skio-, ski-, skia-
(Greek: shade, shadow)
An instrument for viewing the interior of the eye, particularly the retina. Light is thrown into the eye by a mirror (usually concave) and the interior is then examined with or without the aid of a lens.
A patch of light is formed on the patient's retina and by moving that patch in a given direction and observing the direction in which it appears to move after refraction by the patient's eye, the retinoscopist can determine whether the patient's retina is focused in front of, at, or behind the retinoscope's sight hole.
The refractive errors of light in the eyes refer to the ability of the eyes to change the direction of light in order to focus it on the retinas of the eyes.
Other related "dark; shadow, shade; black" units: lygo-; melan-; nigri-; nocti-; nycti-; scoto-; umbra-.