Neuro-Ophthalmology

dual innervation of the Iris

1. The parasympathetic nervous system innervates the pupillary constrictor fibers via cranial nerve III. 2. The sympathetic nervous system innervates the pupillary dilator fibers via sympathetic nerves that run to the orbit.

The direct ophthalmoscope magnifies the retinal fundus by about xx times. sig?

14 As a result, the area of retina that is visible at any one time is limited (approximately 5 degree field of view).

The -- CN innervates the levator palpebrae and elevates the upper eyelid.

3

eye muscle movement & innervation

3- occulomotor 4- troclear 6- Abd

Marked persistent ptosis of the upper eyelid develops in -- cranial nerve lesions. will pupil be dialated

3rd The pupil may or may not be dilated depending on the cause and location of the 3rd nerve lesion.

3rd CN paralysis causes ? eye appear?

3rdCN palsy -> horizontal and vertical diplopia Deviates down and out during forward gaze Unable to turn eye medially Ptosis ≥3 mm Ischemia (HTN or diabetes) or nerve compression

4th CN paralysis - symptoms? due to? (2)

4thCN palsy ->vertical diplopia Upward and slightly rotated during forward gaze Upward nasal deviation when looking toward nose Head tilts away from affected eye ( objects appear tilted) Ischemia (DM or HTN), trauma, tumor Due to microthrombi in the vasa vasorum due to diabetes mellitus or hypertension

Occlusive Amblyopia

Develops because vision in one eye is occluded by cataract or retinoblastoma Causes the most severe type of amblyopia Occlusion must corrected by 1 year of age

posterior subcapsular cataract - location, which vission effected? risk factors ( 3), symp (3)

Develops in posterior cortex Decreases near vision Chronic corticosteroid use, diabetes and smoking Develops more rapidly than other cataracts Patients complain of rapidly progressive blurring halos, image distortion and glare

Do Disorders of the optic nerve or retina produce pathologic anisocoria ? and why?

Do not produce pathologic anisocoria because the signal in each of the two 3rd cranial nerves is identical since it represents the summation of light intensity from both eyes.

Strabismus - due to? normal till age? if acquired?

Eye misalignment Developmental -lazy eye due to poor muscle control Normal infants have intermittent strabismus until 4 months of age Acquired -CN lesion

Phoria

Eye misalignment only when binocular vision is interrupted by covering one eye Esophoria Exophoria Hyperphoria Hypophoria

Tropia

Eye misalignment when both eyes open Esotropia -> inward deviation of eye Exotropia -> outward deviation of eye Hypertropia -> upward deviation of eye Hypotropia ->downward deviation of eye

Nuclear Cataract - freq, location, risks factors, Symp (4)

Most common type Occurs in center of nucleus UV light and smoking Makes lens thicker and briefly improves near vision (2ndsight) Patients complain of faded blue colors, blurred vision, glare, decreased visual acuity particularly at night.

Cup to disk ratio

Normal cup to disc ratio≤0.5

The physiologic cup

is a small white depression devoid of nerve fibers in the center of the optic disc from which retinal vessels appear to emerge.

Presbyopia

is blurred near (reading) vision that occurs with aging. It is due to an inability of the lens to accommodate (thicken) for focus on near objects. Presbyopia begins in most people by age forty.

Anisocoria

is the term used to describe an inequality of the pupils with respect to size

Mobius' sign? due to?

is weakness of ocular convergence during NEAR accommodation (about 5 inches away) - develops in Graves' hyperthyroidism due to a myopathy of the medial recti.

Retinal arterioles and venules do not supply or drain the

macula

aquired color blindness due? (3)

macular disease, optic nerve inflammation or stroke of ventral occipital lobe

Sundowning

may be present normally during the first few weeks of life, and particularly in premature infants.

Sympathetic nerve palsy causes -3-- of the upper eye lid - if it is accompagned with anhidrosis - called?

mild ptosis of the upper eyelid, pupillary constriction (miosis) and normal extraocular movements. This complex of findings is termed Horner's syndrome when it is associated with anhidrosis (loss of facial sweating).

Argyll-Robertson pupils B/U/L Fail to ---- in ---- light ok with?

occur bilaterally No prob with accomodation (rapidly constrict to near vision) Fail to constrict in bright light (light-near dissociation). usually smaller than normal and also fail to dilate fully in dim light.

Binocular diplopia is caused by a disruption of

ocular alignment that is alleviated by covering either eye.

Pinhole test

only the axial rays of light pass through the central part of the cornea and lens, thereby minimizing the effects of uncorrected refractive error. The patient's vision should normalize. - will not work with catarax

Pallor is a sign of ? due to?

optic atrophy that may be due to a lesion between the retina and the lateral geniculate body.

Bilateral optic atrophy Causes of optic atrophy: (4)

optic nerve ischemia, medication toxicity, optic nerve compression radiation damage

The 7th cranial nerve innervates ----- ( eye lid muscle) A destructive lesion involving the 7th cranial nerve results in (2)

orbicularis oculi muscle that closes the upper eyelid. A destructive lesion involving the 7th cranial nerve results in the inability to close the eye and loss of the corneal reflex.

The efferent limb of the light reflex is carried in

parasympathetic fibers of the 3rd CN that terminate in the pupillary constrictor muscles of the iris.

anisocoria that increases in the bright indicates sym/parapathetic denervation of the dilator muscles.

parathymp

size of pupils and age

pupil decreases with aging (averaging 7 mm at 10 years; 6 mm at 30 years; and 4 mm at 80 years).

The retinal nerves are nourished by

retinal branches of the central retinal artery

simple anisocoria - when you will have to worry?

slight variation in size up to 1 mm (simple anisocoria) is considered normal in dim light. When abnormal anisocoria is present, the difference in size between the pupils exceeds 1 mm in dim light.

Pallor of the optic disc results from ? color?

the loss of nerve fibers and a piling up of reflective astrocytes on top of the disc. As a result, the disc appears white.

The diagnosis of optic atrophy is based on (2)

the presence of disc pallor and decreased visual acuity.

Glaucomatous cupping results when

there is an increased cup to disc ratio of more than 50% as a result of increased intraocular pressure.

Papilledema ( U vs B/L), acute vission loss, what will develop in slowly progressive, usuall symptoms?

usually affects both eyes. Acute visual loss does not occur except for enlargement of the anatomic blind spot. Constriction of the visual fields may develop in slowly progressive papilledema. Most have no symptoms referable to the disc edema.

Pathologic aniscoria

≥0.5 mm difference in bright light >1 mm difference in dim light Relative size difference varies

Macula - location degeneration cause?

Macula is 2 discs temporal to optic disc • Macular degeneration -causes central visual loss

Papilledema vs optic neuritis Sim (1) differences ( 5)

- Both produces disc swelling. optic neuritis usually causes: 1- unilateral ocular pain with eye movement, 2- acute loss of central vision, 3- afferent pupillary defect in the involved eye. 4- Most patients with optic neuritis are young females 5- gradual recovery is the norm.

Myopia - legth of eye, far/near sight, lenth, correct with lense ( shape / power

- eye too long - near sightness ( can't see far) - lense with longer focal length - correct with concave, diverging, - power

Hyperopia - legth of eye, far/near sight, lenth, correct with lense ( shape / power

- eye too short - far sightness ( can't read) - lense with shorter focal length - correct with Convex, converging, + power

Anisometropia

-different focusing power between the two eyes

Emmetropia

-eye is refracting normally

Ametropia

-presence of refractive error

Types of cataract (3)

1- Nuclear 2-Posterior subcapsular 3- Cortical

Causes of oval pupil (3)

1- evolving third nerve palsy from brain herniation 2- previous surgery or trauma to the iris. 3- Adie's tonic pupil

The 3 components of the accommodation reaction? innervation?

1- ocular convergence, 2- pupillary constriction 3- thickening of the lens due to contraction of the ciliary muscles All mediated by the 3rd CN

Causes of papilledema ( 3)

1- retardation of axoplasmic flow at the level of the lamina cribrosa as a result of increased intracranial pressure. 2- axoplasmic swelling that causes "edema" of the disc. 3- occlusion of capillaries and venules that leads to the presence of hemorrhages and edema in between axons

Diabetic pupillary abnormalities inlude (2) and why

1- small pupils that fail to dilate normally in darkness due to sympathetic denervation 2- Sluggish constriction to bright light due to parasympathetic denervation

The normal pupillary response has two components:

1. A direct reflex where the illuminated pupil constricts; 2. A consensual reflex where the non-illuminated pupil constricts since input from one eye synapses with both ipsilateral and contralateral CN III.

anterior ischemic optic neuropathy due to? sympt presentation? occure in which pt group 5% associated with

AION is caused by 1- decreased blood flow to the optic disc through the posterior ciliary arteries. 2- sudden, painless, monocular blindness and optic disc swelling. 3- Most cases occur in diabetics and hypertensives. 4- 5% of cases are due to temporal arteritis in patients older than 60 years

Amblyopia - prevention

Amblyopia can be prevented if strabismus detected and treated before 5 years of age Some benefit if treatment begins between 5 and 14

disk size ( horizonal vs vertical) Large vs small disk size ( other names)

Average horizontal size: 1.77 mm Average vertical size: 1.88 mm

BC acuity: legal blindness, read with magnification,

BC acuity < 20/80 can drive • BC acuity 20/80 -20/160 can read with magnification • BC acuity 20/200 is legal blindness • BC acuity 20/200 -20/400 can move about normally

papilledema symptoms (3)

Binocular disc edema without eye pain Normal central visual acuity until well advanced Normal pupillary reflexes

Argyll-Robertson pupils Associated with? Location?

CNS syphilis. It may also occur in multiple sclerosis, sarcoidosis, diabetes mellitus, Lyme disease and following head trauma. The lesion responsible is believed to occur in the dorsal midbrain

Cataracts & afferent pupillary defect

Cataracts do not usually produce an afferent pupillary defect because the retina in the eye with the cataract compensates for diminished brightness much as it does in dim light

Refractive amblyopia

Causes amblyopia in the absence of ocular misalignment. It develops whenever there is a marked difference in the refractive error between the two eyes early in childhood. Cortical connections from the eye with the greatest refractive error are suppressed Amblyopia occurs if not corrected by age 5 Variable results if corrected between 5 and 14

can penetrate the retina at the optic disc and supply the retinal nerve layers in 1/3rd of normal people

Cilioretinal arteriole

Strabismus Comitant vs Non Comitant

Comitant Angle of eye misalignment constant in all directions of gaze Typical of developmental strabismus Noncomitant Angle of eye misalignment varies with direction of gaze Characteristic of acquired strabismus

Amylopia? causes (3)

Cortical unresponsiveness to visual stimuli Three causes Eye misalignment -strabismic Anisometropia -refractive Ocular opacities -occlusive

Amblyopia

Cortical unresponsiveness to visual stimuli - Unilateral defective vision, not correctable with glasses. The defective eye should read two or more lines poorer on an eye chart than the other eye

what develop as papilledema worsens (2)

Flame-shaped hemorrhages and soft exudates

6th cranial nerve (CN) paralysis causes ? due to? (2) - how?

Horizontal diplopia Inward turning during forward gaze Unable to turn eye laterally Increased ICP, ischemia (DM or HTN), tumor Diabetes causes microthrombi to develop in the vasa vasorum supplying the 6th CN. The microthrombi then cause a 6th CN infarction

Hirschberg corneal reflection test

Identifies tropia in children <6 months old

How does papilledema develop?

Increased ICP compresses central retinal vein in center of optic nerve. Congested retinal veins and capillaries dilate and bleed.

Optic disc edema Causes (3 I's)

Increased intracranial pressure • Inflammation of the optic nerve • Ischemia of the optic nerve

Cortical cataracts - location, risk factors (2) presentation?

Occurs in periphery of cortex Smoking and excessive UV light Central vision is preserved until late Patients initially have increased far vision but gradually lose near and far vision

Variable ptosis or diplopia that worsens as the day progresses and improves after the patient naps or rests may be a sign of? how can you make it more noticable?

Ocular myasthenia gravis. Ptosis will often become more noticeable by having the patient maintain upward gaze

Pigmented crescents ( normal or abn finding) , found in?

Pigmented crescents may be seen normally around the lateral margins of the disc particularly in myopic patients

Distance visual acuity testing - how to report it

Report patient'sacuity over standard acuity (20/80) Patient sees at 20 ft what a person with standard acuity sees at 80 ft If acuity worse than 20/40, test with pinhole to rule out amblyopia

Catarax risks (3)

Risk factors -cigarette smoking, diabetes, UV light

name of the eye card

Rosenbaum card for near visual acuity testing

Anisocoria - % in normal ppl difference in mm in normal or pathologic condition - due to?

Roughly 20% have normal physiologic anisocoria >0.4 mm in dim light. - difference is constant and doesn't change with light - inequality of 0.5 mm in bright light or >1 mm in dim light is pathologic - Pathologic anisocoria occurs when there is asymmetric disease of the iris, 3rd cranial nerve or sympathetic nerves.

The optic disc should be evaluated for (4)

Size and shape Cup to disc ratio Color Clarity of margins

anisocoria that increases in the dark indicates sym/parapathetic denervation of the dilator muscles.

Sympathetic

--- innervate the superior tarsal muscles that contribute to tonic elevation of the upper eyelid.

Sympathetic nerves

The panoptic ophthalmoscope vs direct ( magnification vs field of view)

The panoptic ophthalmoscope provides less magnification but a 5X larger field of view (25 degrees) than the traditional direct ophthalmoscope.

The size of the disc in hyperopic vs myopia

The size of the disc is smaller in hyperopic patients and the optic cup may appear to be non-existent. Myopia is larger than normal and the cup may appear to be more prominent.

Constant downward deviation of the eyes in infants may indicate ?

increased intracranial pressure and necessitates immediate neurologic evaluation,

hippus

Under steady illumination, the normal pupil continually dilates and constricts small amounts. This motion is termed hippus

Adie's (tonic) pupil ? shape? when noticable? cause?

Unilateral dilated pupil that constricts to near vision but poorly or not at all to light. - oval in appearance. - noticable once pt is unable to focus on near objects in the involved eye. - results from an isolated injury to the ciliary ganglion.

Cover /cross-cover test

Used in patients older than 6 months of age Detects tropias and phorias

afferent pupillary defect or Marcus Gunn pupil

When asymmetric retinal disease or optic nerve disease is present, the test produces a discrepant reaction to light between the two pupil

A 3rd CN lesion that affects extraocular muscle function, causes ptosis, but spares the pupil is most commonly due to? symp? (2)

a microinfarct in the vasa vasorum due to diabetes mellitus or hypertension. The patient frequently complains of eye pain or retro-orbital headache along with the abnormal physical exam findings.

Monocular diplopia is caused by

an abnormality of the lens or cornea in one eye and is not alleviated by covering the other eye

An efferent pupillary defect is caused by?

by impaired parasympathetic motor innervation to the pupillary sphincter. Direct pupillary response of the involved eye is diminished, but the consensual response of the non-involved eye is normal. The direct response of the non-involved eye is normal but the consensual response of the involved eye is diminished.

astigmatism - due to? corrected by?

can coexist with myopia and hypermetropia. The curvature of the cornea is ovular and several focal planes coexist at once. This causes blurred vision at multiple distances. Astigmatism is corrected with a cylindrical lens.

which artery support the retina

central retinal a ( from the ophthalmic a)

The photoreceptors are nourished by diffusion from the

choroidal circulation

Grave Dz & lymphatics

decrease lymph drainage due to local obstruction

Anisometropia

describes the situation where a patient's two eyes have markedly different refractive errors.

A 3rd cranial nerve lesion that affects the pupil, eyelid and extraocular muscles is usually caused by

extrinsic compression of the 3rd CN by an aneurysm of the posterior communicating artery or the basilar artery

Diplopia due to a cranial nerve lesion is most severe when the patient looks

in the direction that would be mediated by the injured cranial nerve.