JCAT Independent Practice Exam 2025 – The All-in-One Guide to Exam Success!

The instrument used to measure the power of spectacle lenses is known as a lensmeter. This device is essential in the optical field as it allows practitioners to determine the focal power of prescription eyewear accurately. A lensmeter typically works by shining light through the lens and using either manual or digital readings to assess how the lens refracts the light. It is particularly important in ensuring that lenses are made to the correct specifications for individual prescriptions, enabling optimal vision correction for wearers.

Other instruments mentioned serve different purposes: a distometer is primarily used for measuring distances in lens design, a tonometer measures intraocular pressure to assess eye health, and an ophthalmometer, or keratometer, measures the curvature of the cornea. Understanding the specific function of a lensmeter is crucial for anyone involved in the fitting or prescription of corrective eyewear, as it directly relates to the patient's visual needs.