Final answer:
An autorefractor or automated refractor is an instrument used to estimate a patient's eyeglass prescription without requiring patient feedback, using light projections and sensors to measure refractive error.
Step-by-step explanation:
An instrument that can obtain an estimate of the patient's prescription without the patient's response is known as an autorefractor or automated refractor. This device is used in the field of optometry and ophthalmology to measure an individual's refractive error and determine their eyeglass prescription. It works by using a light that is projected into the eye, and sensors detect the reflections off the retina to gauge how light is focused. The measurements obtained by the autorefractor can be refined with additional testing by an optometrist or ophthalmologist to ensure the most accurate prescription.