The pupil Flashcards
What influences the resting position of the pupil?
Sympathetic and parasympathetic innervation
What is miosis?
Constriction of the sphincter muscle in the iris by CNIII
What is mydriasis?
The iris dilator muscle dilates the pupil via sympathetic chain
What is anisocoria?
Unequal pupil size (physiologic and pathologic)
What is physiologic anisocoria? How frequent is it?
< 1mm asymmetry, both pupils equally reactive
25% of population
What is pathologic anisocoria?
> 1mm difference in asymmetry
pupils react different
pupil size difference in light vs. dark conditions
What causes mydriatic disorders? List a few
Abnormal pupil is unable to constrict causing greater asymmetry in light
CNIII palsy, acute angle closure glaucoma, Adie’s pupil , traumatic mydriasis (iris trauma or surgery), dilating/Cycloplegic drops
What causes miotic disorders? List a few
Abnormal pupil is unable to dilate, causing greater asymmetry in the dark
Horner’s, iritis, cholinergic, anticholinesterase inhibitor drugs (pilocarpine, carbachol)
What is the pathway of pupillary light reflex?
Light stimulates retina–> pretectal nucleus in the mid brain
Pretectal nucleus–> both edinger Westphal nuclei
Edinger Westphal –> ciliary Ganglion
Ciliar ganglion–> sphincter muscle in both pupils
What does RAPD indicate? ( relative afferent pupillary defect)
Damage to the afferent visual system (retina or optic nerve)
What causes RAPD? (examples)
Optic nerve disease: trauma, optic nerve glioma, glaucoma, optic neuritis
Retinal disease: retinal detachment, central retinal artery or vein occlusion
Would cataracts cause RAPD?
No
Would corneal scar cause RAPD?
No
Would refractive error cause RAPD?
No
Would vitreous hemorrhage cause RAPD?
No
