ICM 8 a - Angelfire



ICM 8 a.m. Kang/Chu

Friday 4/6/01 Dr. Freedman

Pupils, Motility, and Visual Fields

I. Additional knowledge (Sort of clinical vignette-ish)

A. Picture of optic nerve swelling: Papilledema due to increased intra-ocular pressure (IOP) caused by malignant hypertension (HTN). Main point – Check blood pressure before ordering a MRI.

B. Picture of subconjunctival hemorrhage [total redness of a part of the sclera (white part of the

eye)]: Patient (pt) wakes up with red eye, usually spontaneous & segmental, seen in uncontrolled HTN, benign.

Vs. Conjunctivitis: It usually involves the entire sclera – not segmental.

Vs. Hyphema: Blood in the anterior chamber behind the cornea – not the sclera.

C. Picture of white hazy cornea: Refer to an ophthalmologist - bad sign

i. Causes

1. Corneal ulcer caused by amoeba, fungus, bacterial, viral, etc. When there is an infectious process of the cornea, the cornea turns white or hazy.

2. Secondary to acute increase in IOP: Referred to as steamier or hazy when the cornea looses its transparency due to changes in the fluid dynamics. Ex. Glaucoma

D. Migraine headaches

i. Characteristics

1. Visual aura

2. Bilateral transient visual loss for @ 20-30 min.

3. Episodic

4. Scintillating scotoma = blind spot with flickering lights (scotoma = blind spot)

E. Retinal/vitreous detachment

i. Characteristics

1. Momentary & periodic flashes

F. Transient visual loss

i. Amaurosis Fugax (serious condition)

1. Unilateral

2. Loss of vision for 5-10 min.

3. Subset of Transient Ischemic Attack (TIA) - i.e. stroke

4. Embolic phenomenon

ii. Migraine phenomenon

1. Bilateral

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Pupils, Visual Fields, & ocular motility

Pupils

I. Examination of the pupils PERRL

P Pupils: 20% of people have physiologic difference of the pupil size & is normal

E Equal: Probably pathologic if there are major differences (asymmetric)

R Round

RL Reactive to light

A. Diseases associated with unequal pupils

i. Horner’s syndrome: Lesion in the sympathetic pathways to the eye

a) Ptosis, miosis, and anhydrosis (drooping of the eyelid, small pupils, & decreased sweating)

b) Pathway (fig 7.3 in text): CNS ( Apical aspects of the lung ( Neck ( Branches to face ( Superior cervical ganglion ( Follows the carotid artery ( Follows the cranial nerves into the eye ( Innervates pupil & some muscles of the eyelid

ii. Anisocoria (unequal pupils):

a) Causes

▪ Horner’s syndrome

▪ Third Cranial Nerve (CN) pupil: Parasympathetic input – constricts the pupil

▪ Damage to the iris & pupil: Eye trauma, surgical trauma (ex. cataract surgery), etc. Ask it the pt had an eye surgery.

iii. Argyll-Robertson pupil (irregular pupil):

a) Associated with syphilis - “Great test question”

b) Small irregular pupils

c) Possible that it’s other manifestation of CNS disease, but most commonly due to intraocular congenital anomaly, inflammation (uveitis – inflammation inside the eye), trauma and surgery (ex. cataract surgery)

iv. After intraocular lense (IOL) implantation, thus, ask if the pt had an eye surgery to prevent misuse of MRI.

B. Pupillary light reflex: Output from eye ( Optic Nerve ( Crosses at the optic chiasm ( Cross at

brain. Hence, can cause consensual response because the signals are mixed.

*Note: Dr. Freedman said not to worry about structural details.

i. Consensual response: Shine light in one eye, both pupils constrict.

a) Basis for swinging flashlight test

b) When you swing the light back & forth between the eyes & then suddenly see a dilation of one pupil, it’s abnormal & is a sign of Marcus Gunn syndrome (Afferent pupillary defect). The weak or abnormal optic nerve shows the dilation.

c) Marcus Gunn (Sign of possible optic nerve disease): Ex. Optic neuritis – Multiple Sclerosis (common CNS disease in young people).

ii. Direct response: Shine light in one eye & the pupil constricts.

C. Poor pupil reaction to light

i. Diabetes: Because papillary sphincter doesn’t work well, bilateral

ii. Neurologic Disease: Optic nerve disease ex. Optic neuritis

iii. Sign of possible serious ocular problem: Acute angle closure & uveitis.

iv. Damage to pupil from surgery & trauma.

Visual Fields

I. General information & processing of image:

A. From visual field test, you can obtain information about ocular disease & CNS lesions

B. Pathway: Projection of retinal ganglion cells (send axons to optic nerve) primarily go to the visual

Cortex.

Retina ( Optic chiasm (divide 50-50 almost) ( Lateral geniculate nucleus ( 2 different segments of

the optic radiations (superior & inferior) ( Occipital cortex (CN V1)

C. Left visual field seen in the right side of the brain & vice versa.

D. Optic Chiasm: Separates the visual fields between the left & right brain. Dividing point between where the visual field defects will be unilateral vs. bilateral.

E. From the lateral geniculate nucleus there are two pathways – inferior (goes through the temporal lobe &

also called the Myer’s loop) & superior (goes through the parietal lobes). They go to the inferior & superior aspects of the occipital cortex respectively serving the inverted visual fields. In other words, the inferior cortex serves the superior aspects of the visual field & vice versa.

F. Visual fields are not perfectly round because of the nose.

G. Eye takes the image & inverts it, and that image is re-inverted by the brain. The left & right visual fields are split between the 2 sides of the brain.

H. Common misconception: Left eye goes to the right brain & the right eye goes to the left brain.

I. Right side of the visual field goes to the left and the left side of the each visual fields goes to the right. Essentially dividing the left side of the visual field & the right side of the visual field between the brain instead of dividing the eye between the brain. “Important concept & likely test material”

I. Visual field defects:

A. Retinal lesions: Macular degeneration, the part of the damaged retina corresponds to the part of the

visual field deficit.

B. Optic nerve lesions: Optic neuritis & glaucoma.

C. Lesions of optic chiasm and beyond: Tumors, strokes, trauma, etc.

D. Homonymous – Visual field defect is on the same side.

E. Lesions & location (fig 7.5 in text)

i. Anterior to chiasm: Monocular (unilateral) visual field defect. May not be total if not a complete lesion.

ii. Chiasm: Bilateral defect; Classically a bitemporal defect – tunnel vision; not homonymous (heteronymous)

Ex. pituitary tumor

iii. Optic tract (carry info from both eyes back to the brain): For example, if cut right optic tract, left visual field info going to the right side of the brain is transected and will develop left homonymous defect.

iv. Lesion through the Myer’s loop (inferior fibers) ( superior quadrants of the visual field lost.

v. Lesion through occipital lobe, left homonymous defect (if the lesion is on the right). May get sparing of the macular function.

F. Measuring visual field: Instead of measuring the entire field, focus on the central 30 degrees

G. Confrontational visual fields:

i. Steps in physical examination

a) PERRL

b) Visual field: Confrontational visual fields test: Test four quadrants with fingers while you are 2 ½-3 ft. from the pt. Pt. covers one eye at a time & fixates his/her vision on your nose. It is a screening test. Black out the quadrants of visual deficit.

c) Ocular ductions (up & down, left & down)

H. Computerized visual field testing: Automated visual field (can tell how dense they are too). There is a normal blind spot where the optic nerve comes in. The blind spot is always in the temporal aspect (because everything is inverted). *Note: Not referring to the anatomical position when looking through an ophthalmoscope (Referring to a visual field).

i.e. the blind spot is on the right for right eye.

i. Case example: If see a left homonymous hemianopsia, can be caused by right occipital infarct or right optic tract lesion (both posterior lesion in relation to the chiasm).

ii. Bitemporal hemianopsia (anopsia = large area of blindness): Maybe due to pituitary tumor or pituitary apoplexy (pituitary tumor that suddenly bleed compressing the optic chiasm)

iii. Macular sparing: Central vision intact.

iv. Case example: Unilateral visual field defect, therefore, lesion is located anterior to the chiasm. Causes: anterior ischemic neuropathy (stroke of the optic nerve), glaucoma, etc.

v. Case example: Left inferior quadranopsia – Lesion is located posterior to the chiasm because both visual fields are affected. The exact location maybe in the right parietal lobe or the superior aspect of occipital lobe on the right side.

Ocular motility

I. Extraocular muscles

A. Lateral rectus – CN 6

B. Superior oblique – CN 4

C. LR6SO4 and rest by CN 3 (medial rectus, superior rectus, inferior rectus, inferior oblique)

II. Ocular ductions (4 directions)

A. Elevation or supraduction vs. depression or infraduction

B. Abduction (away from nose) vs. adduction (towards the nose)

II. Cranial Nerve deficits

A. 6th nerve palsy – See a pt with a left eye that can’t abduct. Possible causes of poor abduction: 6th nerve palsy, Graves eye disease, Myasthenia gravis & orbital trauma.

i. 6th nerve palsy

▪ Microvascular disease (HTN, DM): Especially elderly due to microinfarct of nerve.

▪ Brain or orbital tumor

▪ High intracranial pressure

▪ Post-viral syndrome

▪ Head trauma

B. 3rd nerve palsy:

i. A pt. with ptosis. When looking left, the right eye can’t adduct. Can look without problem to the right. Can’t look up or down.

ii. 3rd nerve palsy: A pt. with eye pointing down & out. Lateral rectus works well, but the medial rectus has a problem (Difference in tone, so will be pulled by the normally functioning lateral rectus).

iii. The causes of 3rd nerve palsy

▪ Microvascular disease

▪ Brain tumor

▪ Head trauma

▪ Aneurysm (Only difference from 6th nerve palsy)

iv. A pt. with chronic left sided headache & drooping of her eyelid. Can’t move her eye up, down or toward her nose, but she could abduct. Her pupil on left was much larger than the right. If pupil is dilated far greater on one side, think aneurysm. Possible cause: Posterior Communicating Artery (PCA) aneurysm.

C. 4th nerve palsy (Not going to be tested over clinical presentation)

i. Misaligned vertically

ii. Causes (usually due to benign causes): Congenital, traumatic, microvascular, brain tumor (congenital & traumatic are most common)

D. Isolated loss of adduction:

i. Internuclear opthalmoplagia – Lesion of the Medial Longitudinal Fasciculus (MLF: Fibers carrying innervation just to the medial rectus of the 3rd nerve nucleus).

a) Two of the most common lesions of the MLF are Multiple Sclerosis (in young) & Cerebral

Vascular Accident (CVA: in old folks).

b) If you see a pt that has double vision, visual confusion, loss of balance, etc. and can’t adduct an eye, think of MS or stroke.

ii. Myastenia Gravis: Weak muscles and can’t keep eyes open, diplopia, etc. Can present with similar picture as above.

iii. Graves disease: Eyelid retraction, misalignment of eye due to constriction & fibrosis of extraocular muscles esp. of inferior & medial rectus muscles.

III. Eye movement problems

▪ CN palsy

▪ Orbital problem: Trauma, Graves disease

▪ Myastenia Gravis or other neuromuscular disorders

▪ CNS lesion

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