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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.
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 ...
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]
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.
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]
On examination the pupillary responses may be sluggish to light. One would not expect to find an afferent pupillary defect because optic neuropathies are often bilateral and symmetric. [2] The optic disc may appear mildly hyperemic with small splinter hemorrhages on or around the disc, or may appear nearly normal.
With enlargement of the extraocular muscle at the orbital apex, the optic nerve is at risk of compression. The orbital fat or the stretching of the nerve due to increased orbital volume may also lead to optic nerve damage. The patient experiences a loss of visual acuity, visual field defect, afferent pupillary defect, and loss of color vision ...