6b. PUPIL REACTIONS

One of the most sensitive tests of unilateral optic nerve disease is the comparison of the pupillary reactions to light. But to pick up subtle asymmetry you need a dark room and a bright light. The light should not be "swinging" because all pupils dilate in the dark after about 300ms. Instead it should go rapidly straight across the bridge of the nose. The light should also come from perpendicular to the patient, not from below. The sensitivity of the retinal ganglion cells (and thus the optic nerve of which they comprise) reduces with increasing angle away from the perpendicular - the so-called Stiles-Crawford effect.

Remember: Dark room, bright light, perpendicular illumination, 3 seconds per pupil, and rapid passage over the nasal bridge.

[manjunathnatarajan]

Nice one, can you please make a video on triaging, emergencies & disc edema.