Retinoscopy(Ret) is a technique to obtain an objective measurement of therefractive errorof a patient'seyes. The examiner uses aretinoscopeto shine light into the patient's eye and observes the reflection (reflex) off the patient'sretina. While moving the streak or spot of light across the pupil the examiner observes therelative movement of the reflex then uses aphoropteror manually places lenses over the eye (using a trial frame and trial lenses) to "neutralize" the reflex.Static retinoscopy is a type of retinoscopy used in determining a patient's refractive error. It relies on Foucault's principle, which states that the examiner should simulateoptical infinityto obtain the correct refractive power. Hence, a power corresponding to the working distance is subtracted from the gross retinoscopy value to give the patient'srefractive condition, the working distance lens being one which has a focal length of the examiner's distance from the patient (e.g.+1.50dioptrelens for a 67cmworking distance).Myopesdisplay an "against" reflex, which means that the direction of movement of light observed from the retina is a different direction to that in which the light beam is swept.Hyperopes, on the other hand, display a "with" movement, which means that the directionof movement of light observed from the retina is the same as that in which the light beam is swept.Static retinoscopy is performed when the patient has relaxed accommodative status.This can be obtained by the patient viewinga distance target or by the use ofcycloplegic drugs(where, for example, a child's lack of reliable fixation of the target can lead to fluctuations inaccommodationand thus the results obtained). Dynamic retinoscopy is performed when the patienthas active accommodation from viewing a near target.Retinoscopy is particularly useful in prescribing corrective lenses for patients who are unable to undergo a subjective refraction that requires a judgement and response from the patient (such as children or those with severe intellectual disabilities or communication problems). In most tests however, it is used as a basis for further refinement by subjective refraction. It is also used to evaluateaccommodative abilityof the eye and detect latenthyperopia
