keratometer
Sign in to savethumb|An eye doctor examining a patient with a keratometer thumb|Typical presentations of keratoconus as detected through a keratometer thumb|Shin Nippon Nvision K-5001 Refkeratometer A keratometer, also known as an ophthalmometer, is a diagnostic instrument for measuring the curvature of the anterior surface of the cornea, particularly for assessing the extent and axis of astigmatism. It was invented by the German physiologist Hermann von Helmholtz in 1851, although an earlier model was developed in 1796 by Jesse Ramsden and Everard Home.
Article
3 sectionsContents
- Javal-Schiotz Principles
- Bausch and Lomb principles
- References
thumb|An eye doctor examining a patient with a keratometer thumb|Typical presentations of keratoconus as detected through a keratometer thumb|Shin Nippon Nvision K-5001 Refkeratometer A keratometer, also known as an ophthalmometer, is a diagnostic instrument for measuring the curvature of the anterior surface of the cornea, particularly for assessing the extent and axis of astigmatism. It was invented by the German physiologist Hermann von Helmholtz in 1851, although an earlier model was developed in 1796 by Jesse Ramsden and Everard Home.
A keratometer uses the relationship between object size (O), image size (I), the distance between the reflective surface and the object (d), and the radius of the reflective surface (R). If three of these variables are known (or fixed), the fourth can be calculated using the formula R = 2d \frac{I}{O}