Which process is useful for measuring corneal astigmatism?

Keratometry is the appropriate process for measuring corneal astigmatism because it specifically assesses the shape and curvature of the cornea. This technique uses a keratometer, which measures the radius of curvature of the cornea in two principal meridians. Since astigmatism is the result of an irregular curvature of the cornea, keratometry can effectively determine the presence and degree of this condition.

Other methods mentioned have different purposes. Tonometry measures intraocular pressure and is important for glaucoma diagnosis but does not provide information about corneal shape. Fluorescein staining is used primarily to detect corneal abrasions and surface damage, while pachymetry measures the thickness of the cornea, which can be relevant for certain conditions but does not address astigmatism specifically. Therefore, keratometry is the definitive tool for evaluating corneal astigmatism.