Hippus pupil in one eye8/14/2023 ![]() ![]() The light reflex pathway showing the afferent path (red) and the efferent path (blue) © John Yaw-Jong Tsai, Touro Universityġ The afferent part of the pathway (red) refers to the nerve impulse/message sent from the pupil to the brain along the optic nerve when a light is shone in that eye.Ģ The efferent part of the pathway(blue) is the impulse/message that is sent from the mid-brain back to both pupils via the ciliary ganglion and the third cranial nerve (the oculomotor nerve), causing both pupils to constrict, even though only one eye is being stimulated by the light.Ī positive RAPD means there are differences between the two eyes in the afferent pathway due to retinal or optic nerve disease. To understand how the pupils react to light, it is important to understand the light reflex pathway (Figure 1). This is called the consensual light reflex. When the light source is taken away, the pupils of both eyes enlarge equally. ![]() In other words, a bright light shone into one eye leads to an equal constriction of both pupils. The physiological basis of the RAPD test is that, in healthy eyes, the reaction of the pupils in the right and left eyes are linked. The test can be very useful for detecting unilateral or asymmetrical disease of the retina or optic nerve (but only optic nerve disease that occurs in front of the optic chiasm). The “swinging light test” is used to detect a relative afferent pupil defect (RAPD): a means of detecting differences between the two eyes in how they respond to a light shone in one eye at a time. This article explains how careful examination of the pupil light reflex can reveal valuable information about the afferent (optic nerve) and efferent (oculomotor nerve) light reflex pathway, and hence the functioning of these two cranial nerves. David C Broadway Consultant ophthalmic surgeon, Department of Ophthalmology, Norfolk & Norwich University Hospital and Honorary Reader, University of East Anglia, Norwich, UK.
0 Comments
Leave a Reply.AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |