Q31 - Pupillary Reaction (physiologic, pathologic)

Question 1

Pupillary reflex

Answer 1

1) Miosis (constriction):
- parasympathetic constriction of pupil. Occur via PNS efferent pathway. From Edinger-Westphal nucleus the parasympathetic part of oculomotor -> ciliary ganglion -> pupillary sphincter muscle.
2) Mydriasis (dilation)
- Sympathetic dilation of pupil. From hypothalamus -> C8-T2 -> superior cervical ganglion -> int carotid artery -> ophthalmic artery -> pupillary dilator muscle.

Question 2

Afferent pathway

Answer 2

Retinal receptors -> optic nerve -> optic chiasm -> pretectal nucleus -> edinger-westphal nucleus.
These bilateral connections makes sure that both pupils are of the same size (isocoria!) and that both will constrict even if only one eye is illuminated.
If the pupils are of unequal size = anisocoria

Question 3

Unilateral afferent pupillary defect

Answer 3

• retinal detachment/optic neuritis/glaucoma+atrophy/retinal vascular occlusion -> direct light reflex + indirect is decreased in affected eye, but near reflex is normal (accommodation for close objects). Otherwise there is isocoria w/ normal pupil size.

Question 4

Bilateral afferent pupillary defect

Answer 4

• Bilateral maculopathy or optic nerve atrophy -> delayed direct+indirect light reflexes, near reflex is normal. There is isocoria otherwise.

Question 5

Complete oculomotor palsy

Answer 5

• aneurysms, inflammation, or bleeding -> oculomotor palsy -> absent direct+indirect reflex+near reflex.
• there is a anisocoria w/dilated pupil and ptosis of affected eye.

Question 6

Adie’s tonic pupil

Answer 6

• Ex infection of ciliary ganglion -> damages parasympathetic (constrictor) pathway -> Direct&indirect reflex absent, near reflex is slow but present.
• There is a isocoria with dilated pupil in affected eye. Motility is not affected.

Question 7

Horner syndrome

Answer 7

• Disorders affecting the sympathetic (dilator) pathway. Either in hypothalamus (encephalitis), spinal chord (trauma) or in neural plexus along internal carotid (aneurysms, dissections).
• > miosis (constriction), ptosis and scalp anhydrosis.
• tested with cocaine eyedrop test (if horners, eye stays constricted) or paredrine test (stimulates 3rd sup cervical ganglion. If still no dilation, the problem is here or after it).