Which process is commonly used for measuring corneal astigmatism?

Keratometry is commonly used to measure corneal astigmatism because it specifically evaluates the curvature of the cornea, which is essential in determining the shape and degree of astigmatism. This instrument essentially measures the reflection of light from the corneal surface to assess its profile. With astigmatism, the cornea is not uniformly curved, leading to differences in how light is focused, which keratometry effectively captures.

Other methods, while useful in different contexts, do not focus directly on measuring astigmatism. Ultrasonography is generally used for more in-depth imaging of the eye's interior structures, tonometry assesses intraocular pressure, and pachymetry measures corneal thickness. Each of these plays a crucial role in overall eye health but does not provide the specific assessment of corneal shape necessary for identifying astigmatism.