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History of the present illness
Functional visual loss- testing for visual acuity
- pupil examination
- confrontational visual field testing
- clinical clue table - painful red eye + visual loss
- clinical clue table differentiating optic nerve from visual pathway pathology
- treatment of central retinal artery occlusion
- treatment of acute angle-closure glaucoma
- treatment of retrobulbar hemorrhage
- substances causing toxic optic neuropathy
| Introduction |
- there are many pathological causes of sudden visual loss and the pathology either involves the eye itself, or the optic nerve or the neuro-visual pathways in the brain
- if the opthalmological examination is normal, it should still be possible to localize the probable site of the pathology by performing a careful visual acuity, pupillary reactivity and confrontational visual field examination
- this guidemap is designed to help a physician determine the probable cause of a loss of vision using pattern-recognition knowledge based on the known physiology/pathophysiology of the neuro-visual system, and there is a major emphasis on how best to detect acute pathological conditions causing sudden loss of vision
An emergency physician should always immediately seek, and expeditiously treat, vision-threatening disease in a patient presenting with loss of vision
- central retinal artery occlusion
- acute angle-closure glaucoma
- retro-orbital hemorrhage causing compressive optic neuropathy
| History of the present illness |
- the history should be focused on acquiring clinical clues as to the
likely cause of the visual loss
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| Examination |
The examination must be focused on:-
- identifying eye pathology, which can cause loss of vision, by examining the entire ocular media from the cornea to the retina
- identifying optic nerve disease
- identifying visual pathway disease
- visual acuity
- confrontational visual fields
- pupil reactivity
- ocular range of motion and any associated diploplia
- intra-ocular pressure prn
- then examine the external eye for any evidence of external eye disease causing loss of vision, starting at the outer eye
- first check the cornea and conjunctivae
- associated conjunctival "redness" is seen with keratitis, iritis, acute angle-closure glaucoma and orbital infections or cavernous sinus AV fistula
- chemosis suggests increased intra-ocular pressure secondary to intra-orbital or cavernous sinus pathology
- corneal defects or foreign bodies can affect vision if in the central visual axis
- clouding of the cornea with loss of corneal luster + a "fixed" mid-dilated pupil suggests angle-closure glaucoma
- the combination of subconjunctival hemorrhage + peri-orbital swelling + proptosis in a patient with a history of recent facial trauma suggests retro-bulbar hemorrhage as the possible cause of the visual loss (especially if the intra-ocular pressure is markedly elevated) => a low intra-ocular pressure suggests other possible causes of the visual loss eg. traumatic optic neuropathy, retinal detachment, globe rupture
- perform direct opthalmoscopy and first check for the red reflex by using the 10 diopter lens of a direct opthalmoscope held about 10 cm in front of the eye (defects in the red reflex can be due to lens opacities or vitreous floaters or intra-ocular foreign bodies)
- examine the anterior chamber and then the posterior chamber by using progressively less positive diopter lenses during the direct fundoscopic examination and look for flare and cells in the anterior chamber (iritis), then lens opacities/lens subluxation, then vitreous floaters/hemorrhages before finally focusing the opthalmoscope on the retina
- a vitreous hemorrhage is suggested by diffuse, dark particulate densities overlying the red fundus reflex (seen in diabetic retinopathy, retinal detachments, macular degeneration associated with neovascular formations)
(* a vitreous hemorrhage does not usually cause an afferent pupillary defect - suspect an associated large retinal detachment if an afferent pupillary defect is present => will require an ultrasound to make the diagnosis)
- examine the retina carefully for any retinal pathology, and specifically check the retina for eveness of retinal color, texture and congruity; check the retinal vessels for narrowing or attenuations or emboli; look for the presence of retinal hemorrhages or cotton wool spots or hard white/yellow spots and carefully examine the macular area for pathologic lesions or a "cherry-red" spot appearance
(* a detailed retinal exam is required if the patient has any visual loss and mandatory pupillary dilatation with mydriatic eyedrops eg. 0.5% tropicamide is necessary to perform an adequate retinal exam)
- carefully check the optic disc for swelling, change of color, and size/enlargement of the optic cup
- the optic disc becomes very pale (white) following optic atrophy
Optic atrophy
- note the pale white disc
(* it may take days/weeks for a damaged optic nerve to show signs of optic atrophy and optic atrophy is not seen in early optic nerve disease)
- optic atrophy implies pathology of the optic nerve or optic chiasm or optic tract, and is not seen in lesions affecting the more posterior neuro-visual pathways in the parietal or occipital cortex
- the optic disc has a characteristic "bow-tie" horizontal band of optic atrophy when the cause of the optic atrophy is in the optic chiasm or optic tract
"Bow-tie" optic atrophy
- note the white band of atrophy across the central section of the optic disc with preservation of the superior and inferior parts of the optic disc => resembling a "bow-tie"
- a swollen optic disc is usually unilateral and can be due to optic neuritis, anterior ischemic optic neuropathy or optic nerve compressive or infiltrative disorders
Optic disc swelling
(* optic disc swelling associated with choroidal folds/striae at the posterior pole +/- opto-ciliary shunt veins overlying the disc suggest distortion of the globe secondary to intra-orbital compressive pathology)
- a central retinal artery occlusion is suggested by a pale fundus with greying or whitening of the retina (ground-glass appearance) which may take 12 - 24 hours to develop, a cherry red spot on the macula, focal or diffuse retinal artery narrowing or attenuations, "box-car" segmentation of the retinal arteries or veins, visible emboli within the retinal vessels or an abrupt occlusion of a branch vessel (visual loss depends on the area/degree of ischemic retina)
Central retinal artery occlusion
- note the pale fundus
- note the cherry red spot at the macula
- note the diffuse arteriolar narrowing
- note the abrupt occlusion of the inferior nasal retinal artery branch
- a central retinal vein occlusion is suggested by retinal vein distension, retinal edema, retinal hemorrhages and exudates ("blood-and-thunder" fundus) – which may be focal with a branch occlusion or diffuse with a central vein occlusion
Central retinal vein occlusion
- a retinal detachment is suggested by bulging retinal folds, retinal arterioles/venules having an undulating snake-like appearance, visible retinal "holes" or horseshoe-shaped peripheral tears, "floaters" due to vitreous blood or pigment, a retina that appears grey and elevated or at different diopter levels on fundoscopy
Retinal detachment
- note that only part of the fundus is in focus
- note the billowing appearance of the detached retina
- retinitis (CMV, toxoplasmosis, histoplasmosis) is suggested by retinal edema and focal/disseminated retinal hemorrhages and white spots/patches
CMV retinitis
- an anterior ischemic optic neuropathy (AION) is suggested by an edematous pale optic disc +/- splinter hemorrhages on and around the disc + a normal retina
AION
(* the contra-lateral unaffected eye will usually show a small optic disc and small/absent optic cup, which is a major risk factor for AOIN => the absence of a small optic disc/cup in the uninvolved eye should strongly suggest an AION secondary to giant cell arteritis)
- neuroretinitis (inflammatory involvement of the intraocular optic nerve and associated peripapillary retina) is suggested by a massively swollen disc, retinal edema extending to the macula and yellowish lipid deposits around the macula causing a macular star appearance +/- retinal exudates and hemorrhages
Neuroretinitis with macular star
- macular degeneration is suggested by discrete yellow-white spots +/- areas of neo-vascularization +/- sub-retinal hemorrhages +/- vitreous hemorrhages +/- retinal detachments
- examine the superficial temporal arteries for tenderness and absent pulsations if ischemic optic neuropathy or central retinal artery occlusion is present
- carefully examine cranial nerves 3, 4, 5 and 6 to rule-out pathology in the orbit, or peri-chiasmal area, if an optic nerve or chiasmal lesion is suspected
- carefully perform a complete neurological examination in all patients with a homonymous hemianopsia, neurological symptoms, or if you supect a cerebral arteritis or multiple emboli
- perform a thorough examination of the heart and carotid artery if central retinal artery occlusion is found to look for a source of emboli
(* carotid artery plaque emboli are the commonest cause of CRAO in an elderly patient)
| Medical decision-making |
An emergency physician should first treat any immediate vision-threatening eye pathology found on ophthalmological examination eg. central retinal artery occlusion, acute narrow angle glaucoma, or retro-orbital hemorrhage associated with increased intra-ocular pressure + loss of vision
If no immediate vision-threatening eye pathology is found, then the emergency physician should appropriately triage and manage any other eye pathology discovered during the eye exam
- early therapy (within < 2 hours) is required to save vision in a patient with central retinal artery occlusion, but therapy should not be witheld even if > 6 - 12 hours have elapsed
(* see the appendix for details regarding the immediate treatment of central retinal artery occlusion)
- in young patients with central retinal artery occlusion => suspect cardiac emboli from diseased valves or an atrial myxoma, IV drug abuse and secondary endocarditis or talc emboli, vasculitis, sickle cell disease, hypercoagulable states, vasospasm secondary to migraine or Raynauds disease
- in elderly patients with central retinal artery occlusion => suspect giant cell (temporal) arteritis, thrombotic occlusion in situ or embolic occlusion from cholesterol (Hallenhorst) plaques, platelet-fibrin emboli from the carotid artery or hypotension-induced ischemia, hyperviscosity syndromes
- there is no effective acute treatment for central retinal vein occlusion, but the patient should have a workup to exclude diabetes, hypertension, arteriosclerosis, hyperviscosity syndromes, coagulopathies, compressive syndromes and glaucoma
(* hyperviscosity syndromes are the exception to the rule and immediate therapy may improve the outcome)
- a patient with a suspected retinal detachment requires emergent opthalmological consultation, especially if the detachment threatens the macula => immediate therapy may be required to avert irreversible visual loss
- a patient with acute angle-closure glaucoma requires immediate therapy to decrease the intra-ocular pressure
(* see the appendix for details about the therapy of acute angle closure glaucoma)
- consult an ophthalmologist if a patient presents with a vitreous hemorrhage, especially if you suspect an associated retinal detachment => further workup and admission may be indicated
- consult an ophthalmologist for patients with a maculopathy or choroidio-retinitis or retinitis
- retinitis in a HIV patient requires a medical specialist's work-up (wide differential diagnosis including CMV, toxoplasmosis, herpes, fungal, granulomatous or hematogenous disease)
- neuroretinitis is usually benign => non-emergent referral to an ophthalmologist
If the diagnosis is not immediately obvious because of the apparent absence of overt external eye or internal eye pathology => try and determine whether the pathology lies in the optic nerve or the visual pathways posterior to the optic chiasm
- differentiation between optic nerve (pre-chiasmal) pathology and visual pathway (chiasmal and post-chiasmal) pathology is critically dependent on a very accurate assessment of any visual field defects + presence/absence of an afferent pupillary defect
Monocular visual loss not respecting the vertical meridian + afferent pupillary defect => optic nerve pathology
Bilteral visual loss respecting the vertical meridian + afferent pupillary defect => visual pathway pathology anterior to the optic tract
Bilteral visual loss respecting the vertical meridian + absent afferent pupillary defect => visual pathway pathology posterior to the optic tract
- chiasmal and post-chiasmal visual pathway disease nearly always produces a visual field defect that respects the vertical meridian
If an emergency physician cannot precisely map-out a visual field defect using confrontational visual field testing, he should at least attempt to demonstrate that there is a bilateral visual field defect, which respects the vertical meridian, and that is either bitemporal or homonymous => any suggestion of visual pathway pathology warrants neurological consultation + diagnostic neuro-imaging
An emergency physician can attempt to make a precise topographical diagnosis of visual pathway disease using the following information - if time and interest permits
Visual pathway anatomy
1 = central scotoma secondary to optic neuritis (does not respect
the vertical meridian)
2 = Total blindness of the right eye from a complete lesion
of the optic nerve
3 = Bitemporal hemianopia from a complete lesion of the optic
chiasm
4 = Right nasal hemianopia from a perichiasmal lesion
5 = Right homonymous hemianopia from a complete left optic tract
lesion
6 = Right homonymous superior quadrantopia caused by partial
involvement of the optic radiation in the left temporal lobe (Meyer's loop)
7 = Right homonymous inferior quadrantopia caused by partial
involvement of the optic radiation in the left parietal lobe
8 = Right homonymous hemianopia from a complete lesion of the
left optic radiation
9 = Right homonymous hemianopia (with macular sparing) from
a posterior cerebral artery occlusion causing ischemia of the calcarine
cortex of the occipital lobe
- a homonymous visual field defect that respects the vertical meridian (the visual field defect starts abruptly at the vertical midline) + normal visual acuity + no afferent pupillary defect => localises the pathology to the visual pathway posterior to the optic chiasm/tract (post-geniculate lesions)
(* pre-geniculate lesions involving the optic tract may affect central visual acuity, cause an afferent pupillary defect and cause optic atrophy)
- the degree of congruity of the homonymous hemianopia usually increases the further back along the post-chiasmal visual pathway the pathology resides
(* an optic tract lesion usually produces a very incongruous homonymous hemianopia - the shape of the visual field defect is very different in the two half fields and the defect is variably dense with sloping sides; post-geniculate lesions produce an incongruous homonymous hemianopia with greater density and steep sides)
- if the homonymous hemianopia is complete => it is difficult to precisely localize the site of the pathology => use the pattern of associated neurological signs or neuroimaging to precisely localize the exact site of the pathology
- if the homonymous hemianopia is isolated (no other neurological abnormalities) => the occipital lobe is usually the site of the pathology in 90% of cases, and vascular causes account for about 50 - 75% of those cases
- an optic tract lesion usually produces an incongruous, incomplete homonymous hemianopia (example 5 in the diagram)
(* an optic tract lesion may also produce a contra-lateral afferent pupillary defect if the homonymous hemianopia is complete - although the patient has normal visual acuity + normal color vision + no sensation of reduced light sensation)
- a lesion in the lateral geniculate body may cause a contra-lateral congruous or incongruous homonymous hemianopia
(* specific patterns that suggest a focal lateral geniculate body infarct include a congruous homonymous horizontal sectoranopia secondary to lateral choroidal artery ischemia, or a congruous homonymous quadruple sectoranopia secondary to anterior choroidal artery ischemia)
- an incomplete lesion in the temporal loop of the optic radiation produces a contra-lateral congruous/incongruous partial or complete homonymous superior quadrantopia (example 6 in the diagram)
(* a wedge-shaped defect in the upper visual field is often called a "pie-in-the-sky" defect to emphasize its wedge shaped appearance and superior location)
- a lesion in the antero-superior parietal lobe projection of the optic radiation produces a contra-lateral congruous, partial or complete homonymous inferior quadrantopia (example 7 in the diagram)
(* this localised pathology is very rare and most parietal lesions produce a complete homonymous hemianopia affecting both the superior and the inferior visual fields)
- a complete parieto-occipital interruption of the optic radiation produces a complete congruous homonymous hemianopia often sparing central vision (example 8 in the diagram)
(* the patient may also have a disturbance of the fixation reflex causing an associated ipsilateral smooth pursuit defect when the moving object is moved toward the side of the lesion, visual neglect, visual agnosia and spasticity of conjugate gaze – the eyes may deviate superiorly and away from the side of the lesion during eye closure, rather than the normal Bell's phenomenon in which each eye deviates superio-laterally)
- lesions in the occipital cortex produce very congruous, contra-lateral homonymous scotomas, or very congruous homonymous inferior or superior altitudinal defects with/without macular sparing - although the defects may be incomplete on the one side (and the degree of macular sparing may also vary on that side)
- the homonymous defects may encroach at least acutely on central vision, although the macula is usually spared => allowing normal visual acuity in the central axis (example 9 in the diagram)
(* the peripheral visual fields are represented in the anterior part of the calcarine cortex - an area supplied by the posterior occipital artery - so an infarct secondary to occlusion of the posterior cerebral artery causes "tunnel vision" and spares the macula, which is represented in an area of the posterior calcarine cortex, which also receives blood supply from the middle cerebral artery)
- lesions of the tip of the occipital lobe produce small central homonymous scotomas that are exquisitely congrous, but usually spare the macula
(* another clue to an occipital lesion is static-kinetic dissociation with relative preservation of vision in the hemianopic field when kinetic stimuli are presented, as opposed to stationary stimuli = Riddoch phenomenon)
- cortical blindness exists when bilateral occipital lobe damage is extensive causing a complete bilateral homonymous hemianopia involving the periphery and the macula => the patient is totally blind with normal pupillary responses and a negative RAPD
(* Anton's syndrome = anosognosia = bilateral cortical blindness associated with a denial of blindness, because the damage is so extensive that it also affects the visual association areas)
- associated neurological signs also help localize the probable site of the post-chiasmal pathology
- homonymous hemianopia + contralateral hemiparesis + hypothalamic signs (pain of central origin localized to the contra-lateral body) => optic tract or lateral geniculate body lesion
- homonymous hemianopia + difficulty memorizing spoken words +/- severe language disturbance => dominant temporal lobe optic radiation lesion
- homonymous hemianopia + auditory agnosia => non-dominant temporal lobe optic radiation lesion
(* complex partial seizures and /or formed-type visual hallucinations in the affected homonymous visual field are seen in dominant and non-dominant temporal lobe lesions)
- homonymous hemianopia + hemiparesis + hemisensory loss + aphasia (or apraxia or agnosia or acalculia or apgraphia) => optic radiation lesion in the dominant parietal lobe
- homonymous hemianopia + impaired construction ability, dyscalculia and hemi-neglect => optic radiation lesion in the non-dominant parietal lobe
- isolated homonymous hemianopia with no other neurological abnormalities => occipital lesion (usually ischemic infarct)
(* All patients with a homonymous hemianopia require a neurological consulation and neurological imaging)
- an optic chiasmal lesion usually produces a bitemporal hemianopia (example 3 in the diagram), but it may produce an incongruous defect if the lesion is situated alongside the anterior chiasm closer to the distal end of one of the optic nerves => may produce a central visual field defect in the ipsilateral eye suggestive of an optic nerve lesion and a small contralateral superior temporal visual field defect in the opposite "apparently normal" eye => so always carefully examine the superior temporal visual field of the "apparently normal" eye in any patient with unilateral visual loss of the optic nerve type (before incorrectly concluding that the patient has optic nerve pathology)
- sudden visual loss + incongruous bitemporal hemianopia => suggests pituatry apoplexy (hemorrhage into a suprasellar mass) or carotid artery aneurysm expansion causing compression of the optic chiasm
- subacute visual loss + incongruous bitemporal hemianopsia => suggests subacute chiasmal pathology (in order of frequency - pituatry adenoma, craniopharyngioma, meningioma, aneurysmal compression, glioma)
- suprasellar infrachiasmal lesion impinging on the optic chiasm from below (eg. pituatry adenoma) => upper outer quadrants affected first => superior bitemporal hemianopia (peripheral temporal fields also affected greater than paracentral temporal fields => visual field defects are denser peripherally); suprasellar suprachiasmal lesions impinging on the optic chiasm from above => inferior bitemporal visual field defects
- lesions that damage the posterior portion of the optic chiasm mainly affect the temporal area just alongside the macula => may produce bilateral temporal paracentral scotomas, which are often wrongly misinterpreted as resulting from a bilateral optic neuropathy
(* bitemporal hemianopic scotomas are nearly always associated with normal visual acuity and normal color perception, while patients with bilateral optic neuropathy have bilaterally impaired vision + abnormal color perception +/- bilaterally sluggish pupils)
- lesions that damage the posterior aspect of the optic chiasm may also damage one of the optic tracts producing additional signs of a homonymous field defect => complex visual field defects due to the combination of optic chiasm defects + optic tract defects
Axiom - whenever there is extension of a lesion from the optic chiasm to the adjacent optic nerve or optic tract, the blind (or near blind) eye is always on the side of extension of the lesion; also, whenever there is extension of a lesion from an optic nerve or optic tract to the optic chiasm, the blind (or near blind) eye is always on the side of the original pathology
- lesions impinging on the lateral optic chiasm may first produce an ipsilateral nasal hemianopia due to pressure on the uncrossed temporal nerve fibres from the ipsilateral eye (example 4 in the diagram) => extension of the lesion may eventually impinge on the crossed nasal fibres from the contralateral eye producing a grossly incongruous contralateral homonymous hemianopia (nasal defect >> temporal defect), which mimics an incomplete optic tract lesion (example 5 in the diagram)
(* incomplete optic tract lesions, due to medial compression, usually produce a temporal defect >> nasal defect, and the temporal defect is greater in the inferior field because the lower nasal fibres rotate away from the pressure, and the nasal defect is greater inferiorly because the lower temporal fibres, which are furthest away from compressive forces, are spared)
- a patient with significant bitemporal hemianopia may also have a disturbance of depth perception because the overlap of the two blind temporal visual fields on close vision may create a blind area with its apex at the point of fixation (patient may have difficulty threading needles or sewing)
Area of blindness on close vision
- a patient with bitemporal visual field defects may also complain of diploplia because of the loss of the normal partial overlap of the temporal field of one eye and nasal field of the other eye (hemifield slide phenomenon) => difficulty reading because of doubling or loss of printed letters or words
If the visual loss is monocular + no signs of internal or external eye pathology + afferent pupillary defect => suggests pre-chiasmal optic nerve pathology => consult an ophthalmologist
It time and interest permits, an emergency
physician should attempt to identify the likely etiology of the optic neuropathy
using the following information
- an ischemic optic neuropathy is suggested by reduced
visual acuity of sudden onset + dyschromatopsia (decreased color vision)
+ an afferent pupillary defect + central or paracentral or arcuate or inferior
altitudinal (commonest) or nasal step visual field defects +/- optic disc
swelling in a patient, who has normal ocular media + no retinal pathology
- ischemic optic neuropathy is the commonest cause of sudden optic nerve type visual loss in patients past middle age
- an ischemic optic neuropathy (ION) is presumed to be secondary to posterior ciliary artery thrombotic (non-embolic) occlusion and is classified as either anterior ischemic optic neuropathy (AION, which is more common and accounts for 90% of cases, and defined by the presence of optic disc swelling due to an infarct of the optic nerve at the lamina cribrosa level) or posterior ischemic optic neuropathy (PION, which is less common and accounts for 10% of cases, and which has no associated visible optic disc swelling because the pathology is retro-bulbar; PION is much more commonly associated with an associated arteritis eg. temporal arteritis)
- the optic disc in AION is swollen (and either pale or hyperemic), and flame shaped hemorrhages are often present near the disc margin +/- focal or general retinal arteriolar narrowing/attenuation (soft white exudates are very rare)
AION
- note the swollen optic disc
- note the peri-capillary splinter hemorrhages
(* note that it is not possible to differentiate the different pathological causes of optic disc swelling from the appearance of the fundus, and this photograph could be compatible with optic neuritis or papilledema or compressive optic neuropathy)
- although 95% cases of AOIN are non-arteritic and presumably due to non-arteritic thrombotic occlusion of the posterior ciliary artery, an acute ischemic optic neuropathy in a patient > 50 years of age => giant-cell (temporal) arteritis until proven otherwise - especially if the visual loss is profound and the contra-lateral optic cup is normal/large in size
- review the history for symptoms suggestive of giant-cell (temporal) arteritis + look for clinical signs of giant-cell (temporal) arteritis + perform a sed rate => suggestive history and/or clinical exam, or high sed rate in a patient > 50 years with a sudden optic neuropathy => start high dose IV steroids (1g methylprednisolone/day) + consult opthalmologist/internist
(* the sed rate may be normal in ~ 20% of patients with cerebral arteritis and does not exclude the disease)
- bilateral, non-arteritic AION occurring at the same time is very rare and the sudden onset of simultaneous bilateral optic neuropathy => giant-cell (temporal) arteritis until proven otherwise
- it is important to diagnose giant-cell arteritis because the second eye will become involved within hours-days in ~ 25 - 50% of cases if the patient is not treated with high dose steroids
(* temporal artery biopsies will likely remain positive even after 14 days of steroid therapy)
- if the patient with AION/PION does not have evidence of giant-cell arteritis => further workup includes excluding ischemic optic neuropathy associated with diabetes mellitus or hypertension or systemic vascular disease or profound anemia or ocular hypoperfusion syndrome or rarer causes (vasculitis or hyperviscosity syndromes)
- AION is rarely associated with carotid artery disease or cardiac-embolic disease, and non-invasive carotid artery studies, transcranial Doppler ultrasound studies and cardiac echocardiography studies are rarely indicated (in contrast to patients with central retinal artery occlusion, who require an extensive cardiac/carotid workup to look for a source of emboli)
- PION should only be diagnosed (if the patient does not have giant cell arteritis) after rigorous exclusion of a possible compressive, inflammatory or toxic optic neuropathy
- there is no effective treatment for non-arteritic ischemic optic neuropathy and rapid reduction of any uncontrolled hypertension may increase the degree of optic nerve ischemia and increase the visual loss
- the majority of patients, who develop AION in both eyes, do so non-simultaneously => the presently affected eye has optic disc swelling and the contra-lateral eye has optic atrophy from the previous episode of ION
(* the optic disc appearance(s) may mimic the Foster-Kennedy syndrome
= optic atrophy in one eye due to an intracranial mass compressing
one optic nerve and optic disc swelling in the other eye due to
papilledema from the secondary increased intracranial pressure - differentiation
is based on the fact that a patient with bilateral, sequential ION has
acute visual loss in the eye with the swollen optic disc + a history of
previous sudden loss of vision in the eye with optic atrophy, while patients
with the Foster-Kennedy syndrome have normal visual acuity in the eye with
a swollen optic disc and a history of subacute/chronic visual loss in the
eye with optic atrophy)
- optic neuritis is more common in younger patients (females
in their 20 - 40's) - the patients have retro-orbital pain on eye movements
(90% of patients), varying degrees of visual loss, varying shapes/sizes
of visual field defects of the optic nerve type, varying degrees of an
afferent pupillary defect and they very uncommonly have visible optic disc
swelling
(* young age and pain with eye movements are strong predictors that inflammation is the cause of the optic neuropathy)
- the majority of patients have a normal retina and optic disc - the "doctor sees nothing when the patient sees nothing" and it takes weeks for signs of optic atrophy (pale optic disc) to develop
- most patients with optic neuritis develop a central visual acuity impairment, which reaches its nadir over a week => then improves over the next several weeks (Uhthoff's symptom = episodic blurring of vision during the recovery period precipitated by exercise or a hot bath/hot weather) - although they may still complain that their vision is "not right" or that colors are "washed-out"
- some opthalmologists will treat patients with a diagnosis of optic neuritis secondary to presumptive demyelinating disease with IV steroids (250mg methylprednisolone qid x 3 days) in hospital - because the 1-year risk of of developing MS can be significantly reduced compared to po steroid treatment or no treatment, although there is apparently no difference in outcome after 3 years (consult an opthalmologist for his practice recommendation)
- rare causes of optic neuritis include syphilis, sarcoidosis, cat scratch disease, Lyme disease or lupus (or other vasculitidies) - further testing is usually only indicated if the associated clinical picture is very suggestive of these disorders, or if there is a macular star suggestive of neuroretinitis
(* further testing for causes of optic neuritis can be deferred to the opthalmologist)
- if the patient does not have a classic presentation of ischemic optic neuropathy or optic neuritis (or the visual loss has not improved within 7 - 14 days) => further investigations are required to exclude compressive optic neuropathy
(* a gadolinium-enhanced MRI of the brain and orbits => may show intra-orbital
compressive pathology or optic nerve lesions or 'enhancing lesions" of
the optic nerves and brain, which is found in many patients with multiple
sclerosis, or it may detect vasculitic or granulomatous or carcinomatous
infiltrative lesions of the optic nerve)
- a compressive optic neuropathy should be suspected
if a patient presents with a complaint of progressive dimming of vision
+ an afferent pupillary defect and/or decreased color perception (red objects
appear dark or dull or brown or faded) + an ocular fundus examination that
is either normal or shows optic disc swelling or optic atrophy; or if the
patient presents with unexplained optic disc swelling + no visual
complaints + no visual loss + no afferent pupillary defect
(* patients with a compressive optic neuropathy may have a variety of non-specific visual field defects that are non-diagnostic +/- proptosis)
- a sudden compressive optic neuropathy (pituatry apoplexy, ruptured opthalmic artery aneurysm, mucocele/pyocele of the paranasal sinuses) should be suspected when peri-orbital pain or a frontal headache accompanies the sudden visual loss
- a sudden compressive optic neuropathy + 3rd, 4th and 6th cranial nerve dysfunction localises the lesion to the superior orbital fissure or orbital apex, or cavernous sinus area
- a traumatic optic neuropathy may be anterior (within 10mm of the globe) and affect the central artery or vein => visual loss + fundal examination suggestive of central retinal artery or vein occlusion; or it may be posterior => visual loss + no immediate change in the appearance of the ocular fundus
(* a traumatic optic neuropathy is a clinical diagnosis that is typically made when sudden visual loss is temporally related to blunt or penetrating head or face trauma; and a diagnosis of traumatic optic neuropathy should not readily be made in the absence of an afferent pupillary defect on the side of the presumed injury)
- there is no well-defined approach to a traumatic optic neuropathy, which is not associated with a compressive intra-orbital process => consult an opthalmologist, who may elect to use high dose IV steroids (30mg/kg of methylprednisolone loading dose and 5.4 mg/kg/hour thereafter)
- a patient with a retro-bulbar hemorrhage + increased intra-ocular pressure + decreased visual acuity due to a compressive optic neuropathy requires emergent treatment
(* see the appendix for details of the emergency treatment of a retrobulbar hemorrhage causing increased intra-ocular pressure)
- an acute optic neuropathy + small retinal vessel occlusions +/- choroidal infarcts => vasculitis or endocarditis or hyperviscosity syndrome until proven otherwise
If there is no evidence of eye pathology, or objective evidence of optic nerve disease (no afferent pupillary defect + normally reactive pupils), or any apparent visual field defect => consider the possibility of functional visual loss
- a functional visual loss should be suspected when the patient, who claims to be totally blind (despite a negative RAPD + normal eye exam), cannot sign his name legibly and neatly, or oppose his index fingertips together in the midline in front of his face, and cannot suppress eye movements when a large mirror is held in front of his face and tilted back-and-forth or from side-to-side
Consult an opthalmologist, and arrange for the patient to have a specialist clinical evaluation, and do not label the patient as having a functional problem
| Appendix |
- visual acuity is the "vital sign" of the eye
- visual acuity testing should be carefully and accurately performed
- visual acuity is best tested with corrective lenses in place to eliminate the decreased vision due to chronic refractive errors
- if the patient's corrective lenses are not available => test visual acuity using a multiple pinhole device (the device eliminates the problem of refractive errors and visual impairment due to some localised lesions in the cornea, lens and vitreous chamber)
- a metal protective eyeshield with multiple small holes can be used if the special pinhole testing device is unavailable
- the visual acuity should be tested using a formal chart at 20 feet and recorded as the lowest line the patient can correctly read more than half the letters (the number of unread letters should be recorded as well eg. 20/40 – 2
- a dull or faded temporal letter on the visual chart implies a temporal visual field defect or paracentral scotoma, while difficulty viewing a central letter implies a central scotoma
- difficulty viewing the optotypes above or below the line of visual fixation suggests an altitudinal visual field defect or paracentral scotoma
- if the patient cannot read the first line (vision < 20/200) => move the patient forward until he can read the first line and record the distance from the chart eg. if the first line can be read at 8 feet => visual acuity = 8/200
- if the patient cannot read any letters => ask the patient to count fingers and record the distance from the face that fingers can be counted
- if the patient cannot count fingers => ask the patient if he can discern hand motion
- if the patient cannot discern hand motion => shine a light towards the patient's eye from each of the four quadrants (record the vision as "light perception with projection")
- if the patient cannot detect the direction of the shining light => ask the patient if he can discern any light sensation (record the vision as "light perception without projection" or "no light perception" )
- should be performed in a darkened room
- record the initial pupil size, the rate of reactivity to bright light and the final size of the pupil after shining a bright light into the eye for one second
- perform the swinging flashlight test if the pupils are equal in size, but one pupil has no/decreased reactivity to light to determine the presence of a relative afferent pupillary defect (RAPD)
- the swinging flashlight test is performed by shining a flashlight into one eye for two seconds and then switching to the other eye for two seconds and repeating this process about 2 - 3 X while looking for a direct pupillary response to the bright light
(* avoid excessive repeat testing => excessive exposure to bright light will bleach the photoreceptors and create a false-positive result)
- a RAPD (Marcus-Gunn pupil) is present when the affected pupil dilates (or doesn't constrict as much as the opposite pupil) when a bright light is shone into the pupil => implies an ipsilateral defect in optic nerve function (very rarely positive in extensive retinal disease)
- the swinging flashlight test is a very sensitive test of optic nerve function, but will be negative if both eyes have significant optic nerve dysfunction (both pupils become dilated and sluggish)
- the degree of RAPD is usually directly proportional to the amount of visual field loss, but more RAPD per line of visual acuity loss suggests optic nerve disease rather than macular disease
- poor acuity + poor color vision implies optic nerve disease , while poor visual acuity + good color vision implies retinal disease (patients with optic nerve disease also have a signficantly decreased sense of brightness)
Confrontational visual field testing
- an essential exam in all patients with a complaint of visual loss
- stand facing the patient with your face directly opposite the patient's face, at a distance of about 2 – 3 ' away from the patient
- ask the patient to continuously look at your nose => inquire whether he can see your nose and other facial features clearly
- inability to clearly see your nose => central scotoma
- inability to clearly see your eyes or lips => paracentral scotoma
- inability to clearly see your ears => peripheral visual field defect
- you can quickly check the vertical hemianopic line in a "wink-of-an-eye" by alternatively closing each eye and asking the patient if both eyes are open
- a more senstive test for central/paracentral scotomata is to use two red-topped mydriatic eyedrop bottles held in front of the examiner's face => ask the patient to compare the brightness of the red- topped mydriatic eyedrop bottles held in different areas of the visual field => a darkening/browning of the red color is a more sensitive test of optic nerve dysfunction than absent vision
(* color vision is especially important in the diagnosis of pre-geniculate pathway lesions - if a patient with significantly impaired visual acuity can still detect a red object => a pregeniculate nerve pathway lesion is unlikely; however many normal people may notice that a red object is duller in the temporal visual field and appreciably brighter in the nasal visual field)
- then test the visual fields in all four quadrants at about 30 degrees off the central axis (best performed by asking the patient to count your fingers held alongside your face above and below ear level)
(* don't test ultra-peripheral vision by holding the fingers off to the sides because all relevant visual field defects occur within 30 degrees of the central axis)
- if there is a suggestion of a visual field defect => move your fingers (or a red-topped mydriatic eyedrop bottle) from the sides towards the center in 30 degree increments, and from the center toward the sides, to try and semi-define the size and extent of the visual field defect
- a visual field defect that respects the vertical midline => implies a defect in the visual pathway situated at or posterior to the optic chiasm (optic chiasm => occipital lobe)
- if you detect a vertical hemianopia, try and determine whether it spares the macula (macular sparing) or splits the macula (macula splitting ) by carefully checking the transition line in the horizontal plane compared to spots about 15 - 30 degrees above and below the horizontal axis
- in post-geniculate lesions a steep-sided instant transition edge of the visual field defect will be found, while pre-geniculate lesions may produce a slope-sided transitional edge visual field defect
- optic nerve defects do not respect the vertical meridian and can be central, paracentral or altitudinal (respect the horizontal meridian)
- visual field defects in retinal disease occur if the retinal disease is extensive and the defects correspond inversely with the localisation of the retinal disease (eg. superior retinal pathology => inferior visual field defects)
(* the size of the defects depend on the area of retinal pathology and may be focal producing a "hole" in the visual field, or more extensive producing larger scotomata)
- visual field defects that only extend from the macula to the blind spot are called cecocentral scotoma and are usually due to vitamin B12 deficiency, toxins or glaucoma
(* glaucoma may first produce a superior arcuate defect extending fom the macula to the optic disc - secondary to compression of the inferior nerve fibre bundles at the edge of the optic disc - prior to producing a full-fledged cecocentral scotoma)
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| Disease | Clinical clue |
| Acute ischemic optic neuropathy |
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| Optic neuritis due to MS |
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| Compressive optic neuropathy |
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| Optic chiasm pathology |
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| Optic tract pathology |
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| Optic radiation pathology |
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| Occipital lobe pathology |
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Treatment of central retinal artery occlusion
1) Lay the patient flat
2) Massage the eye through the closed upper eyelid for 5 - 15 seconds => remove pressure for 15 seconds => repeat the process at least 5x
3) Acetazolamide - 500mg IV
4) Sublingual NTG 0.4 mg if the blood pressure is stable
5) Get the patient to breathe into a paper bag for 10 minutes each hour (or inhale carbogen gas - 5% carbon dioxide in 100% oxygen)
6) Timolol maleate (0.5%) eyedrops - one-to-two gtts topicallly
7) Emergent opthalmological consultation for anterior chamber paracentesis, selective opthalmic artery intra-arterial fibrinolytic therapy, or hyperbaric oxygen therapy
8) Heparin anticoagulation is used prophylactically for amaurosis fugax suggestive of impending central retinal artery occlusion
9) Workup to look for source of arterial emboli and/or exclude arteritic or hypercoagulable state
Treatment of acute angle-closure glaucoma
1) Pilocarpine 2 - 4 % eyedrops - one-two gtts q 15 minutes until pupillary constriction occurs
(* a 2% solution may be better in blue-eyed patients and a 4% solution in brown-eyed patients)
2) Timolol (Timoptic) 0.5% eyedrops - one-two gtts topically five minutes after instillation of the pilocarpine eyedrops
(* other beta blocker eyedrops can be used eg. betaxanolol - 0.5% (Betoptic) or levobunolol - 0.5% (Betagan)
3) Acetazolamide (Diamox) - 500mg IV (or po)
(* contra-indicated in sulfa allergic patients, metabolic acidosis or kidney disease)
4) Oral glycerine - 50% solution (Osmoglyn) = 1 - 2 g/kg (2 - 3cc/kg) in cold orange or lemon juice or
5) Oral isorbide - 45% solution (Ismotic) can be used instead of oral glycerine - 1.5 mg/kg mixed with orange or lemon juice and ice
6) Mannitol 20% solution = 5 - 10 ml/kg IV over 15 minutes (1 - 2 g/kg) if the patient is vomiting and cannot take oral osmotic agents
7) Early opthalmological consultation for definitive surgical therapy
8) Parenteral analgesics prn
(* see the excellent textbook chapter on " Angle closure glaucoma " in the online textbook of emergency medicine at emedicine.com)
Treatment of retro-bulbar hemorrhage associated with proptosis and decreased visual acuity
1) Immediate eye massage to reduce intra-orbital pressure by means of redistribution of extraocular fluid (if there is no signs of an open globe rupture)
2) Elevation of the head of the bed + sedation
3) Mannitol = 1 - 2g/kg over 15 minutes IV
3) Acetazolamide - 500mg IV
4) Lateral cathotomy with cantholysis is indicated if the intra-ocular pressure remains >50 mmHg
5) If the above procedures are not successful => immediate orbital imaging to look for pathology that may benefit from an orbital decompression procedure
Substances known or believed to cause toxic optic neuropathy
- amantidine hydrochloride - amiodarone
- arsenicals
- cafergot
- carbon tetrachloride
- chlorambucil
- chloramphenicol
- chlorpromazine
- chlorpropamide
- cisplatin
- clioquinol
- cyclosporine
- dapsone
- deferioxamine
- dinitrobenezene
- disulfuram
- emetine
- ergot
- ethambutol
- ethylchlorvynol
- ethylene glycol
- 5-fluorouracil
- hydroquinolines
- hexachlorophene
- interferon-alpha
- iodoform
- iodoquinol
- isonoazid
- lead
- methanol
- methyl bromide
- organic solvents
- penicillamine
- quinine
- streptomycin
- sulfonamides
- tamoxifen
- thallium
- tobacco
- toluene
- trichlorethylene
- vincristine
Disclaimer : My EM guidemaps reflect my personal approach to problem-solving/managing clinical cases in an ED setting and they should not be regarded as the standard of care. They merely represent the personal opinions of the author and they should only be used in clinical practice if the reader-user has substantial reason to believe that the clinical advice contained in the guidemaps is valid and accurate. The guidemaps are not meant to be "authoritative" and the reader-user should consult standard medical textbooks and expert opinion articles/guidelines for more authoritative advice. The reader-user should particularly confirm all drug doses, their indications and contra-indications, prior to their use.