Ординатура / Офтальмология / Английские материалы / Neuro-Ophthalmology_Kidd, Newman, Biousse_2008
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Figure 2–7 Acute idiopathic blind spot enlargement syndrome (AIBSE). A, The right optic nerve head appearance in a patient with chronic AIBSE. Note the concentric deep pigmentary changes around the optic nerve head with preservation of the normal optic nerve color. B, Visual field of the right eye shows enlargement of the physiologic blind spot.
is often abnormal, especially the multifocal ERG. AIBSE generally resolves over several weeks or months but occasionally will recur in the same or opposite eye. AIBSE may be one manifestation of a group of disorders designated as acute zonal occult outer retinopathy (AZOOR) and including AIBSE, the multiple evanescent white-dot syndrome (MEWDS), acute macular neuroretinopathy (AMN), and the pseudo-presumed ocular histoplasmosis syndrome (P-POHS). The group is linked because of a common involvement of the outer retinal layers, possibly by an autoimmune or viral etiology, especially in young women. Funduscopic changes may be minimal but the ERG is usually abnormal.
RETINOVASCULAR OCCLUSION AND RETINAL DETACHMENT
The fibers that form the optic nerve originate in the ganglion cells, one of the most inner layers of the retina.1,2 The axons of the ganglion cells lie superficial to the ganglion cell layer and are designated as the nerve fiber layer before their coalescence into the optic nerve. Damage to the ganglion cell body or the nerve fiber layer is tantamount to damage to the optic nerve; there will be visual loss, a relative afferent pupillary defect if unilateral, and ultimately optic nerve atrophy. Because the central retinal arterial and venous circulations subserve the inner layers of the retina (including the ganglion cell and nerve fiber layers), retinal vascular occlusive events will result in inner retinal damage, visual loss, and a relative afferent pupillary defect.
Acute vascular events involving the inner retina have a dramatic and distinct funduscopic appearance, allowing for immediate correct diagnosis. When a retinal artery becomes occluded the normally transparent retina supplied by that artery becomes white and edematous. There may be segmentation of the arteriolar blood column (boxcarring) and a reduction of the arteriolar lumen. A visible embolus
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is present in 10% to 20% of patients with a central retinal artery occlusion and 60% to 70% of patients with a branch retinal artery occlusion.
Occlusion of the central retinal artery (CRAO) (Fig. 2–8) is a medical emergency. Central and severe visual loss typically occurs painlessly and without warning. Occasionally, patients may experience episodes of transient monocular blindness before complete visual loss, especially in those cases related to ipsilateral carotid disease or giant cell arteritis. The classic funduscopic appearance of CRAO is central retinal whitening surrounding a cherry red spot in the macular region. This occurs because the retina is very thin at the level of the macula and the underlying choroidal circulation shows distinctly red against the white, swollen, ischemic surrounding retina. In the acute phase, the optic nerve head appears normal because its blood supply is not the central retinal artery but rather branches from the ciliary circulation. In time, however, with death of the inner retinal layers, including the ganglion cell layer and the nerve fiber layer, the optic nerve becomes pale. The retinal vessels ultimately become narrowed and sheathed. Most cases of CRAO are caused by an embolus obstructing either the central retinal artery or the ophthalmic artery. The standard of care if the patient is seen within a few hours of acute onset is to initiate a host of measures designed to improve circulation to the retina, including ocular massage to dislodge the embolus, breathing a mixture of 95% oxygen and 5% carbon dioxide to promote vasodilation, systemic administration of acetazolamide to reduce intraocular pressure, and anterior chamber paracentesis to dramatically reduce intraocular pressure. Unfortunately, only rarely is vision restored. The administration of selective arterial thrombolytics for this entity is controversial.
In an ophthalmic artery occlusion, both the central retinal artery circulation and the ciliary circulation are compromised, resulting in ischemia to the inner and outer retina and the optic nerve. The funduscopic appearance is that of both retinal and optic nerve swelling, with no cherry red spot (the choroidal circulation is also compromised). In branch retinal artery occlusions (Fig. 2–9), the area of retinal whitening and edema, as well as the vision and visual field loss, is determined by the location and amount of retina subserved by that particular vessel.
Figure 2–8 Central retinal artery occlusion in the right eye. Note the overall whitening of the retina and the preservation of a cherry red spot at the fovea.
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Figure 2–9 Superior branch retinal artery occlusion in the left eye. Note the small embolus at the origin of the involved branch artery at the top of the optic nerve head and the whitening of the involved superior inner retina.
Occlusion of the central retinal vein (CRVO) (Fig. 2–10) produces a dramatic funduscopic appearance, although visual loss may be minimal. The veins are markedly dilated with diffuse hemorrhage involving the superficial and deep layers of the retina. There are usually cotton wool spots (small infarctions of the nerve fiber layer) and swelling of the optic nerve head. Descriptions of CRVO include “blood and thunder” and “pizza pie.” Underlying hypertension and hypercoagulability need to be considered in these patients.
A retinal detachment (Fig. 2–11) occurs when the connections between the overlying retina and the underlying retinal pigment epithelium (and the nourishing choroidal blood supply) are severed. If the detachment involves the retina centrally, this results in poor central vision and a relative afferent pupillary defect. Ophthalmoscopy will reveal the detached retina ballooning forward or simply a red reflex with an obscured view of the fundus. Myopic patients are especially vulnerable to retinal detachments, as are patients who have recently had intraocular surgery or ocular trauma, or who have a family history of retinal detachment.
Figure 2–10 Central retinal vein occlusion with optic nerve head swelling, diffuse hemorrhages, and cotton wool spots.
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Figure 2–11 Superior retinal detachment of the left eye.
Detachments are often heralded by photopsias (flashes of light). If the detachment originates peripherally, there may first be a period of time when the patient notices a veil or shadow over a portion of the visual field before central visual involvement. Prompt evaluation by an ophthalmologist may preempt further detachment and allow for the appropriate reattachment surgery.
RETINAL DEGENERATIONS
When optic neuropathies are bilateral and symmetric, all criteria for diagnosis of optic neuropathy may be met except for the presence of a relative afferent pupillary defect. These primary bilateral optic neuropathies may be difficult to distinguish from a group of retinal disorders, commonly designated retinal degenerations and dystrophies, in which secondary optic disc pallor occurs bilaterally.4,5 Retinal disorders that may “masquerade” as bilateral optic neuropathies include vitamin A deficiency retinopathies, toxic retinopathies, and carcinoma-associated and melanoma-associated paraneoplastic retinopathies.4 Clues to their diagnosis include photopsias (often considered the “agonal cry” of the dying photoreceptor), subtle retinal pigmentary changes, and retinal arterial attenuation or narrowing. Electrophysiologic testing, especially the ERG and multifocal ERG, are usually diagnostic.
The cone dystrophies (Fig. 2–12) are characterized by bilateral loss of central vision, profound color vision deficits, and often a relatively normal-appearing fundus examination except for bilateral temporal disc pallor. The cone dystrophies are commonly sporadic, although inherited forms have been reported. Visual acuities typically deteriorate to the 20/200 to 20/400 level. Clues to suggest retinal cone dysfunction include the profound dyschromatopsia; photophobia; an inability to see as well in bright as in dim light (hemeralopia), retinal arterial attenuation; and, eventually, changes in the appearance of the macula, often resembling a bull’s-eye (Fig. 2–13). The ERG will show abnormalities of photopic function and is diagnostic.
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Figure 2–12 Cone dystrophy masquerading as bilateral optic neuropathy. A, Funduscopic appearance with pale optic nerves bilaterally, but note the definite attenuation of the arteries and the subtle macular changes. B, Goldmann visual field in this patient showing relative central scotomas consistent with cone dysfunction but mimicking optic neuropathies.
Figure 2–13 Bull’s-eye maculopathy in a patient with cone dystrophy.
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Some causes of toxic retinopathy that may masquerade as bilateral optic neuropathies include vigabatrin, chloroquine and hydroxychloroquine, deferoxamine, digoxin, quinine, and thioridazine. Vitamin A deficiency retinopathy occurs in the setting of protein-calorie malnutrition in developing countries, but in the developed world it is more likely to be encountered in patients with malabsorption from liver or gastrointestinal disease, including those patients who have had bariatric gastric bypass surgery.
Two types of paraneoplastic retinopathy and multiple different antigens have been well-described. In carcinoma-associated retinopathy (CAR), there is a selective loss of photoreceptors, photopsias, hazy vision, and nyctalopia but often a normal funduscopic appearance except for retinal arterial attenuation. In melanoma-associated retinopathy, there is selective damage to the bipolar cells, prominent photopsias and nyctalopia, and also typically normal-appearing fundi, especially early in the course of visual loss. Paraneoplastic retinopathy classically has a much faster rate of progression than any of the inherited retinal dystrophies, but it may be the first manifestation of the malignancy. The ERG is diagnostic in these disorders.
Investigations
Because distinction of an optic neuropathy, especially a bilateral optic neuropathy, from a retinopathy can sometimes be difficult on the basis of clinical manifestations and retinal appearance alone, ancillary testing is commonly required.4 Fluorescein angiography can sometimes help in diagnosis, especially in regard to retinal vascular disease, central serous retinopathy, and some of the other maculopathies. Ocular coherence tomography (OCT) uses a laser slit beam projected onto the retina to obtain a cross-sectional image and is also particularly helpful in identifying subtle maculopathies.
However, when the distinction between retinal disease and optic neuropathy is not obvious, the gold standard for evaluation is electrophysiology, in particular the full-field ERG and the multifocal ERG.4 The full-field ERG is the mass-electrical response of the retina to flash stimulation, using varied colored lights presented at different frequencies and in different illuminations. The standard ERG includes a scotopic rod response to a dim blue or white stimulus, a maximal response to bright white light in the dark-adapted eye (mixed rod and cone response), a photopic (cone) response, and a 30-Hz flicker (cone) response. The different wave forms reflect the responses from different parts of the retina, but the ganglion cell layer and the nerve fiber layer are not represented, allowing for differentiation of abnormalities of deeper layers of the retina. Unfortunately, however, disease limited to the macula does not cause full-field ERG changes (the contribution from the macula is overcome by the total retinal response). The multifocal ERG is a more recent technique in which focal ERGs from multiple locations are simultaneous recorded and mathematically extracted, generating a retinal response topography map. One can correlate focal retinal dysfunction with visual field abnormalities and funduscopic appearance, particularly allowing for the detection of subtle macular abnormalities.
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It is an Optic Neuropathy!
Once one has determined by history and examination that a patient does indeed have an optic neuropathy, then a differential diagnosis as to the underlying cause of that optic neuropathy must follow.6 Essentially all categories of disease processes must be considered (Table 2–1). Unfortunately, the optic nerve has a very limited repertoire of how it can express itself when it is damaged or perturbed (Fig. 2–1). If the pathology involves the optic nerve head, one may see swelling of the nerve, so-called disc edema. If the locus of the pathology is behind the eyeball, termed retrobulbar, then it is likely that the optic nerve will appear normal at the time of acute visual loss. Ultimately, after 4 to 6 weeks, pallor will ensue if permanent damage has occurred. Important clues in establishing the etiology of an optic neuropathy include the age of the patient, the tempo of onset and progression of visual loss, the presence or absence of pain, the presence or absence of bilateral involvement, the level of visual acuity, the pattern of visual field loss, the appearance of the optic nerve head, and the presence or absence of associated signs.
Acknowledgments
This work was supported in part by a departmental grant (Department of Ophthalmology) from Research to Prevent Blindness, Inc, New York, NY, and by core grant P30-EY06360 (Department of Ophthalmology) from the National Institutes of Health, Bethesda, Maryland. Dr. Newman is a recipient of a Research to Prevent Blindness Lew R. Wasserman Merit Award.
TABLE 2–1 Categories of Disease Processes That Can Cause an Optic Neuropathy
Inflammatory
Infectious
Noninfectious
Vascular
Compressive/Infiltrative
Neoplastic
Non-neoplastic
Hereditary
Toxic/metabolic
Traumatic
Mechanical
Elevated intracranial pressure
Elevated intraocular pressure
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REFERENCES
1.Rizzo JF III: Embryology, anatomy and physiology of the afferent visual pathway. In Miller NR, Newman NJ, Biousse V, Kerrison JB (eds): Walsh and Hoyt’s Clinical Neuro-Ophthalmology, 6th ed, vol 1. Baltimore, Lippincott Williams & Wilkins, 2005, pp 3–82.
2.Albert DM, Jakobiec FA: Principles and Practice of Ophthalmology, 2nd ed. Philadelphia, WB Saunders, 2000.
3.Spalton D, Hitchings R, Hunter PA: Atlas of Clinical Ophthalmology, 2nd ed. Philadelphia, JB Lippincott, 1992.
4.Sandbach JM, Newman NJ: Retinal masqueraders of optic nerve disease. Ophthalmol Clin North Am 2001;14:41–59.
5.Newman NJ: Optic disc pallor: A false localizing sign. Surv Ophthalmol 1993;37:273–282.
6.Van Stavern GP, Newman NJ: Optic neuropathies. An overview. Ophthalmol Clin North Am 2001;14:61–71.
3Orbital Disease
GEOFFREY E. ROSE DAVID H. VERITY
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The Assessment of Orbital |
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Ancillary Tests for Orbital |
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Disease |
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Disease |
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Clinical History in Orbital |
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Common Orbital Diseases |
Disease |
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Benign Orbital Diseases |
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Clinical Examination for Orbital |
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Malignant Orbital Diseases |
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Disease |
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Key Points
An accurate clinical history and patient assessment are essential in the management of orbital disease.
Orbital examination includes a full assessment of the following: optic nerve function (visual acuity, color vision, visual fields, pupil reactions, and disc assessment), axial and nonaxial globe position, ocular balance and motility, and intraocular and periorbital structures. Systemic examination is guided by the symptoms.
The imaging of choice for orbital disease is CT. MRI may provide further detail of intrinsic optic nerve disease and orbital apical or intracranial pathology.
Ultrasonography has higher resolution than CT and MRI and is valuable in assessing intraocular lesions and anterior orbital masses—in particular vascular lesions.
Orbital inflammation is a not a diagnosis but a tissue response to a wide range of pathologies, and immunosuppression should not be instituted until an adequate biopsy has been obtained. The exceptions to this general principle are typical scleritis, myositis, thyroid eye disease, and characteristic orbital apex syndrome, in which delay in suppression of apical inflammation may jeopardize visual outcome.
Similarly, the term “orbital pseudotumor” is not a diagnosis, has often led to inappropriate management, and is no longer in use.
Thyroid eye disease is the most common cause of unilateral and bilateral proptosis. Management of aggressive disease consists of immunosuppression in the early, “active” phase, with nonresponsive patients requiring urgent decompression in the presence of optic neuropathy. Stable, inactive disease is managed by orbital decompression for exophthalmos, followed by correction of muscle imbalance and lid malposition.
Subacute lacrimal gland inflammation, unresponsive to a few weeks of nonsteroidal treatment, may be due to underlying carcinoma and a specialist opinion should be sought without delay.
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Although the orbit is affected by a broad spectrum of pathology—including structural, inflammatory, infectious, vascular, neoplastic and degenerative processes— the symptoms and signs of orbital disease are limited (Table 3–1). To the astute clinician, however, a thorough history and examination for both ocular and systemic disease usually leads to a concise differential diagnosis and can guide further investigation. The clinical assessment of orbital disease, radiologic interpretation, and an approach to diagnosis, investigation, and management of commoner benign and malignant orbital diseases are presented in this chapter.
The Assessment of Orbital Disease
Clinical history provides a good guide to likely orbital pathology, particularly taking into consideration the patient’s age, the presence and nature of pain, and the speed of onset of symptoms. Imaging, of which computed tomography (CT) remains the most useful primary modality for orbital conditions, tends to provide confirmatory evidence for the likely diagnosis and also helps define the extent of disease.
CLINICAL HISTORY IN ORBITAL DISEASE
Pain
The nature, intensity, location, and duration of orbital pain should be assessed: sharp, lancinating pains—often localized to “under the upper eyelid” and with bursts of profuse watering—come from ocular surface drying, typically resulting from incomplete lid closure because of proptosis; a history of sleeping with open eyelids (“nocturnal lagophthalmos”) should be sought. Inflammation from deep within the orbit, or raised intraorbital pressure, is often associated with relentless ache and may be due to malignancy, arteritic or sclerosing inflammations (such as Wegener’s granulomatosis), or thyroid orbitopathy. Factors influencing the pain should be elicited: distension of orbital varices give rise to a deep-seated ache after straining or bending forward, whereas the chronic pain of orbital myositis is markedly exacerbated by eye movements that relax (stretch) the affected muscle.
Position of the Globe
Proptosis may be first noted by a friend or relative of the patient, and old photographs—preferably in which the patient is not smiling—may help establish the duration of ocular displacement. Progression in the degree of proptosis is relevant: the long globe of unilateral high myopia (refraction and ultrasound are confirmatory) may result in stable pseudoproptosis (Fig. 3–1); likewise, the patient with shallow orbits may have apparent, but unchanging, constitutional exophthalmos. Exophthalmos that increases on Valsalva maneuver—either deliberate or unintentional (as on bending)—is typically associated with distensible venous anomalies (Fig. 3–2). Pulsatile proptosis is due to transmission of either vascular pulsation or changes in cerebrospinal fluid (CSF) pressure, the latter occurs with sphenoid wing hypoplasia (neurofibromatosis), after surgical