IJCAHPO Certified Ophthalmic Assistant (COA) Practice Exam 2026 - Free COA Practice Questions and Study Guide

Keratometry is the procedure specifically designed to measure the curvature of the anterior surface of the cornea, which is essential for determining its dioptric power. The amount of curvature directly correlates with how much light the cornea can bend, enabling the focus of light onto the retina. Keratometry provides crucial information for fitting contact lenses, planning refractive surgery, and understanding conditions such as astigmatism.

Refraction measures the overall optical power of the eye, including contributions from both the cornea and the lens, but it does not isolate the cornea's power specifically. Similarly, biometry involves measuring the dimensions of the eye (e.g., axial length) and is used primarily for assessing intraocular lens power calculations, rather than measuring corneal curvature directly. Optometry is a broader field covering various aspects of eye care, including vision assessment and corrective measures, but it does not refer to a specific procedure for measuring corneal power. Therefore, keratometry is the most accurate method for this purpose.