What is the role of a retinoscope in optometry?

A retinoscope is primarily used to measure the eye's refractive power, which helps in determining an individual's prescription for corrective lenses. The device works by projecting a beam of light into the eye and observing the reflection (or "reflex") off the retina. As the light moves, the examiner looks for variations in the reflex to ascertain the level of nearsightedness (myopia), farsightedness (hyperopia), and astigmatism present. By doing so, an optometrist can estimate how much corrective power is needed in glasses or contact lenses to provide clear vision.

The other options focus on different aspects of eye care. Checking for color vision deficiencies involves testing methods that are not related to refractive measurement but rather assess the patient's ability to distinguish colors. Assessing the health of the cornea typically requires techniques such as slit lamp examinations rather than a retinoscope. Identifying cataracts is done through visual acuity tests and other specialized imaging rather than using a retinoscope, which is not designed for structural evaluations of the lens or any potential opacities.