Javal's rule
Javal's Rule
Javal's rule (/ʒævəl/; from the French ophthalmologist Émile Javal), also known as the rule of Scheiner or Scheiner's rule, is a principle in optometry and ophthalmology that describes the relationship between the refractive power of the cornea and the lens in the human eye.
Etymology
The rule is named after Émile Javal, a French ophthalmologist who made significant contributions to the field of ophthalmology in the late 19th century. The alternate name, Scheiner's rule, is derived from Christoph Scheiner, a German Jesuit priest, physicist, and astronomer who made significant contributions to the field of optics in the early 17th century.
Definition
According to Javal's rule, for every diopter of corneal astigmatism, there is approximately 0.5 diopters of lenticular astigmatism in the opposite direction. This rule is used to estimate the total astigmatism of the eye when only the corneal astigmatism is known.
Related Terms
- Astigmatism: A common vision condition that causes blurred vision due to the irregular shape of the cornea or the lens inside the eye.
- Diopter: The unit of measurement of the optical power of a lens or curved mirror.
- Cornea: The transparent front part of the eye that covers the iris, pupil, and anterior chamber.
- Lens: A transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina.
See Also
External links
- Medical encyclopedia article on Javal's rule
- Wikipedia's article - Javal's rule
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