What device is used to manually determine refraction for vision correction?

The device that is used to manually determine refraction for vision correction is a phoropter. A phoropter is an essential instrument in optometry that allows eye care professionals to assess the refractive error of the patient's eyes. It consists of various lenses that can be switched out to measure the patient's vision at different strengths, helping to identify the appropriate prescription for glasses or contact lenses.

During a refraction test, the practitioner will have the patient look through the phoropter while changing lenses and presenting different options. The patient then indicates which lenses provide the clearest vision. This process helps the optometrist obtain precise measurements necessary for accurate vision correction.

Other devices mentioned serve different purposes: a retinoscope is mainly used to estimate the refractive error by observing the reflection of light off the retina without needing the patient to respond, making it useful for children or non-verbal patients. An ophthalmoscope is utilized for examining the interior structures of the eye, such as the retina and optic nerve, rather than diagnosing refractive issues. Tonometry is a test used to measure intraocular pressure to screen for glaucoma, not for determining vision correction prescriptions.