1. An instrument used to measure the refractive power of the eye and determine the correct lens prescription for eyeglasses or contact lenses.
Usage: Also called a refractometer in some contexts.; Used by optometrists and ophthalmologists during eye examinations.

Examples

• The optometrist used an optometer to check my vision during my annual eye exam.
• Modern optometers can automatically measure refractive errors with high precision.
• The patient sat still while the doctor looked through the optometer to find the right prescription.
• Digital optometers have largely replaced manual versions in most eye care clinics.
• The optometer helped determine that I needed glasses for reading.