Ординатура / Офтальмология / Английские материалы / Clinical Ocular Pharmacology 5th edition_Bartlett, Jaanus_2008

produce mydriasis and the Horner’s pupil dilates larger than the normal pupil. In a study of patients with Horner’s syndrome, it was found that 71% of the patients were sensitive to 1% phenylephrine. A 1% phenylephrine dilution is obtained by mixing one drop of 10% commercially available phenylephrine with nine drops of irrigating solution or normal saline.

Application of Pharmacologic Test Results.

Table 22-4 summarizes the expected responses of the Horner’s pupil to cocaine and hydroxyamphetamine. This current schema for drug testing in Horner’s syndrome applies only to complete lesions of the oculosympathetic pathway and should not be relied on in patients with incomplete lesions. Cocaine is used initially to confirm the presence of Horner’s syndrome, whereas hydroxyamphetamine is used several days later to localize the lesion to the central, preganglionic, or postganglionic sympathetic pathway. Note that presently no pupillary drug test clearly distinguishes central from preganglionic lesions.

Management

It is crucial to differentiate central or preganglionic lesions from postganglionic lesions, because appropriate patient management depends on accurate localization of the lesion. When the detailed history, clinical examination, and pharmacologic testing indicate a central or preganglionic lesion of unknown etiology, the patient should be referred to a thoracic surgeon or internist because of the risk of malignancy. Because of the risk of neuroblastoma, pediatric patients with early onset Horner’s syndrome should also be investigated. Neurologic consultation should be considered when central lesions are suspected.

Postganglionic lesions are most likely associated with a benign vascular headache syndrome. Such patients with unilateral headache and isolated postganglionic Horner’s syndrome usually follow a benign course and need no further evaluation. However, if the headaches do not spontaneously resolve within several months or if objective involvement of the trigeminal nerve or other parasellar cranial nerves is documented, then further neurologic investigation should be considered. Figure 22-5 summarizes the management of the patient with Horner’s syndrome of unknown etiology.

ADIE’S SYNDROME

An association between tonic pupils and hyporeflexia is known as Adie’s syndrome. A tonic pupil alone without associated hyporeflexia is termed Adie’s pupil.

Etiology

The etiology of Adie’s pupil is usually unknown. It is generally accepted, however, that the lesion is in the ciliary ganglion,with damage to the postganglionic neurons serving the ciliary muscle and iris sphincter. Adie’s pupil frequently follows a mild upper respiratory infection, and thus in some cases it may be associated with a nonspecific viral illness. In other instances orbital trauma can produce the syndrome. Surgical repair of orbital floor fractures can also cause Adie’s pupil due to damage to the ciliary ganglion or postganglionic neurons. Adie’s-like pupils with accommodative paresis have occurred as complications after peripheral retinal laser treatment. They result from laser damage to cholinergic nerve fibers, beneath the treated area, that innervate the ciliary body and iris sphincter. An Adie’s-like sector palsy, without accommodative insufficiency, can follow argon laser trabeculoplasty for treatment of certain glaucomas. When Adie’s pupil occurs bilaterally, it may be associated with orthostatic hypotension, Riley-Day syndrome, or neurosyphilis.

The most widely accepted interpretation of Adie’s pupil involves the concept of aberrant regeneration of nerve fibers. The parasympathetic accommodative fibers in the ciliary ganglion are believed to be far more numerous than those that supply the iris sphincter. After destructive ciliary ganglion disease, nerve fiber regeneration may occur, with some accommodative fibers becoming misdirected and supplying the iris sphincter. This aberrant regeneration results in attenuation or loss of the pupillary light response, with preservation of constriction of the pupil in accommodation—so-called light-near dissociation. Although this hypothesis does not explain the hyporeflexia that often accompanies the ocular findings in Adie’s syndrome, the syndrome may represent a form of mild polyneuropathy, accounting for the diminished deep tendon reflexes. In rare cases Adie’s syndrome and a severe polyneuropathy can be associated with underlying malignant disease. Perhaps the most noteworthy difference between the clinical signs of Adie’s pupil

Anhidrosis, dilation with 1% hydroxyamphetamine

Central or preganglionic Horner's syndrome

No anhidrosis, no dilation with 1% hydroxyamphetamine

Postganglionic Horner's syndrome

and those of isolated third-nerve pupillary palsy is the presence of light-near dissociation in the former and its absence in the latter.

Diagnosis

Clinical Evaluation. Adie’s pupil is a benign disorder. A diagnosis of Adie’s pupil eliminates the need for elaborate and expensive neuroradiologic investigations. Box 22-4 lists the primary clinical characteristics diagnostic of Adie’s syndrome.

Adie’s pupil is unilateral in 80% to 90% of cases. Approximately 4% become bilateral each year. In the

Box 22-4 Diagnostic Signs in Adie’s Syndrome

Relative mydriasis in bright illumination

Absent or poor light reaction

Slow (tonic) contraction to prolonged near effort Slow redilation after near effort

Vermiform movements of pupillary margin (i.e., sector palsies of iris sphincter)

Accommodative paresis Diminished deep tendon reflexes Onset in third to fifth decadea Women affected in 70% of cases

aCan rarely occur in children.

acute stage, the pupil is usually dilated and reacts very poorly to light. The tonic pupil often changes size in a random manner, possibly being larger in the morning and smaller in the afternoon. Adie’s pupils tend to become smaller over time. Some patients who have been monitored for several years have shown a strikingly progressive miosis of the affected pupil.The gradual constriction is more marked than the normal miosis of aging. The dilated pupil usually returns to its original size within a few months; after approximately 2 years a very slowly progressive additional miosis occurs.

In a patient with an Adie’s pupil that is larger than the normal pupil in darkness, the condition is most likely of very recent onset.The tendency of Adie’s pupils to become progressively miotic and bilateral with age suggests that many Adie’s pupils eventually become disguised as Argyll Robertson–like pupils or simply become inconspicuous among the smaller pupils of the elderly.

The reaction of an Adie’s pupil to an accommodative stimulus is very sluggish and poor. The typical slow and tonic near response serves as the mechanism for the most distinguishing clinical feature of this syndrome—namely, tonic and sluggish redilation as the patient changes fixation from near to distance.

Of patients with Adie’s pupil, 50% to 90% demonstrate significantly impaired or absent deep tendon reflexes, and this sign serves as a helpful clinical confirmation of the diagnosis. Most patients have tendon reflexes that are abnormal throughout the body, but the ankles and triceps

Pharmacologic Evaluation. The denervated iris sphincter in Adie’s pupil shows cholinergic hypersensitivity. This response is expected according to the principle of denervation hypersensitivity. The hypersensitivity does not seem to correlate with either the amount of sphincter denervation, the duration of the Adie’s pupil, or the amount of light-near dissociation. Occasionally, an acute Adie’s pupil shows very little hypersensitivity during the first few weeks after onset but gradually becomes increasingly hypersensitive several months after the initial episode.

Cholinergic hypersensitivity can be tested by using pilocarpine in 0.0625%, 0.1%, 0.125%, or 0.25% solution (Table 22-5).The usefulness of the pilocarpine test in eliciting cholinergic hypersensitivity depends on the presence of a standardized concentration of drug at the iris. Thus any clinical procedure that compromises the corneal epithelium, the use of wetting agents, or other factors that enhance corneal penetration may result in false-positive findings.

A

B

Figure 22-6 Pilocarpine test in a 57-year-old woman with right Adie’s pupil. (A) Before drug instillation. (B) After instillation of 0.125% pilocarpine into each eye, the normal left pupil constricts slightly, whereas the right Adie’s pupil constricts significantly.

360 CHAPTER 22 Neuro-Ophthalmic Disorders

When cholinergic hypersensitivity is being evaluated, it is important that the lowest ambient illumination possible be used to reduce the additional miotic influence of light.This approach enhances judgment of pupil size and response to the dilute pilocarpine. If the patient’s larger pupil becomes the smaller pupil in dim illumination after dilute pilocarpine is instilled into both eyes, the reaction of the larger pupil most likely represents a hypersensitive response and thus indicates a diagnosis of Adie’s pupil. This endpoint does not apply, however, to suspected bilateral tonic pupils, tonic pupils that are smaller than their normal fellow pupils in dim illumination, or long-standing Adie’s pupils that are small in both darkness and normal ambient light.

Management

Because Adie’s syndrome is a benign disorder, the most important aspect in patient management is reassurance. The associated accommodative paresis tends to recover during the first several years, and any visual impairment thus improves. The patient should be advised that the second eye may become involved but that the other changes associated with the syndrome (decreased light reaction and diminished deep tendon reflexes) do not represent significant functional impairments. For many patients the chief concern is the cosmetic appearance of the unequal pupils. Most patients can be reassured that, with time, this should become less noticeable.

Blood tests should be ordered to rule out syphilis in cases of a tonic pupil. If there is associated pain, the patient should receive a workup for an intracranial lesion or orbital mass.

Symptomatic patients may benefit from the instillation of 0.1% to 0.125% pilocarpine into the affected eye three or four times daily. Because of individual variability, various low concentrations of pilocarpine should be attempted to determine the optimum concentration of miotic that alleviates symptoms as periocular discomfort, headache, photophobia, or blurred vision. If a miotic is used in this fashion, the patient should be carefully monitored in anticipation of modifying the drug regimen if the degree of cholinergic hypersensitivity changes over time.

The practitioner can also prescribe tinted lenses,which not only shield the cosmetic appearance of the unequal pupils but also alleviate perception of the Pulfrich phenomenon produced by the anisocoria. Moreover, when affected patients are presbyopic, unequal bifocal powers can be used and frequently serve to alleviate the asthenopia associated with near vision. Reading lenses may be indicated for patients who are prepresbyopic.

UNILATERAL FIXED AND

DILATED PUPIL

A unilateral fixed and dilated pupil in an ambulatory and otherwise healthy patient is seldom associated with a significant neurologic disorder.Yet, historically, the practitioner

has been cautioned to consider this a sign of potentially grave intracranial disease.Although the possible causes of a fixed and dilated pupil are numerous and include potentially destructive vascular and neoplastic processes, the clinician can usually, by comprehensive history and physical examination, narrow the possible diagnoses to

(1) involvement of the intracranial third nerve, (2) Adie’s pupil, or (3) anticholinergic mydriasis.

Because the fixed and dilated pupil is clearly the abnormal pupil, the pharmacologic evaluation involves instillation of a miotic, usually pilocarpine, to assess the degree of impairment of the iris sphincter or its parasympathetic innervation. In most cases only one pupil is dilated and fixed, and instilling the drug into both eyes can avoid false-positive or false-negative drug tests. Constriction of the normal pupil thus indicates that enough pilocarpine was instilled. When both pupils are dilated and fixed, the drops should be placed in only one eye so that any constriction can be attributed solely to the drug.

The following sections consider the most common disorders associated with a unilateral fixed and dilated pupil, including third-nerve palsy, anticholinergic mydriasis, iris sphincter atrophy, and adrenergic mydriasis. Because a dilated pupil does not always characterize Adie’s syndrome, this disorder has been discussed separately.

Third-Nerve Palsy

The patient presenting with the classic signs of a complete third-nerve palsy does not need to undergo pharmacologic testing; the diagnosis can be made on clinical findings alone (Figure 22-7).The most common cause of sudden unilateral third-nerve palsy in an adult with a dilated and fixed pupil and with headache is an aneurysm at the junction of the ipsilateral internal carotid artery and the posterior communicating arteries. The most common cause of sudden unilateral third-nerve palsy in an adult with headache in whom the pupil is spared is diabetes mellitus. The pupillary findings, therefore, are extremely important in the evaluation and management of acute third-nerve palsy.

If, however, the patient exhibits only a unilateral fixed and dilated pupil without evidence of ptosis or extraocular muscle involvement, the clinician should perform the pilocarpine test, first using a 0.125% solution to reveal any cholinergic hypersensitivity as evidence for Adie’s pupil. If there is no local iris damage by slit-lamp examination, no sector palsy of the iris sphincter, and no cholinergic hypersensitivity demonstrated by the 0.125% pilocarpine test, then the condition might be associated with interruption of the preganglionic innervation to the iris sphincter (i.e., third-nerve palsy). If the patient has third-nerve palsy, topically instilled pilocarpine in moderate concentrations activates the muscarinic receptor sites on the iris sphincter. Therefore if 0.125% pilocarpine reveals no cholinergic hypersensitivity, the practitioner

should subsequently instill pilocarpine in a concentration of 0.5% or 1.0%. This should promptly constrict the affected pupil (Figure 22-8). Some patients with intracranial third-nerve palsy may appear to manifest hypersensitivity to low concentrations of pilocarpine. This finding occurs because of the greater mechanical reactivity of the larger pupil; in long-standing cases it also may be caused by actual denervation hypersensitivity of the iris sphincter from transsynaptic degeneration of postganglionic neurons. Thus the clinician should evaluate carefully all clinical signs and symptoms before reaching a final diagnosis.

Anticholinergic Mydriasis

Etiology

Anticholinergic mydriasis, also known as pharmacologic blockade or atropinic mydriasis, refers to a fixed and dilated pupil resulting from the instillation or inoculation into the eye of drugs or substances with anticholinergic properties. Medical personnel such as doctors, nurses,

and pharmacists are particularly susceptible to this condition, because they frequently handle such agents. Commonly, some medication spills over the side of its bottle, and the practitioner or nurse who next handles the bottle comes into contact with the dried medication, which then is easily transferred to the eye by simple rubbing. On occasion, the patient admits to having placed some drops into the affected eye but often cannot recall the name of the medication. In these cases the practitioner should inquire about the color of the medication’s cap, because cycloplegics are commercially packaged with red caps. Patients often have instilled into their mildly irritated eye atropine drops previously prescribed for an episode of anterior uveitis.

Cyclopentolate,homatropine,scopolamine,and atropine are among the most frequently implicated drugs, but many other drugs or substances with anticholinergic properties have also been implicated in anticholinergic mydriasis. Jimson weed (Datura stramonium) grass is found in many parts of the United States, and the entire plant, from root to flower, contains significant concentrations of belladonna

362 CHAPTER 22 Neuro-Ophthalmic Disorders

alkaloids,including atropine,scopolamine,and hyoscyamine. One should suspect jimson weed mydriasis in farmers or in children who have been “picking flowers” if these patients present with an acute-onset unilateral mydriasis. Moreover, the dried pods of the plant often are used in floral arrangements for indoor decoration during the winter. This use may contribute to an increased risk of systemic toxicity in the pediatric age group, because children have been known to consume such “berries.” Fatal cases of systemic toxicity have been reported in children whose stomachs contained the seeds at autopsy. In addition to bilaterally dilated pupils, when the weed is consumed orally the early symptoms of toxicity are those typical of anticholinergic drugs: blurred vision, dryness of the mouth,extreme thirst,constipation,urinary retention, convulsions, dry and flushed skin, diffuse erythematous rash, tachycardia, and fever.

The practitioner should be alert to the possible inoculation into the eye of any drug or substance with anticholinergic properties, including plants, cosmetics, perfumes, or medicines. Unilateral fixed and dilated pupils have been reported after the use of antiperspi-

–

rants, transdermal scopolamine (Transderm Scop) for the prophylaxis of motion sickness, and from direct droplet contamination associated with the use of anticholinergic aerosols for treatment of acute asthma and other airflow obstructions.

Diagnosis

The diagnostic procedure of choice in distinguishing between neurogenic and anticholinergic pupillary paralysis is one or two drops of 0.5% or 1.0% pilocarpine instilled into each eye (Figure 22-9). If the muscarinic

A

B

Figure 22-9 Pilocarpine test in anticholinergic mydriasis.

(A)A 27-year-old man with fixed and dilated left pupil.

(B)After instillation of 1.0% pilocarpine into each eye, the right pupil constricts, whereas the left pupil does not.

receptor sites on the affected iris sphincter have been occupied by an anticholinergic drug,the pilocarpine fails to activate the receptors and constrict the pupil.This simple test quickly and easily differentiates between anticholinergic mydriasis and pupillary paralysis associated with thirdnerve palsy; in the former condition the pupil does not react to the pilocarpine, whereas in the latter it constricts.

Management

Once the diagnosis of anticholinergic mydriasis has been confirmed, the patient should be reassured that with time—usually a few days to a few weeks—the pupil will spontaneously return to its original size and vision (accommodation) will improve as the effects of the substance subside.

Damage to the Iris

Damage to the iris sphincter muscle by high intraocular pressure, trauma, or inflammation may impair pilocarpine’s ability to constrict the pupil. Clinically, these conditions can usually be excluded by a careful history taking and biomicroscopic examination. Mechanical factors associated with malpositioned intraocular lenses or posterior synechiae may also limit movement of the iris. Depending on the extent of iris damage, the pupil may demonstrate complete to nonexistent constriction.

Adrenergic Mydriasis

The pupil that has become dilated in response to topically instilled adrenergic drugs may not be completely immobile. A patient who is unusually sensitive to adrenergic agonists may sustain a dilated pupil as a consequence of the accidental inoculation into the eye of nose drops, nasal sprays, or other substances with adrenergic properties. In addition, some patients with minor corneal epithelial compromise may sustain a dilated pupil after the instillation of decongestant eyedrops. In these instances, however, the adrenergic mydriasis can usually be distinguished from the dilated pupil of third-nerve palsy or anticholinergic mydriasis by the blanched conjunctiva, the residual pupillary light reaction, and the occasional retracted upper eyelid (Figure 22-10). Although dilation associated with adrenergic agonists usually is incomplete and short-lived, the concomitant use of topical epinephrine and timolol for the treatment of glaucoma may occasionally result in the development of longstanding fixed and dilated pupils. A careful history and clinical evaluation of the patient usually eliminate the need for pharmacologic testing. Figure 22-11 summarizes the clinical and pharmacologic evaluations of the patient with anisocoria in which only one pupil is affected.

OPTIC NERVE DISEASE

The diseases that affect the optic nerve can be broadly classified into congenital disc anomalies and acquired

optic neuropathies. This section considers those optic nerve diseases, or optic neuropathies, that are acquired in origin. Optic neuropathies may be due to abnormal accumulation of substances in the nerve or nerve sheath (infiltrative optic neuropathy), invasion of microorganisms (infectious optic neuropathy), localized responses (inflammatory optic neuropathy), demyelinating processes (optic neuritis), toxic reactions, trauma, and nutritional deficiencies.The term optic neuritis has traditionally referred to an inflammatory optic neuropathy of unknown etiology or one associated with multiple sclerosis

(MS), which is a demyelinating disorder. When optic neuritis occurs without disc swelling, the condition is called retrobulbar neuritis. When disc swelling is associated with optic neuritis, the condition is called papillitis. Papilledema is bilateral disc edema associated with increased intracranial pressure (ICP). Optic atrophy, the end stage of many optic neuropathies, is characterized by a pale disc and associated with a relative afferent pupillary defect (RAPD) and possible loss of visual acuity, color vision, and visual field. One example of disc atrophy occurs in cases of Leber’s hereditary optic neuropathy

364 CHAPTER 22 Neuro-Ophthalmic Disorders

(LHON), in which the pallor begins 2 to 4 weeks after vision loss.

Optic Neuropathy Due to

Long-Standing Papilledema

The ophthalmoscopic picture of papilledema, comprising the classic blurred disc margins, nerve fiber layer (NFL) swelling, disc hyperemia, and splinter hemorrhages, is caused by an increase in ICP.This elevated pressure may be due to an increase in cerebrospinal fluid (CSF) level or a space-occupying lesion compressing brain tissue.There are four stages of papilledema, and the clinical appearance of the swollen nerve head varies depending on the stage at which it is being viewed.

The earliest stage, or incipient papilledema, reveals a mild segmental blurring of the NFL bundles. The disc margin is commonly blurred at the upper and lower poles. The disc itself is hyperemic with small splinter hemorrhages in the NFL at the disc margin.

The second stage, acute papilledema, produces increased swelling such that the disc protrudes into the vitreous. The retinal veins often become engorged and tortuous, and NFL infarcts, or cotton-wool spots, may occur close to the disc margin. During the fully developed acute stage, thin retinal folds, known as Paton’s lines, may develop concentric with the disc. Acute papilledema should be considered a medical emergency, whether or not it is fully developed.

If papilledema is present for a prolonged period, then it becomes chronic, the third stage. The disc protrudes forward, and the cup is obliterated. The final stage, chronic atrophic papilledema, is characterized by a flattened grayish white disc with reabsorption of the hemorrhages, exudates, and cotton-wool spots.

Patients with papilledema may have no symptomatology, and visual acuities and fields may remain fairly normal. Most often, however, there is enlargement of the blind spot. Over time, the chronic papilledema may slowly progress toward optic atrophy.Additionally, symptoms related to the underlying pathology may coexist with the papilledema and include headache, nausea, vomiting, and focal neurologic signs if there is a mass lesion.

Etiology

Increased ICP and, thus, papilledema have many causes. Any intracranial space-occupying lesion may create increased ICP. Superior sagittal sinus thrombosis, spinal cord tumors with associated elevated CSF protein, spinal cord injuries, and traumatic brain injury may all cause papilledema.

Diagnosis

The diagnosis of papilledema in its early stages often presents a significant clinical challenge. It involves a combination of stereoscopic observation of the optic disc, visual

field analysis, evaluation of focal neurologic signs, and the patient’s history of transient visual obscurations (5 to 30 seconds of blurring or loss of vision usually associated with postural changes). How quickly papilledema develops depends on the etiology of the increased ICP. Papilledema may develop within 2 to 8 hours if there is an intracranial hemorrhage. The absence of a venous pulsation may be a sign of increased ICP, although as many as 20% of normal patients may not have venous pulsations.

Proper patient management requires a successful differential diagnosis between papilledema and pseudopapilledema (Table 22-6,Figure 22-12). Pseudopapilledema is a congenital anomalous elevation of the optic nerve head that may occur in conjunction with high hyperopia, myelinated nerve fibers, and optic disc drusen. Preinjection fluorescein angiography may show autofluorescence of drusen, but standard fluorescein angiography will not show dye leakage as would be seen in true disc edema. Other useful tests include stereoscopic fundus photography, observation of the peripapillary reflex with a red-free filter, B-scan ultrasonography, and high-resolution orbital computed tomography (CT).

Optic disc edema is the first observable sign of increased ICP.The swelling of the nerve fibers and subsequent transudation of the debris first appear in the inferior

Table 22-6

Distinguishing between Papilledema and

Pseudopapilledema

aspect of the disc, followed by the superior and then the nasal aspects.The temporal part of the disc is last to show swelling. This swelling eventually spreads into the surrounding retina. The disc margins then blur, with obscuration of the small vessels of the disc. As the process progresses, hemorrhage on or near the disc may occur at any retinal level but rarely beyond the radius of the macula. As the papilledema progresses, vision is maintained. Later, visual field defects result that progress to involve fixation and mimic glaucoma as chronic atrophic papilledema sets in.

Other rare complications that may lead to reduced visual acuity are subretinal pigment epithelial neovascularization, choroidal folds, preretinal macular hemorrhage, choroidal and subretinal hemorrhages, macular star formation, and retinal pigment epithelial disease.

In the evaluation of papilledema, magnetic resonance imaging (MRI) or CT is an invaluable and necessary adjunct to determine whether there is a mass in the head or signs of meningeal involvement, which can occur with infection, tumor, or infiltration. MRI is especially sensitive in imaging the enlargement of the subarachnoid space

366 CHAPTER 22 Neuro-Ophthalmic Disorders

around the optic nerves. Magnetic resonance venography should be done if obstruction of cerebral venous drainage is suspected.

Management

If left untreated papilledema can progress to intractable optic atrophy. A diagnosis of true papilledema should always initiate an emergent workup. Medical treatment depends on the cause of the increased ICP, and management should focus on identifying the correct etiology using imaging and lumbar puncture.

Pseudotumor Cerebri

Pseudotumor cerebri (PTC) is a syndrome characterized by papilledema consequent to increased ICP that is not due to a space-occupying intracranial lesion or other cause. PTC, a diagnosis of exclusion, is seen most frequently in young to middle-aged (10to 50-year-old) obese women, with a peak incidence in the third decade.

Etiology

PTC rarely may occur secondary to middle-ear disease, minor head injury, childhood systemic lupus erythematosus (SLE), or toxic conditions such as hypervitaminosis A, tetracycline, amiodarone, and oral contraceptive use.

The condition appears to result from poor resorption of the CSF. Other less likely mechanisms to explain increased ICP include increased blood volume, increased CSF production, and parenchymal brain edema. In more than 50% of cases the underlying etiology is unknown.

Diagnosis

Patients with PTC often present with a generalized headache that is worse in the morning and is exacerbated by Valsalva’s maneuver.Nausea and vomiting may frequently accompany the headache. The patient may also describe transient visual obscurations that last just a few seconds. Although the transient visual obscurations are temporary, a definite potential for permanent blindness exists. This permanent loss of vision is due to optic atrophy or,rarely,to a choroidal neovascular net. Occasionally, diplopia may be reported due to sixth-nerve palsy. Visual field testing is mandatory in all cases of papilledema. In PTC there usually is an enlarged blind spot, arcuate nerve fiber bundle loss, and constricted fields. MRI is effective in establishing the absence of an intracranial lesion and aqueductal stenosis. A lumbar puncture demonstrates a high opening pressure (>200 mm H2O) and a normal CSF profile.

Management

Depending on the visual acuity and visual fields, one determines how quickly intervention is needed. If the patient has no afferent system loss, the first step in the treatment of PTC is to remove any agent that caused it (e.g., tetracycline). If the patient is obese, as is usually the case, then loss of excess weight may reverse

the condition. Some patients have shown a dramatic improvement with as little as a 6% reduction in body mass. Gastric bypass surgery may be indicated in severely obese individuals. If weight loss does not mitigate the PTC, then medical therapy may be tried. Oral carbonic anhydrase inhibitors, such as acetazolamide, may act to reduce the ICP. Acetazolamide may be used as 250 to 1,000 mg in one to four divided daily doses or a 500-mg sustained-release capsule twice daily; larger doses may be necessary in some patients. Acetazolamide may worsen venous sinus thrombosis by exacerbating volume depletion and worsening the clot.

Oral corticosteroids have no role in the chronic treatment of PTC, because there are significant side effects of high-dose oral steroid use,and patients may eventually gain weight. However, in the short term, steroid treatment may be effective in patients with severe or rapid visual deterioration. Corticosteroids must be used with caution because coming off the steroids can cause PTC exacerbation.

If the patient fails to respond to weight loss and medical intervention and if there is a loss of visual function, then surgical maneuvers may be attempted.A shunt between the lumbar spinal cord and the peritoneal cavity (lumboperitoneal shunt) may be tried. As an alternative, fenestration of the optic nerve sheath allows for decompression, which relieves symptoms, reduces papilledema, and improves visual acuity. Mitomycin-C has been shown to increase the success rate of the decompression surgery.

Infiltrative Optic Neuropathy

In infiltrative optic neuropathy, substances that are not normal to the optic nerve or nerve sheath accumulate within the optic nerve.This diffusion of material results in optic nerve dysfunction. Clinically, the loss of optic nerve function may result in loss of visual acuity, visual field defects, color vision defects, and RAPD. In some cases the optic disc is swollen because of infiltration of the prelaminar or immediate retrolaminar region.An absence of disc swelling, with visual acuity loss, may occur secondary to infiltration of the retrolaminar portion of the nerve, which causes a retrobulbar optic neuropathy.

Etiology

Infiltration of the optic nerve most often occurs from autoimmune inflammatory processes or tumor. Common infiltrative sources include sarcoidosis, SLE, leukemia, lymphoma, and primary tumors of the optic nerve.

Sarcoidosis is a multisystem granulomatous disease of unknown etiology characterized by the deposition of noncaseating granulomas surrounded by lymphocytes. The infiltrative optic neuropathy in sarcoidosis may be the first and only ocular sign or may occur in conjunction with other ocular manifestations of sarcoidosis such as uveitis, candle-wax drippings (exudates around the retinal vessels), and choroidal granulomas. Optic disc edema