Miosis--pupillary constriction--occurs whenever a lesion damages the parasympathetic fibers that innervate the pupillary constrictor via CN III.

Mydriasis--pupillary dilation--occurs whenever a lesion damages the sympathetic fibers that innervate the pupillary dilator through sympathetic nerves that run to the orbit (nasociliary branches to the ciliary ganglion -> short fibers)

Direct reflex -> illuminated pupil constricts (II in, III out)

consensual reflex -> non-illuminated pupil constricts since input input from one eye (II in) synapsees with both ipsilateral and contralateral CN III (via Edinger westphal nucleus)

Use the swinging flashlight test. Normally shining a light in one eye, causes the other to constrict.

Should both pupils dilate when the flashlight is moved to the other eye, then you can deduce an afferent pupillary defect (since something is causing the afferent pathway from the affected eye not to reach the the EW complex) in the eye that the flashlight is pointing to.

aka Marcus Gunn

etiology: asymmetric retinal disease or optic nerve (CN II) disease; not cataracts related

However, should the other pupil constrict when the flashlight is moved to the other eye, while the new eye dilates, then you can deduce an efferent pupillary defect

etiology: impaired parasympathetic motor innervation

accomodation - all mediated by CN III

(1) ocular convergence

(2) pupillary constriction,

(3) and thickening of the lens***

Note***: This is the one you can't see on physical exam.

upper eyelid

innervation: CN III--keeps the eye open

CN VII - shuts the eye with the orbicularis oculi muscle

sympathetic nerves innervate superior tarsal muslces (contribute to upper eyelid)

Complete ptosis: 3rd nerve palsy

Variable ptosis or diplopia:

worsens as day progresses

improves with naps or rests

etiology: ocular myastenia gravis

treatment: cholinesterase inhibitor edrophonium chloride (Tensilon)

Mild ptosis: sypathetic nerve palsy

etiology: horner's syndrome (Miosis, ptosis, anhydrosis, when andryosis is present)

Inability to close the eye: 7th nerve palsy

Loss of corneal reflex: 7th nerve palsy

Destructive visual-motor cortex lesions (infarct) - cause the eyes to look towards the side of the destructive lesion

• destructive brainstem lesion causes ipsilateral paralysis of horizontal conjugate gaze

• destructive frontal lobe lesion causes contralateral paralysis of horizonatal conjugate gaze

Irritative lesions (seizure activity) - cause the eyes to look away from the irritative lesion

Complete ptosis: 3rd nerve palsy

Variable ptosis or diplopia:

worsens as day progresses

improves with naps or rests

etiology: ocular myastenia gravis

treatment: cholinesterase inhibitor edrophonium chloride (Tensilon)

Mild ptosis: sypathetic nerve palsy

etiology: horner's syndrome (Miosis, ptosis, anhydrosis, when andryosis is present)