INTRODUCTION	Section 2 of 10
Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography

Background: Sudden visual loss is a common complaint among patients of different ages with variable presentations. Some patients describe it as a gray-black curtain that gradually descends, blurring, fogging, or dimming vision. It usually lasts a few minutes but can persist for hours. The frequency varies from a single episode to many during a day; it may continue for years but more often lasts for seconds to hours. Ischemia is the most common mechanism of acute visual dysfunction and it can affect any aspect of the visual system.

Pathophysiology: Ischemia reduces delivery of oxygen and other important nutrients to tissues, causing metabolic compromise of cells. Functional deficit may be temporary or permanent, depending on the degree of damage. Nomenclature of eye ischemia as given by Hedges and others includes the following:

• Transient visual obscuration (TVO) - Episodes lasting seconds that are associated with papilledema or increased intracranial pressure

• Amaurosis fugax - Brief, fleeting attack of monocular partial or total blindness that lasts seconds to minutes

• Transient monocular visual loss (TMVL) or transient monocular blindness (TMB) - A more persistent vision loss that lasts minutes or longer

• Transient bilateral visual loss (TBVL) - Episodes affecting one or both eyes or both cerebral hemispheres and causing visual loss

• Ocular infarction - Persistent ischemic damage to the eye, resulting in permanent vision loss

Mortality/Morbidity:

• TMVL in a person younger than 45 years may be benign; many attacks are probably vasospastic.

• TBVL almost always is associated with severe occlusive disease of the internal carotid artery (ICA) or aortic arch, or bilateral occipital lobe ischemia.

• Patients with ICA disease often have other systemic evidence of atherosclerosis such as coronary and peripheral vascular disease. Smoking, hypercholesterolemia, and hypertension are also risk factors.

Race:

• Whites, especially men, have a high incidence of ICA-origin atherosclerosis.

• Blacks, Chinese, and Japanese have a higher incidence of intracranial occlusive disease.

Sex: A strong male predominance (2:1) exists among patients with severe ICA disease.

	CLINICAL	Section 3 of 10
Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Bibliography

History: For any patient with sudden visual loss, the following information should be obtained:

• Age

• Duration of visual loss or changes

• Whether one eye or both eyes affected

• History of trauma

• Prior episodes/ophthalmologic history

• Symptoms

• Photophobia

• Headache

• Pain

• Comorbid conditions such as hypertension, hypercholesterolemia, collagen vascular disease, hematological disorders, cancer, or drug usage should be asked about.

• A patient with a detached retina presents with the sensation of painless vision loss in one eye, described in the classic presentation as a wall slowly developing over the visual field. The patient also may complain of flashing lights or “spider webs” in the peripheral field.

Physical: Inspect the extraocular area, visual acuity, light or movement perception, visual fields, extraocular movements, and pupil reactivity (including the presence or absence of a relative afferent pupillary defect).

• Initial examination of the external appearance of the eye is part of a good systematic approach. The appearance of the eye is key. A non-injected eye may be painful owing to optic neuritis, cluster headaches, sinusitis, or dental pain. Normal findings on this examination eliminate extraocular causes of visual loss.

• Red and painful eyes should be examined with a slit lamp, both with and without fluorescein staining. Corneal and conjunctival findings such as inflammation, edema, or defect are associated with etiologies such as abrasions, keratopathy, ulcers, and infection, which should become apparent with this examination.

• Intraocular pressure should be measured in patients who have red, painful eyes with normal findings on corneal staining. Elevated pressure points to a diagnosis of acute glaucoma.

• Anterior chamber should be evaluated for hyphema, cells, and floaters. In injected, painful eyes with normal fluorescein examination and pressure, the presence of inflammatory cells in the anterior chamber suggests iritis or endophthalmitis, especially with any recent history or ocular surgery.

• Careful fundus examination is part of a complete ophthalmic assessment. On funduscopy, a detached retina appears gray and detached.

• To differentiate physiologic from hysterical visual loss, the examiner can double the distance between the patient and the tangent screen (ie, visual screen test). In physiologic visual loss, this results in doubling of the size of the central visual field, whereas in hysterical visual loss, the visual field remains the same.

• An optokinetic drum can help identify blindness of hysterical origin. If nystagmus occurs, the patient is seeing the stripes. Moving a mirror (placed close to the patient's face) will cause the eyes to move if vision is present.

• The examination also should include complete cardiac and neurologic evaluation, including murmurs and carotid bruits.

Causes: Multiple conditions are associated with transient visual loss. They can be classified according to origin or pathogenesis, but for the purpose of this article they will be outlined by source.

• Wray has classified TMVL into 3 different groups based mostly on pathogenesis; they include the following:

• Type 1 is characterized by loss of all or a portion of vision in one eye, lasting seconds to minutes, with full recovery. It is usually secondary to an embolic phenomenon. The attacks have been related to an ICA origin associated with ulceration but not critical narrowing.

• Type 2 includes visual loss due to hemodynamically significant, occlusive, low-flow lesions in the ICAs or ophthalmic arteries. Symptoms are more frequent, less rapid in onset, and longer in duration than type 1 attacks, with gradual vision recovery.

• Type 3 is thought to be due to vasoconstriction or vasospasm.

• Cardiovascular: The pathophysiology can be explained by atherosclerotic cerebrovascular disease. The visual disturbances usually appear as dark or gray; a descending shade may appear. Visual loss lasts for minutes (10-15 minutes) and painlessly returns to normal afterwards.

• Embolic: Retinal arteriolar emboli are the most important and common ophthalmoscopic abnormality arising from the carotid artery, aorta, cardiac valves, or heart itself. Particles consist mostly of platelets or fibrin, calcified emboli, or cholesterol crystals.
  • Cholesterol crystals are observed most frequently. These are called Hollenhorst plaques and are found at the bifurcation of the retinal arterioles. They arise from atherosclerotic plaques in the ICA in the carotid siphon or the aorta, and are usually bright, refractile, and small (10-20 micrometer in diameter), often not impeding flow.

  • They disappear rapidly but damage the vessel wall, producing a sheathing reaction. They are difficult to see, but placing pressure on the eye may cause the crystals to move and become visible through the ophthalmoscope. The platelet-containing types are gray in color and commonly extend to the small retinal arteries. The calcified crystals arise most commonly from calcified heart valves. They are white and usually remain in one position, blocking blood flow.

• Stenotic vascular disease: This includes carotid or vertebral artery atherosclerotic disease, fibromuscular dysplasia, arteritis, and dissection.

• Cardiac disease: Cardiac causes include atrial myxomas, endocarditis, or dyskinetic wall segment. They predispose patients to the formation of platelet-containing emboli. Dissection usually involves the pharyngeal ICA and can be precipitated by trauma or can begin spontaneously. Pain in the neck, jaw, face, or head, ipsilateral Horner syndrome, ipsilateral spells of TMVL, and transient hemispheric attacks (THA) are frequent features.

• Hematological: Symptoms and signs are caused by formation of clots or platelet-containing emboli and include hypercoagulable states, antiphospholipid syndrome, and anemia.

• Local orbital or ocular disease

• Angle-closure glaucoma: In open-angle glaucoma, the aqueous humor has access to the trabecular meshwork. In angle-closure glaucoma, this access is blocked by the peripheral iris.
  • The iris may close the angle in one of 3 ways: (1) pupillary block—the iris is bowed forward by aqueous humor, which is unable to get through the pupil because it is adherent to the lens (posterior synechiae); (2) obstruction of the trabecular meshwork directly without pupillary block as a result of posterior pressure from the ciliary body, vitreous, or lens or because of anterior rotation and swelling of the ciliary body; and (3) peripheral anterior synechiae, which are adhesions formed between the peripheral iris and the angle structures.

  • The diagnosis is not difficult when the presentation is typical—a painful, red eye with increased intraocular pressure that is accompanied by diaphoresis, nausea, and vomiting. Atypical presentations include chronic angle closure or an acute closure without pain. The presence of a midposition, fixed pupil in an eye with reduced vision can suggest unrecognized angle-closure glaucoma. All presentations can be confirmed by tonometry or gonioscopy. Treatment consists of topical miotics and beta-blockers, systemic carbonic anhydrase inhibitors, hyperosmotic agents, and perhaps analgesics and antiemetics. Ophthalmologic consult is warranted; when pupillary block is suspected, iridectomy remains the primary surgical management.

• Papilledema/neoplasm: Intracranial hypertension causes persisting visual loss by mechanically compressing or physiologically destroying the optic nerve. The visual consequences of postpapilledema optic atrophy start with peripheral visual field constriction, typically most prominent in the inferior nasal or upper nasal quadrant, followed by loss of central visual field with decline in central acuity and dyschromatopsia. A relative afferent pupillary defect can be found in most instances in which visual field or acuity loss is asymmetric between eyes. Visual field defects can include central/paracentral and arcuate scotomas, or nasal steps. Ophthalmoscopy will show a swollen, pale, or normal retina.

• Intraocular foreign bodies: These are small particles that have penetrated the cornea or sclera. This commonly occurs in the workplace; the signs can be subtle, causing only light erythema and local discomfort. Visual acuity often is decreased markedly, but normal visual acuity is possible and does not rule out an intraocular foreign body. Smaller objects may produce few, if any, signs or symptoms and may be difficult to discover without a high index of suspicion. With large objects, disruption of the anterior segment, a visible penetration site, hyphema, or cataract may be obvious.

• Ocular ischemic syndromes: Persistent eye ischemia can be classified into central retinal artery occlusion (CRAO), branch retinal artery occlusion (BRAO), or ischemia of the optic nerve, which is caused by involvement of the posterior choroidal blood supply of the nerve (anterior ischemic optic neuropathy or AION).
  • Origin of CRA from the ophthalmic artery is variable. The vessel has intraorbital, intravaginal, and intraneural segments on its way to the retina. To reach the fundus, the CRA penetrates the lamina cribrosa. At this point, it narrows; the tissue around the vessel is a mechanical barrier to dilatation. This area is not visible by ophthalmoscope and is most often the site of embolic or inflammatory diseases (eg, giant cell arteritis).

  • The major symptom of CRAO is sudden, painless blindness with persistent visual loss. Perception of hand movement or light can be preserved in parts of the visual field. Diagnosis is confirmed by ophthalmoscopy, which reveals partial or complete arrest of retinal circulation. Cardinal signs include attenuated retinal arteries and veins (very early only), a cloudy whitening of the retina (ie, edema) with the consequent cherry-red spot in the macula in a patient who has lost vision in one eye. Shortly after occlusion, segmentation of the blood column with slow streaming of veins is seen without recovery of vision. If the occlusion lasts more than 1 hour, the retina becomes irreversibly infarcted.

  • In BRAO, visual defect and retinal ischemia are more focal and have an altitudinal, lateral, or scotomatous quality. The incidence of carotid artery and valvular disease is not very different than in CRAO, but temporal arteritis is less often the cause.

  • In AION, the patient usually develops painless visual loss in the eye, which is noted on awakening in the morning and not worsening thereafter. The degree of loss is variable but most often not complete. Ophthalmoscopy shows edema of the optic disc and splinter hemorrhages at the disc margins. When the ischemia is posterior to the disc, the disc may look normal, but this is quite uncommon and may point toward arteritis as the cause. Subsequent involvement of the other eye is common.

  • Retinal vein occlusions are retinal vascular disorders that are classified clinically as branch (BRVO), hemispheric, or central vein occlusions (CRVO). BRVO involves one of the branch retinal veins. Most involve the superior or inferior temporal arcades and occur at an arteriovenous crossing where the vein is compressed by a sclerotic artery. The superior or inferior temporal arcades cause macular vein occlusion with profound visual deficit. Hemispheric vein occlusion involves the venous drainage of either the superior or inferior retina.

  • BRVO affects males and females equally, occurring most frequently in adults aged 60-70 years. Regardless of the primary pathogenic processes, that disease of the arterial wall and the presence of common adventitia between artery and vein at arteriovenous crossings play a role in the pathogenesis is clear. The common symptoms of BRVO are blurring and distortion of vision. During the acute stage, multiple superficial and deep retinal hemorrhages are seen in a pie configuration in the distribution of the affected vein. The veins in the occluded segment usually are dilated and tortuous.

  • Fluorescein angiography is helpful to delineate the hemodynamic changes that occur in the retinal vasculature. Angiography usually shows that the vein is not occluded completely, but the venous return is slow. Approximately 50% of patients recover good visual acuity, although 2 complications may lead to reduced visual acuity—macular edema, which develops in more than 50% of patients, and retinal neovascularization. Management of both involves photocoagulation to ablate the ischemic peripheral retina.

  • CRVO involves occlusion of the main central vein, which usually occurs at the level of the lamina cribrosa. This occlusion interferes with the drainage of the whole retina. The mechanism is unknown, but the most important local factor is chronic open-angle glaucoma, which is present in over 20% of patients. CRVO is primarily a disease of the elderly but well-documented cases in younger persons have been reported.

  • CRVO is of 2 types—nonischemic or ischemic; nonischemic is the more common form. Visual complaints vary from mild or moderate blurring of vision, which may be transient. Visual fields are usually normal except for occasional central scotomas. Ophthalmoscopic features include moderate dilatation and tortuosity of all retinal veins with multiple punctate hemorrhages in the peripheral retina and few scattered retinal hemorrhages in the posterior pole. Most hemorrhagic activity resolves over several months. Some patients may be left with some permanent visual loss from the nonresolving cystoid macular edema, macular cystic degeneration, macular retinal pigment epithelial changes, and preretinal fibrosis.

  • Ischemic CRVO occurs in older individuals who have a higher incidence of systemic vascular disease, preexisting glaucoma, and ocular hypertension. These patients have sudden, painless vision loss. Vision usually is decreased markedly, but the majority of patients will be able to count fingers or see hand movement. Peripheral visual fields are almost always normal with a dense central or centrocecal scotoma.

  • The ophthalmoscopic features include marked tortuosity and dilatation of all the retinal branch veins, diffuse retinal hemorrhages extending from the optic disc to the periphery of the fundus, and multiple cotton-wool patches. The prognosis is poor; central vision seldom recovers owing to ischemic maculopathy or cystic macular degeneration, macular holes and cysts, and macular epithelial fibrosis. No effective treatment is known, but photocoagulation (panretinal) causes regression of iris neovascularization and even prevents its development.

• Ruptured globe: This results from full-thickness traumatic disruption of the sclera or cornea as a result of blunt or penetrating trauma to the eye.
  • Open globe should be suspected in any patient who has a history of trauma to the eye, especially with a laceration or puncture wound that extends through the eyelid, followed by pain and decreased visual acuity.

  • On examination, visual acuity often is decreased. Flattening of the anterior chamber or hyphema may be present. Note alteration of the pupil size, shape, or location and conjunctival edema or hemorrhage. Extrusion of ocular contents may be seen, and the eye may have a deflated appearance. Leakage of aqueous humor from the anterior chamber may become apparent during examination with fluorescein staining (ie, Seidel test). Intraocular pressure frequently is decreased, although it should not be measured if an open globe is suspected.

• Miscellaneous

• Hysteria/malingering
  • The patient with hysterical blindness or loss of vision will, despite alleged loss of vision, still be capable of maneuvering in a room. The pupillary reactions are normal. The loss of vision is a subconscious conversion symptom. A purely functional loss of vision can be assumed when the visual field is markedly constricted, orientation when walking is intact, and pupillary reactions to light are normal.

  • The transition between a hysterical or malingering patient and one with an aggravated loss of vision is fluid. If the patient indicates a unilateral loss of vision, the examination should be conducted in such way that the patient does not know which eye is being tested or the actual size of the optotypes, and a relative afferent pupillary defect should be present.