What is Keratometry doubling?

Keratometry works on the principle of recording the image size reflected from a known-sized object. The measurement of corneal radius is made using an optical doubling system where the observer has to align the images of the mires reflected from the cornea.

How do you calculate corneal astigmatism from K readings?

Corneal astigmatism that is calculated by the Sim-K: in this method, corneal astigmatism is calculated by the data from keratometry in 1–4 mm of the central cornea and the total astigmatism which is the difference between the steepest and the flattest meridian, measured by keratometry and in line with the steep …

What is Javal-schiotz keratometer?

The Javal-Schiotz keratometer is a two position instrument which uses a fixed image and doubling size and adjustable object size to determine the radius of curvature of the reflective surface.

What is Javal-schiotz?

The ophthalmometer is an ophthalmology device used to measure the radii of curvature and astigmatism of the cornea by projecting images of two test patterns onto it.

What is K reading?

Keratometry (K) is the measurement of the corneal curvature; corneal curvature determines the power of the cornea. The IOL Master also measures the axial length and other ocular parameters (such as anterior chamber depth and white-to-white measurements) and includes K readings.

What is a normal K reading?

Results: The average K was 43.57, with a range of 38.25 to 50. The average axial length was 24.04, with a range of 18.4 to 31.91. More than 90% of K values were between 40.5 and 46.5; and more than 90% of the axial lengths were between 22.5 and 26.5 mm.

What is keratometer and uses?

A keratometer, also known as an ophthalmometer, is a diagnostic instrument for measuring the curvature of the anterior surface of the cornea, which is used to assess the amount and axis of astigmatism.

How many types of keratometer are there?

There are two types of keratometers: single position Helmholtz keratometers, which are more common, and can adjust image size; and Javal-Schiotz keratometers, two-position machines that adjust object size.

What are normal K readings?

K readings. The normal maximum keratometry (K) reading (K max) is less than 49.00 D. The normal difference between K max and the steep simulated K (sim K) is less than 1.00 D. The K max should be used in the calculation of photorefractive treatments of hyperopia.