Relative afferent pupillary defect
Note: The arrows represent the light.
Equal pupil sizes
Normal direct and consensual light reflexes.
Left relative afferent pupillary defect.
Normal direct and consensual reflexes.
This is a common case in pupillary examination. Always suspect this if there is no anisocoria.
The direct and consensual pupillary responses to light are normal. The swinging light test shows abnormal light response of the affected eye (initial dilatation followed by constriction). For example, if the left eye were abnormal, both pupils constrict when the light is shown into the right eye. When the light is swung to the left eye, both pupils dilate. When the light is swung back to the right eye both pupils again constrict. This reaction indicates a defect in the afferent pupillary fibres from the left eye. The near reflex is normal.
- tell the examiner that you would like to examine the fundus of the affected eye. The most common physical signs would be optic atrophy. Other possibilities include advanced glaucoma, retinitis pigmentosa, old central retinal artery or vein occlusion.
A patient with a left relative afferent pupillary defect.
1. What is the significance of a relative afferent pupillary defect?
Fig. 2 A patient with a right dilated and uncreactive pupil.
The swinging flash test shows abnormality of the right eye
(Note dilatation of the left eye when the light is swung to the right).