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A relative afferent pupillary defect (RAPD), also known as a Marcus Gunn pupil (after Robert Marcus Gunn), is a medical sign observed during the swinging-flashlight test [1] whereupon the patient's pupils excessively dilate when a bright light is swung from the unaffected eye to the affected eye. The affected eye still senses the light and ...
The optic tract syndrome is characterized by a contralateral, incongruous homonymous hemianopia, contralateral relative afferent pupillary defect (RAPD), and optic atrophy due to retrograde axonal degeneration. [16] Causes of optic tract lesions are also classified into intrinsic and extrinsic forms.
When considering the possible causes for spontaneous NAION, the list includes other conditions like arteritic anterior ischemic optic neuropathy (associated with inflammation of arteries), optic neuritis (inflammation of the optic nerve), infiltrative and compressive types of optic neuropathy (where the optic nerve is invaded or pressed upon by ...
Medical examination of the optic nerve with an ophthalmoscope may reveal a swollen optic nerve, but the nerve may also appear normal. Presence of an afferent pupillary defect, decreased color vision, and visual field loss (often central) are suggestive of optic neuritis. Recovery of visual function is expected within 10 weeks.
However, if the eyes are asymmetrically affected, i.e. one eye's optic nerve is more damaged than the other, it will produce an important sign called an afferent pupillary defect. [citation needed] Defective light perception in one eye causes an asymmetrical pupillary constriction reflex called the afferent pupillary defect (APD). [citation needed]
When the optic nerve is damaged, the sensory (afferent) stimulus sent to the midbrain is reduced. The pupil, responding less vigorously, dilates from its prior constricted state when the light is moved away from the unaffected eye and towards the affected eye. This response is a relative afferent pupillary defect (or Marcus Gunn pupil). [1]
However, papillitis may be unilateral, whereas papilledema is almost always bilateral. Papillitis can be differentiated from papilledema by an afferent pupillary defect (Marcus Gunn pupil), by its greater effect in decreasing visual acuity and color vision, and by the presence of a central scotoma. Papilledema that is not yet chronic will not ...
For example, in a person with abnormal left direct reflex and abnormal right consensual reflex (with normal left consensual and normal right direct reflexes), which would produce a left Marcus Gunn pupil, or what is called left afferent pupillary defect, by physical examination. Location of the lesion can be deduced as follows: