Retinoscopy is one of the more difficult exams to master in ophthalmology. It allows us to obtain one’s refractive error objectively. This is useful in children who are too young to be tested subjectively on an eye chart, or in those who are not verbal.

The optics behind retinoscopy is elegant. In a perfectly round cornea without refractive error, light entering the eye is focused directly onto the retina. The reflection of light appears as a homogeneous red reflex to the examiner. In a hyperopic eye, the cornea is underpowered–light becomes focused behind the retina. As the examiner streaks the light through the pupils, the retinal reflex moves in the same direction as the light beam from the retinoscope–this appearance is dubbed “with motion”. With-motion is created from uncrossed light rays traversing the surface of the retina.

Conversely, myopic eyes focus light in front of the retina. Light rays on the retina are crossed, and produce a red reflex that moves in the opposite direction of the the streak (against motion).

For many people, against motion is difficult to discern, especially if there is with motion in another axis. I have probably overlooked this finding in dozens of kids with small amounts of myopic astigmatism, hopefully without dire consequences.

Last week, however, I successfully identified myopia through retinoscopy in a 5 year-old. The refraction was -1.00 + 4.50 x 085 in the right eye.

A celebration for this momentous event is in hand…

medicine ophthalmology