Ocular Emergencies and Urgencies
Sudden Vision Loss
Anastas F. Pass
ICD-9: 362.34—TRANSIENT ARTERIAL OCCLUSION—AMAUROSIS FUGAX
ICD-9: 368.10—VISION DISTURBANCE; TRANSIENT VISUAL OBSCURATION
ICD-9: 368.11—SUDDEN VISUAL LOSS
ICD-9: 368.12—TRANSIENT VISUAL LOSS
THE DISEASE
Pathophysiology
Sudden vision loss may indicate a serious vascular disorder and, as such, should be recognized as an ocular emergency. Reduced blood flow and, hence, reduced levels of oxygen at the cellular level result in metabolic compromise. The loss in function may be permanent or temporary. Longstanding vision loss may not be recoverable and may be a precursor to cerebrovascular accidents. The spectrum of sudden vision loss includes local and benign causes (e.g., retinal migraine or acephalgic migraine) (Table 13-1); however, these are considered diagnoses of exclusion. Vascular anomalies that give rise to vision loss are not only sight threatening but may be life threatening as well. When discussing vision loss, transient or otherwise, it should be remembered that there are various categories of vision loss with specific diagnostic coding.
Transient visual obscuration—not a complete loss of vision but a “whiteout” or “grey-out” of vision. Most common with presence of papilledema or increased intracranial hypertension and lasts seconds to minutes.
Amaurosis fugax (AF)—a very brief loss of vision (typically unilateral) of seconds to minutes
Transient vision loss (TVL)—a loss of vision (unilateral or bilateral) of minutes to longer
Etiology
Vision loss, when it is acute and transient (AF or TVL) should be considered secondary to a vascular disorder until proved otherwise. Retinovascular and/or cerebrovascular accidents may be caused by emboli that can occlude the retinal arterial supply (twig, branch, or central) or the cerebrovascular circulation (carotid or vertebral-basilar [VB]). These occlusions may be transient, causing little or no retinal damage, or may result in long-standing retinal nonperfusion and permanent sight loss.
Blood dyscrasias, hyperlipidemia, hyperviscosity syndromes, sickle cell disease, syphilis, systemic hypertension, idiopathic intracranial hypertension, diabetes, and inflammatory conditions (e.g., giant cell arteritis [GCA; arteritic ischemic optic neuropathy], nonarteritic ischemic optic neuropathy, and optic neuritis) can also lead to occlusion of the arterial system. The same diseases may also produce optic nerve head edema, resulting in vision loss. Connective tissue diseases and the vasculitidies (GCA, polyarteritis nodosa, Takayasu’s arteritis) have also been implicated in vision loss. Arteritic ischemic optic neuropathy typically presents as a painful vision loss and should also be considered a medical emergency (see “Temporal Arteritis” in Chapter 19).
TABLE 13-1 Clinical Differentiation of Common Etiologies Involving TVL | |||||||||||||||||||||||||||||||||||
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Other etiological considerations include Uhtoff’s phenomenon (associated with MS or Leber’s optic neuropathy), branch retinal vein occlusion (BRVO)/central retinal vein occlusion (CRVO), venous stasis retinopathy, papillophlebitis, vasospastic AF, recurrent hyphema, orbital tumors, ocular ischemic syndrome, hypoperfusion, or dominant optic atrophy (now recognized as the most common heredodegenerative optic neuropathy).
Local causes, such as disc drusen, retinal detachment, and/or maculopathies, may result in sudden vision loss (or vision obscurations). Other considerations, as diagnoses of exclusion, include migrainous (scintillating) vision loss, drug toxicities, acute angle-closure glaucoma, or compressive lesions of the visual pathway.
The Patient
Symptoms and signs will vary depending on the circulatory system involved. Listed below are classic findings involving the retinal (R), carotid (C), and VB arteries, as well as inflammatory (I) causes.
Causes—Clinical Symptoms
R/C/VB—Decreased vision, visual field defects or vision loss (complete or incomplete); typically unilateral
R—Flashing lights
C—Hemisensory loss
C/VB—Diplopia
C/VB—Dysphasia
VB—Loss of equilibrium (ataxia)
VB—Weakness of the extremities (hemiplegia)
I—Pain (head, scalp tenderness, neck, periorbital)
VB—Most likely bilateral involvement (visual, motor, cerebellar)
Clinical Signs
Prominent Signs
Decreased acuity; typically unilateral (bilateral vision loss is an uncommon occurrence). With presentation of bilateral vision loss, one should assume a VB vascular anomaly (compression, embolus, occlusion), space occupying lesions, or a migrainous event; the latter on an exclusionary basis.
Retinal emboli may be visible and can be broken down into three main categories:
Fibrin-platelet—which originate in the heart, large vessels, or from a thrombus. This form of embolus rarely results in retinal infarction.
Cholesterol “Hollenhorst” plaque—which typically originate from a plaque forming at the carotid bifurcation
Calcific—which originate from cardiac valves and associated with rheumatic heart disease. This form of embolus will result in the most severe retinal infarction.
“Boxcarring” of blood flow (hyperviscosity syndromes)
Retinal nonperfusion and edema (as in artery occlusion)
Vein occlusion
Tortuous vasculature
Retinal arteriolar narrowing, focal constrictions, venous nicking
Subtle Signs
Possible relative afferent pupillary defect
Disc elevation/edema
Nerve fiber layer infarct(s)
Sensorium changes
Horner’s pupil (possible in long standing atherosclerosis and carotid dissection)
Demographics
By radiographic studies, 56% to 100% of patients with central retinal artery occlusion (CRAO) demonstrate carotid occlusive disease. Individuals >40 years old demonstrate the highest incidence of CRAO. The mean presentation is in the sixth decade of life.
Men have a higher incidence of CRAO, retinal occlusive disease, and TVL (associated with atherosclerotic
plaques) than do women; however, the incidence in postmenopausal women is equal to that of men. Life expectancy of patients with CRAO is 5.5 years, compared to 15.4 years for an agematched population without CRAO.
plaques) than do women; however, the incidence in postmenopausal women is equal to that of men. Life expectancy of patients with CRAO is 5.5 years, compared to 15.4 years for an agematched population without CRAO.
Individuals with retinal infarcts and emboli have a risk of stroke of 3% per year. Patients with TVL have a risk of stroke of 2% per year. (By comparison, patients without carotid artery disease [atherosclerosis] have a risk rate of 0.1% per year.) (See Table 13-2.)
Patients who report episodes of TVL have a high incidence of hyperlipidemia (60%) as well as ischemic heart disease (25%). The National Institute of Neurological Disorders and Stroke reports that approximately one third of individuals who experience a TVL will experience an acute stroke in the “near” future.
Incidence of retinal vascular occlusion is rare in children and young adults; however, the presence of TVLs and/or retinal occlusive disease in this group should be suspect for mitral valve prolapse, rheumatic heart disease, systemic lupus erythematosus, migrainous events, and recurrent hyphema. In patients younger than 40 years, an embolus from the heart is the most common cause of (central) retinal arterial occlusion. There is also suspicion that the use of oral contraceptives may cause TVLs in susceptible patients.
TABLE 13-2 Stroke Risk | ||||||||||||||
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Significant History
Previous report of a transient ischemic attack or stroke
Long-standing atherosclerosis
Long-standing arteriolarsclerosis
Cardiovascular anomalies (mitral valve prolapse, prosthetic valves, vasculitis, polycythemia, thrombocytosis)
Systemic hypertension
Diabetes mellitus
Dyslipidemia
Family history of transient ischemic attacks or vascular occlusive disease
Oral contraceptives
Smoking
Ancillary Tests
Ocular assessment for TVL would include best visual acuity, pupil assessment, dilated fundus examination, and visual field assessment
Laboratory studies: erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, complete blood count (CBC) with differential, platelet count, lipid profile, antinuclear antibodies (ANA), anticardiolipin, antiphospholipid antibody, and lupus anticoagulant
Noninvasive testing: blood pressure, carotid auscultation, cardiac evaluation (electrocardiogram, Holter monitor, echocardiogram), carotid duplex ultrasound, brain CT/MRI (consider magnetic resonance angiography [MRA] as a noninvasive carotid arterial evaluation), ophthalmodynamometry, or oculoplethysmography (for ocular perfusion pressures)
Invasive testing: IV retinal flourescein angiography may show the presence of embolic particles in areas of vessel leakage. Carotid angiography should be limited to those patients who will undergo carotid surgery (with >90% stenosis).
The Treatment
Transient Vision Loss
No immediate treatment is typically warranted; however, identifying the
underlying mechanism will determine the appropriate mode of therapy. A CBC with platelets, sedimentation rate (ESR) and CRP should be ordered immediately in every elderly patient to exclude a diagnosis of GCA even if pain is not reported. A combination of ESR and CRP gives the best specificity (98%) in detection of GCA. If GCA is suspected, high-dose steroids (i.e., prednisone 80 to 100 mg orally every day) should be initiated and a temporal artery biopsy should be performed, preferably within 1 week. IV methylprednisolone is also used to treat GCA. If GCA is confirmed, the patient will be on a maintenance dose of prednisone (5 to 7 mg orally every day).
Treatment is often limited to prevention, as with cardiac or carotid disease. Prophylactic initiation of an antiplatelet agent (e.g., aspirin 80 mg orally every day), other nonsteroidal anti-inflammatory drugs (NSAIDs), calcium channel blockers, or ticlopidine have been suggested.
As harmless as aspirin appears, it has several precautions. Aspirin is contraindicated in patients with asthma, hemophilia, preexisting hypoprothrombinemia, vitamin K deficiency, renal or hepatic dysfunction, patients receiving anticoagulants, and in third trimester pregnancy.
Aspirin plus dipyridamole (Aggrenox) has been suggested to be of increased effectiveness; however, there are increased risks, which make this treatment subject to study.
In profound carotid occlusive disease, surgical intervention may be warranted.
Patients who smoke cigarettes, particularly women who also take birth control pills, are at increased risk for stroke and cessation of smoking is essential.
Acute Angle-Closure Glaucoma
G. Richard Bennett
Fiaz Zaman
ICD-9: 365.22
THE DISEASE
Pathophysiology
Acute angle-closure glaucoma is characterized by a rapid and large increase in the intraocular pressure (IOP), resulting from a sudden blockage of the anterior chamber angle.
Etiology
Angle closure can be precipitated by several different mechanisms. The most common cause is pupillary block. A resistance to flow of aqueous humor develops between the iris and lens that causes pressure to increase in the posterior chamber. This resistance causes the peripheral iris to bow forward, which obstructs the anterior chamber angle and causes the IOP to rise rapidly. Conditions and medications that place the pupil in a mid-dilated position (i.e., mydriatics to dilate the pupil, dim illumination, and/or anticholinergics such as antihistamines or antipsychotics) maximize lens/iris touch and can precipitate pupillary block in patients with a narrow anterior chamber angle. Acute angle closure is more common in patients who are hyperopic because of decreased axial length and a compressed lens-iris diaphragm.
Acute angle closure can also occur because of plateau iris syndrome, in which the peripheral iris obstructs outflow without preexisting pupillary block (see section on “Plateau Iris”).
Secondary causes of acute angle closure include posterior synechiae formation (chronic inflammation or neovascular membranes) or anterior displacement of the lens-iris diaphragm (CRVOs, scleral buckles, extensive panretinal photocoagulation, posterior
segment tumors, choroidal detachments, or posterior misdirection syndrome).
segment tumors, choroidal detachments, or posterior misdirection syndrome).
The Patient
Clinical Symptoms
Symptoms on presentation include ocular pain, lacrimation, frontal headache, nausea, vomiting, photophobia, seeing colored halos around lights, and decreased vision. Patients can have a history of similar symptoms, suggesting prior episodes of intermittent angle closure.
Clinical Signs
Decreased vision
Conjunctival injection
Corneal microcystic edema
Shallow anterior chamber (deeper centrally than peripherally)
Mid-dilated pupil (pupil may be miotic if acute angle closure is secondary to posterior synechiae formation)
Significantly elevated IOP
Other signs that may be present include the following:
Glaukomflecken (anterior subcapsular lens opacities) are indicative of previous attacks
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