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The Marcus Gunn pupil is a relative afferent pupillary defect indicating a decreased pupillary response to light in the affected eye. [3] In the swinging flashlight test, a light is alternately shone into the left and right eyes. A normal response would be equal constriction of both pupils, regardless of which eye the light is directed at.
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]
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.
Ischemic optic neuropathy (ION) is the loss of structure and function of a portion of the optic nerve due to obstruction of blood flow to the nerve (i.e. ischemia).Ischemic forms of optic neuropathy are typically classified as either anterior ischemic optic neuropathy or posterior ischemic optic neuropathy according to the part of the optic nerve that is affected.
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]
Relative afferent pupillary defect OD Right eye (oculus dexter) Ret. Retinoscopy RHyperT Right hypertropia RHypoT or RHT Right hypotropia RNFL Retinal nerve fibre layer RPE Retinal pigment epithelium RSOT Right esotropia Rx Prescription SE Spherical Equivalent: SLE Slit lamp examination SLM Slit lamp microscope EP Esophoria: ET Esotropia: Supp.
Visual acuity often remains stable and poor (around or below 20/200) with a residual central visual field defect. Patients with the 14484/ND6 mutation are most likely to have visual recovery. [8] Dominant optic atrophy is an autosomal dominant disease caused by a defect in the nuclear gene OPA1. A slowly progressive optic neuropathy, dominant ...
The pupillary light reflex neural pathway on each side has an afferent limb and two efferent limbs. The afferent limb has nerve fibers running within the optic nerve . Each efferent limb has parasympathetic nerve fibers traveling along the periphery of the oculomotor nerve . The afferent limb carries sensory input.