keratometry

This is the technique used to measure the steepness of the cornea (the clear window that makes up the front of the eye.)  Everyone has a different corneal steepness, and this variation has a large effect on the eye’s overall focusing prescription.  Normally, the cornea is perfectly round like the surface of a basketball.  With astigmatism, however, the corneal surface is more like a football, and steeper along one axis while flatter along the other. Keratometry can measure this astigmatism.  Keratometry measurements are important when fitting for contact lenses as contacts come with different “steepnesses” and they need to fit properly. Keratometry readings are also needed before cataract surgery in order to calculate the intraocular lens implants to use.  Keratometry measurements can be performed manually or via automated machines (for example, the IOL-master machine used before cataract surgery).