Denmark. Founded in 1479, it has more than 37,000 students, the majority of whom are female , and more than 7,000 employees. The university has several campuses located in and around Copenhagen, with the...
and head of the ophthalmic department at the Rigshospitalet
Rigshospitalet
Rigshospitalet - Copenhagen University Hospital, or simply Riget, is the national hospital of Denmark, located in the capital city of Copenhagen, between the streets of Blegdamsvej, Tagensvej and Nørre Allé...
.
Tscherning is remembered for contributions made in optical physiology
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
. He conducted research of entoptic phenomenon
Entoptic phenomenon
Entoptic phenomena are visual effects whose source is within the eye itself. In Helmholtz's words:...
, Purkinje images
Purkinje images
Purkinje images are reflections of objects from structure of the eye. They are also known as Purkinje reflexes and as Purkinje-Sanson images. There are at least four Purkinje images that are visible on looking at an eye. The first Purkinje image is the reflection from the outer surface of the cornea...
, the etiology
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
of myopia
Myopia
Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...
, 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
Lens (anatomy)
The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a...
during accommodation
Accommodation (eye)
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image on an object as its distance changes....
.
He is probably best known for his theory regarding the mechanism of accommodation
Accommodation reflex
The accommodation reflex is a reflex action of the eye, in response to focusing on a near object, then looking at distant object , comprising coordinated changes in vergence, lens shape and pupil size...
, of which he disagreed with the accommodation theory proposed by Hermann von Helmholtz
Hermann von Helmholtz
Hermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions to several widely varied areas of modern science...
(1821-1894). Tscherning believed that accommodation occurred through an increase of zonular
Zonule of Zinn
The zonule of Zinn is a ring of fibrous strands connecting the ciliary body with the crystalline lens of the eye....
pressure at the lens equator with contraction of the ciliary muscle
Ciliary muscle
The ciliary muscle is a ring of striated smooth muscle in the eye's middle layer that controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humour into Schlemm's canal. It changes the shape of the lens within the eye not the size of the pupil which is...
, 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 lensCorrective lensA corrective lens is a lens worn in front of the eye, mainly used to treat myopia, hyperopia, astigmatism, and presbyopia. Glasses or "spectacles" are worn on the face a short distance in front of the eye. Contact lenses are worn directly on the surface of the eye...
design used to identify the combination of lens curvature and lens power which have minimal aberration.