Retinoscopy is a procedure that looks in the interior of eye (retina) and measures refractive errors objectively. In order to identify whether a patient has emmetropia, myopia (nearsightedness), hyperopia (farsightedness), or astigmatism, the technique is carried out by an optometrist to assess the interior of the eye.

Retinoscopy is often done as part of a normal eye check up to asses the refractive defects in the eyes and to see if corrective lenses are required for clear vision. It is frequently used to assess vision issues in the patients who are unable to communicate properly as it is an objective process and does not call for the response from the patient. The Foucault test is the foundational concept of retinoscopy. An ideal working distance for the optometrist to examine eye is 40 cm. The retinoscopy reaction should be neutral when eye of the patient is on the target if the patient is adapting well. 

When a patient has emmetropia and can see more clearly without glasses or contact lenses, a retinoscopy may be the only test required. However, retinoscopy is typically followed by further subjective tests to identify the precise corrective lens prescription required to obtain clear vision. A device known as a retinoscope is used by optometrist to perform retinoscopy. A light source, a lens that condenses the light, and a mirror make up the retinoscope. Optometrist utilise the retinoscope during the operation to beam light through the pupil, then shift the light across each eye vertically and horizontally across each eye and observes how the light reflects off the retina. 

The way the light reflects will determine if a patient can see clearly or if they are nearsighted, farsighted or have astigmatism. In some cases the eyes may be dilated before a retinoscopy is performed. When eyes are dilated, their focusing ability is temporarily limited and the pupils are widely apart, which makes it easier for the optometrist to see how the light reflects and can lead to a more accurate diagnosis.

A retinoscope is a device used to shine a beam of light directly into the eye to assess the refractive error and determine the type of eye prescription needed. This technique is especially useful in cases where a patient cannot undergo a subjective refraction because they are unable to judge or respond.