Ординатура / Офтальмология / Английские материалы / Clinical Medicine in Optometric Practice_Muchnick_2007

Pupil pathway anatomy. Parasympathetic innervation.

Afferent Pupillary Light Reflex Pathway

The retinal photoreceptor cells convert light quanta into chemical energy. This visual information passes through the axons of the retinal ganglion cells into the optic nerve, optic chiasm, and optic tracts. These pupillomotor fibers do partially cross in the chiasm, but do not synapse in the lateral geniculate body as the visual afferents do. Instead, they separate from the visual fibers in the posterior tract.

Midbrain Light Reflex Pathway

From the posterior optic tract, the pupillomotor fibers synapse in the pretectal nuclei. Axons of the pretectal nuclei may then either travel anterior to synapse in the ipsilateral Edinger-Westphal nucleus, or they may cross over to synapse in the contralateral pretectal nucleus. A small number of fi- bers cross to synapse in the contralateral Edinger-Westphal nucleus.

Efferent Pupillary Light Reflex Pathway

Preganglionic fibers are axons from the Edinger-Westphal that travel with oculomotor fibers as they exit the brainstem. The pupillomotor fibers then synapse in the ciliary ganglion. Postganglionic fibers pass to the iris through short ciliary nerves and innervate the iris sphincter. This efferent pathway represents the parasympathetic innervation of the iris.

Pupil pathway anatomy. Sympathetic nervous system.

The Sympathetic Pupillary Light Reflex

Afferent stimuli from the cortex terminate in the hypothalamus, and the hypothalamus gives rise to the first neuron of the sympathetic chain. These fibers terminate in the ciliospinal center, the second neuron arises from here to exit the spine at the thoracic trunk. The sympathetic nerves then pass close to the apical lung pleura, and terminate and synapse in the superior cervical ganglion at the base of the skull.

Postganglionic fibers emerge from this ganglion as the third neuron. These fibers travel to the carotid sinus and then enter the globe. These efferent fibers innervate the dilator of the iris.

the light is quickly moved to the other eye, both pupils will once again constrict. The examiner should be sure to have the patient gaze at a distant target and not at the light source. This test is best performed in a dimly lit room (Figure 17-8).

It is best to allow only 3 to 5 seconds of illumination on each side. The examiner should be sure not to force open the lids, because the patient’s attempts to squeeze the lids shut will cause pupillary miosis.

If, when the examiner swings the light from one pupil to another, both pupils dilate instead of constricting, then the stimulated eye is conducting less electrical impulses than the unstimulated eye. These impulses are carried away from the eye by the afferent pupillary pathway (see Box 17-1 and Figure 17-9).

A relative afferent pupillary defect (RAPD) should be graded on a scale of 1 (no constriction) to 4 (brisk dilation). This scale is purely subjective. To objectively

FIGURE 17-5 ■ Pupil measurement with Haab scale.

FIGURE 17-6 ■ Anisocoria greater or unequal pupil size.

FIGURE 17-7 ■ Loss of consensual light reflex.

measure the RAPD, the examiner should hold neutral density filters in front of the uninvolved eye when performing the swinging light test. The filter density should be increased until the pupil reactions on the swing test are equal. This produces an accurate number

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FIGURE 17-8 ■ Swinging light test.

FIGURE 17-9 ■ Relative afferent pupillary defect.

in log units of the size of the RAPD, and can be used in future examinations to see whether the RAPD is changing. This reaction also demonstrates that an artificial RAPD can be created by holding a neutral density filter in front of one eye of a normal patient while performing a Swing Test. The darker filter produces less impulses carried in the afferent pathway compared with the unfiltered eye (Figure 17-10, A and B).

It is possible to confirm the presence of an RAPD when the light defect is so subtle as to be equivocal. In this case, a minimal-density neutral density filter, such as a .3 ND filter, should be used. The examiner should place the filter in front of the uninvolved eye. A swinging light test should reveal equal pupil reactions. However, when the .3 filter is placed in front of the eye suspected of having a subtle RAPD, the reduction of illumination will exaggerate the existing defect and produce a recognizable RAPD. In the normal individual, the .3 filter is not dense enough to produce an obvious artificial RAPD, or if one is produced, it will be equal in both eyes.

B

FIGURE 17-10 ■ A and B, Use of neutral density filters to grade an RAPD.

An RAPD is not related to visual acuity but to the threshold of light perception. Even a dense cataract that significantly reduces vision does not cause an RAPD because of light scattering, except in very rare cases.

The Near Reflex

Once the examiner has tested for the presence of a RAPD, the next step is to test the accommodative system. The patient should be asked to look at a near target while in dim (Figure 17-11) illumination. The examiner should note whether the pupil reacts by constricting. If a poor response is observed, the examiner should tap the patient on his or her own fingertip while the patient looks at it. This usually produces a fairly brisk near response. A sluggish or absent accommodative response should alert the examiner to a possible significant disorder. When the near reflex contraction is greater than the patient’s best light reflex, a light-near dissociation exists and should be considered a pathology.

Next, the examiner should ask the patient to look to a distant target and assess the briskness of the pupil redilation, and note whether the dilation is prompt and brisk, or slow and delayed.

It is not necessary to test the near reflex when the light response is normal, but the near reflex should be tested in all cases of anisocoria.

Pupillary Cycle Times

When a focused beam of a slit-lamp is placed horizontally on the inferior iris and raised so that it just grazes the lower edge of the pupil, miosis will occur because of light entering the eye. The subsequent miosis cuts off light to the retina, causing a redilation. The pupil continues to cycle through mydriasis and miosis as long as the light is held steady on the edge of the pupil. These pupillary cycle times may be reduced in multiple sclerosis, neurosyphilis, and in RAPD. But the test is prone to errors and examiner bias, and the results have thus far been confusing

Recording Pupil Responses

Modern video cameras can be used to record pupil responses. Many of these cameras have a “gain-up” system that allows for high sensitivity in recording pupil responses even in dark irises. This author has found very favorable results using this system to record and measure pupil size and reactions.

The Abnormal Pupil

Anterior Chamber Anomalies

Congenital malformations and anomalies of the iris (Box 17-2) produce eccentric and irregular pupils. Ocular trauma that produces contusion to the globe may produce iris sphincter tears, iridodialysis and cyclodialysis that may displace the pupil and produce an irregular pupillary light reaction. Intraocular inflammation, such as anterior uveitis, may produce iris nodules and anterior and posterior synechiae, all of which may result in an inappropriate pupil shape and movement.

Finally, any abnormal pupil shape, position, or light response may be the result of the presence of an iris tumor. Any iris malformation may act as a diag-

Box 17-2

IRIS ETIOLOGIES OF PUPIL DYSFUNCTION

Iris Pathology as a Cause of Pupil Dysfunction

1.Iris coloboma: congenital absence of iris tissue.

2.Congenital aniridia: congenital absence of all of iris.

3.Persistent pupillary membrane: may cause distorted pupil responses.

4.Progressive essential iris atrophy: atrophy of iris stroma may cause ectopic pupil and distorted pupil responses.

5.Iris tumor: may distort pupil reflexes.

6.Anterior uveitis: may lead to iris nodules and synechiae, thus altering the pupil reflex.

Iris Trauma as a Cause of Pupil Dysfunction

1.Sphincter tear: may look like a coloboma.

2.Iridodialysis: tear of iris from its mooring at the root of the iris. Distorts pupil.

3.Cyclodialysis: tearing of the ciliary body away from the scleral spur, may distort the pupil.

nostic dilemma in the pupil work-up because pupil responses depend on the appropriate iris structure. The asymmetry that is characteristic of anterior chamber anomalies usually produces anisocoria.

Neurologic Anomalies:

Lesion Localization—Anisocoria

The first indication that a neurologic entity may be causing a pupil problem may come with the detection of anisocoria. If this asymmetry in pupil sizes cannot be explained by physical iris changes, then the examiner must consider a neurologic cause.

In most cases of anisocoria no significant cause exists, and this is known as simple, or see-saw anisocoria. It is best seen in dim illumination and it is considered benign. Anisocoria is a significant ocular sign when it is associated with abnormal pupillary reflexes or other significant clinical signs.

Retinal, optic nerve, chiasm, and optic tract lesions do not cause anisocoria. A lesion of the intercalated neuron in the midbrain produces a transient anisocoria that is difficult to observe. Most neurologic causes of anisocoria are the result of lesions in the efferent pupillary pathway (see Box 17-1). These arise because of asymmetric disruptions of the parasympathetic or sympathetic nervous system innervation of the iris. Thus, the presence of anisocoria may help to localize a lesion to this pathway, but not its location in the pathway.

When anisocoria is greater in bright illumination, the dilated pupil is considered to be abnormal until proven otherwise. The differential diagnosis of this dilation includes a self-administered drug, a tonic pupil, or damage to the efferent fibers of the third cranial nerve because of significant and potentially catastrophic intracranial pathology.

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Lesion Localization—The Relative Afferent Pupillary Defect

Neurological problems may cause pupillary problems and yet not produce anisocoria. These will usually produce an abnormal direct or consensual light reflex. Therefore, despite the absence or anisocoria, the examiner should make sure to evaluate direct and consensual pupillary responses to light stimulation.

If an abnormal result is found in this evaluation, it will most often conform to one of the following four observations.

1. A normal, brisk, direct response is seen in the tested eye, but a reduced or absent consensual response in the fellow eye. In this case, the examiner should look for abnormal iris anatomy or pharmacological blockade of the consensual iris. If none is found, the examiner should consider a neurologic problem existing in the consensual eye, most likely in the efferent pupillary pathway.

2. A reduced or absent direct pupillary response to light is seen but a brisk, rapid, consensual response of the fellow eye (Figure 17-12). Again, the examiner should exclude a pharmacological blockade of the stimulated eye or abnormal iris anatomy. If none is found, the examiner should consider a neurologic cause affecting the stimulated eye, most likely in the efferent pupillary pathway.

3. Direct stimulation of one eye results in constriction of both pupils, but stimulation of the fellow eye produces bilateral pupil dilation (Figure 17-13). This response becomes more obvious when the swinging light test is performed and will confirm the presence of a RAPD in the stimulated but poorly reacting eye. This is most likely the result of a neurologic lesion in the afferent pupillary pathway of this eye or in the contralateral optic tract.

4.You may find that both the direct and consensual responses are abolished when either eye is stimulated

FIGURE 17-12 ■ Negative direct response with positive consensual response.

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FIGURE 17-13 ■ Positive direct and consensual response but negative response in fellow eye.

(Figure 17-14). In this case, the examiner should make sure that the patient did not insert dilating or constricting drops in both eyes, causing a bilateral pharmacological blockade. If not, the examiner should use the slit-lamp to exclude iris abnormalities that may cause bilateral pupil defects. If no problems are found, then the examiner should seriously consider a neurologic lesion of the midbrain or the efferent pupillary pathways of both eyes. A bilateral afferent pupillary defect may also produce this result.

Pupillary Disturbances Caused by Neuroophthalmic Disease

Disease processes affecting the pupillary light reflexes may be classified into the following three categories, according to the anatomical location of the lesion.

1. Lesions of the afferent pupillary pathway (which carries impulses away from the retina).

2. Lesions of the midbrain (the interconnections).

3. Lesions of the efferent pupillary pathway (which carries impulses to the iris).

FIGURE 17-14 ■ No responses when either eye is stimulated.

Diseases of each of these three areas can cause characteristic pupillary reflexes that can aid in localization and diagnosis of the lesion.

Lesions of the Afferent Pupillary Pathway

The afferent pupillary pathway consists of the retina, optic nerve, optic chiasm and optic tract. In general, lesions of these structures are usually unilateral or asymmetric and so produce an RAPD. Lesions of the retina and optic nerve produce an ipsilateral RAPD and a complete transection of the optic tract produces a contralateral RAPD because of unequal crossing of the fibers (Table 17-3).

Retinal Disease

A retinal disease that reduces the retinal functioning of one eye more than the other will interfere with the direct light reflex of that eye. Light stimulation of the affected eye will produce a sluggish, or in the extreme case, an absent, direct reflex in the involved eye and an equally sluggish consensual response in its fellow eye. Light stimulation of the fellow intact eye produces brisk and normal response in both eyes. Significant unilateral or asymmetric retinal pathology may produce an RAPD but, as long as the efferent pupillary pathway is uninvolved, no anisocoria.

It is obvious that pupillary reflexes are not as important as ophthalmoscopy in the determination of retinal involvement, but pupillary dysfunction can serve as a clue that an in-depth evaluation of the retina is mandatory.

Optic Nerve Lesions

Just like retinal lesions, a disorder of the optic nerve causes a disturbance of only the direct light reflex; the consensual reflex (when stimulating the uninvolved eye) remains intact. A swinging light test will demonstrate a RAPD of the affected eye (Box 17-3).

When the optic nerve is completely transected (as in severe trauma), the affected pupil will be unreactive to direct light stimulation. This condition is known as amaurotic pupillary akinesia. No anisocoria is noted in optic nerve disorders as long as innervation to the iris remains intact. The degree of RAPD depends on the extent and location of the optic nerve lesion. The optic nerve lesion may produce clinical symptoms and signs that can be correlated with pupillary dysfunction in an effort to diagnose the disease (Box 17-4).

Optic Chiasm and Optic Tract Lesions

With rare exceptions, lesions of the optic chiasm and tract will not affect the pupillary responses in either eye. However, because lesions of the chiasm and tract can cause visual field defects, very discrete light stimulation of the retinal area corresponding to the visual field loss will produce a reduced pupil response when

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BOX 17-3

WHAT IS A REVERSE RAPD?

A reverse RAPD is best understood by looking at an example. When a light is directed into the right pupil, both pupils constrict. Swinging the light to the left eye causes both pupils to dilate. This movement indicates a left RAPD.

But what if the left pupil cannot react because of a pharmacological blockade or abnormal left iris anatomy? If the left pupil cannot react, is it possible to detect a RAPD? Yes!

Repeat the swing test with a left RAPD and a left pupil constricted and unreactive because of the use of pilocarpine. Direct the light into the right pupil and notice that it constricts. Now swing the light to the left pupil, which does not react because of use of pilocarpine. How can you tell if a left RAPD is present if the pupil can’t dilate? By looking at the right pupil as light is shined into the left eye. If the right eye dilates, this means a left RAPD is present despite the lack of left pupil response. You are looking at the opposite (or reverse) eye than in a normal swing test.

BOX 17-4

SOME OPTIC NERVE CAUSES OF RAPD

Congenital nerve anomalies

Neoplasms

Leber’s optic atrophy

Temporal arteritis

Optic neuritis

Glaucoma

Multiple sclerosis

Trauma

compared with stimulation of the normal visual field area. This effect is known as pupillary hemiakinesia and is difficult to elicit because of light scattering within the eye and the inability to produce a light source discrete enough to stimulate only the affected areas. In theory, a complete transection of the optic nerve would produce a contralateral RAPD because of unequal crossing of the fibers.

Lesions of the chiasm and optic tract do not produce anisocoria unless there is damage to the pretectal decussation and nerves innervating the iris.

Upper Visual Pathway Lesions

The pupillary light reflex was long believed to be unaffected by lesions above the lateral geniculate body (see Box 17-1). Like chiasmal and optic tract lesions, however, pupillary responses will be reduced when areas of visual field loss are stimulated and compared with those areas of normal visual field sensitivity. Again, this test is difficult to perform, thus in practice upper visual pathway lesions will not produce an

RAPD. Upper visual pathway lesions will not produce anisocoria.

Lesions of the Midbrain (The Interconnections)

In the pretectal area, the intercalated neurons send equal numbers of pupillomotor fibers to each side so that the two pupils constrict equally. However, anisocoria may develop from midbrain lesions when hemidecussation of fibers from the pretectal neurons to the oculomotor nuclei is interrupted. Lesions of the midbrain can produce the Argyll Robertson syndrome and Parinaud’s syndrome.

Argyll Robertson Syndrome

The patient with Argyll Robertson syndrome is seen with bilateral miotic pupils. On closer examination, these miotic pupils are seen to be irregular and spastically contracted. These pupils do not react to light but constrict briskly to accommodation.

The lesion would have to be located in the midbrain and affect the interconnections between the two pretectal nuclei and two Edinger-Westphal nuclei. The lesion causes an interruption of supranuclear inhibition, thus yielding miosis. The miosis is asymmetric, and so anisocoria is almost always present.

Accommodation in Argyll Robertson syndrome remains unaffected, because accommodative fibers take a different (and thus uninvolved) pathway. Because the light reflex is absent but accommodative miosis is normal, this reaction is known as a light-near dissociation (LND) pupil. The most common cause of Argyll Robertson syndrome is neurosyphilis (Box 17-5).

Examination of the patient who is seen with Argyll Robertson pupil is best performed in dim illumination, because this will enhance the anisocoria. In addition to the near response being brisk, the redilation is also quick as compared with a tonic pupil which has a characteristic slow redilation.

Discovery of a patient with Argyll Robertson syndrome mandates a work-up for syphilis.

Midbrain Tumors

LND pupils may also occur because of midbrain tumors such as pinealomas, astrocytomas, and meningiomas. These lesions interrupt the connections between the pretectal nuclei and the Edinger-Westphal

BOX 17-5

CAUSES OF ARGYLL ROBERTSON SYNDROME

Neurosyphilis

Trauma

Tabes diabetica

Multiple sclerosis

Neoplasm

Encephalitis

nuclei. Unlike the Argyll Robertson syndrome, however, these lesions produce bilateral oval mydriasis with anisocoria.

Pineal tumors can cause bilateral dilated pupils that are unresponsive to light and are accompanied by a vertical gaze palsy, accommodative weakness, and nystagmus on attempted upward gaze. This constellation of clinical signs is known as Parinaud’s syndrome.

Lesions of the Efferent Pupillary Pathway

The characteristic sign of an efferent pathway defect is anisocoria. Efferent pupillary pathway problems may result from lesions of the parasympathetic pupillary fibers or interruption of the sympathetic pathway.

Parasympathetic Pupillary Fiber Lesions

These lesions are differentiated on the basis of whether the lesion affects the parasympathetic (constricting) impulses at the oculomotor nerve nucleus (preganglionic, or first neuron) or further on at the ciliary ganglion nucleus (postganglionic, or second neuron). In either case, both pupillary light reflex and accommodation are impaired.

Efferent Third-Nerve Deficits

Complete third-nerve palsy will result in total ophthalmoplegia with the characteristic signs of an eye that is “down-and-out,” with complete unilateral ptosis and a fixed, dilated pupil. Paralysis of the superior rectus, inferior rectus, medial rectus, and inferior oblique muscles is present, with loss of adduction and superior and inferior gaze. Accommodation is also lost, as well as the near light reflex.

The dilated pupil is fixed, despite light stimulation of the fellow eye. This sign differentiates this pupil from pretectal involvement, which reduces the consensual reflex alone and not the direct response.

A fixed, dilated pupil should always be considered a sign of significant and catastrophic disease such as tumor, aneurysm, infection, and intracranial hemorrhage. The examiner should look for associated neurologic signs, but if inadvertent pharmacological installation or a mydriatic is suspected, he or she should confirm it by instilling 0.1% pilocarpine and then 1% pilocarpine drops in the eye. Dilute pilocarpine will not constrict a pharmacologically blocked pupil.

Sites of Third-Nerve Damage

Nuclear Lesions

Because the Edinger-Westphal nuclei are so close together, these rare deficits are usually bilateral with involvement of all extraocular muscles and loss of accommodation. The causes of nuclear third-nerve lesions include tumors, infections, multiple sclerosis, and vascular accidents.

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Fascicular Lesions

The fibers from the nucleus to the interpeduncular fossa are spread out so the effects are usually partial with pupil effects associated with contralateral hemiplegias or ataxias.

Basal Lesions

Third-nerve damage close to its emergence from the brainstem causes a partial oculomotor deficit with pupil dilation and may result from subarachnoid hemorrhage. For this reason, a dilated pupil is of grave concern.

Cavernous Sinus

Tumor, infection, inflammation, or intracavernous aneurysm may cause involvement of cranial nerves III, IV, V, and VI, as well as the sympathetic pupillomotor fibers. This causes a pupil that is smaller in darkness (because of loss of the sympathetic fibers) and larger in bright light (because of loss of the third nerve). Associated pain and anesthesia of the face are present.

Orbital Third-Nerve Lesions

Trauma, tumor, aneurysm and infection from a tooth abscess can cause vision loss, RAPD (if the afferents are involved), parasympathetic, and sympathetic involvement.

The Tonic Pupil

Postganglionic, or second-neuron, lesions occur anywhere from the ciliary ganglion to the eye. A lesion affecting these parasympathetic fibers causes anisocoria with a larger pupil that reacts poorly to both light and accommodative effort. This condition is known as a tonic pupil. It is more obvious in bright illumination, because in dim illumination both pupils may appear to be equally dilated. The tonic pupil may demonstrate a distorted pupil shape and a bizarre, irregular, and slow contraction and redilation to light stimulus.

The lesion that causes this pupil is most likely located in the ciliary ganglion, which causes the eye to be hypersensitive to dilute cholinergic agents (Table 17-4). When a tonic pupil is of unknown cause, it is termed an Adie’s syndrome. It may be accompanied by loss of the deep tendon knee reflexes. Serologic testing should be performed to exclude syphilis in cases of Adie’s tonic pupil (see Case Report: A Case of Bilateral Adie’s Tonic Pupil in this chapter).

In the tonic pupil the ciliary ganglion is damaged, usually because of an obscure etiology. Most of the neurons die, causing a loss of accommodation and pupil dilation. The surviving neurons send new axon sprouts to the eye. This reinnervation is diffuse, and irregular link-ups cause wormlike contractions of the pupil known as vermiform (wormlike) movements.

If pain is associated with a tonic pupil, then the patient should be tested for an intracranial lesion or orbital mass. Dilute pilocarpine, 1⁄16% will constrict a tonic pupil but not a normal pupil.

Sympathetic Pupillary Fiber Lesions

A lesion of the sympathetic innervation to the iris dilator produces a miotic pupil. In addition, loss of sympathetic innervation to the upper lid produces a ptosis. This combination of ptosis and miosis is characteristic of Horner’s syndrome. The unilateral miosis produces anisocoria, which will be greatest in dim illumination, because bright light will make both pupils appear constricted. No loss of accommodation is present. There are numerous causative processes of Horner’s syndrome (Box 17-6).

To determine the etiology of Horner’s syndrome the examiner must first determine the location of the lesion. Interruption of the sympathetic pathway to the iris may occur between the hypothalamus and spinal cord (central, or first neuron), between the spinal cord and superior cervical ganglion (second neuron), and between the superior cervical ganglion and the iris (third neuron).

Firstand second-neuron Horner’s syndromes are considered preganglionic, and third-neuron Horner’s syndrome is postganglionic.

Differentiating preganglionic from a postganglionic Horner’s syndrome begins with the determination of sweat pattern distribution. Brainstem (first neuron)

BOX 17-6

PERIPHERAL CAUSES OF HORNER’S SYNDROME

Neck trauma

Goiter

Neck surgery

Internal carotid artery

Aneurysm

History of incubation for surgery

Cluster headache

Apical pulmonary tumor

Neoplasms

lesions cause ipsilateral loss of sweat to the face and body (anhidrosis). Sympathetic disruption in the spinal cord produces anhidrosis of half the face and neck. Second neuron involvement produces anhidrosis of the face. Postganglionic fiber disruption in the neck, the base of the skull, and orbit produces anhidrosis of only the forehead.

Drug Responses In Horner’s Syndrome

Pharmacological confirmation of a Horner’s syndrome may be accomplished by the instillation of 4% cocaine drops in the eye. Cocaine will cause mydriasis in the normal eye but fail to dilate the affected eye. (However, in first-neuron Horner’s syndrome, mild mydriasis may occur.) Thus, cocaine can confirm a sympathetic disruption but not localize it.

Because cocaine cannot differentiate preganglionic from postganglionic involvement, Paredrine 1% may be used to isolate the location of the lesion. Paredrine 1% dilates a preganglionic pupil normally but will not dilate a Horner’s syndrome pupil that is the result of postganglionic damage.

Causes of Horner’s Syndrome

Of preganglionic lesions, 50% are malignant in nature and many of the remaining are caused by vehicular “whiplash” injury. Interruption of the preganglionic sympathetic pathway of the second neuron may be the result of a tumor, and an apical pulmonary carcinoma should be excluded.

Most postganglionic (third-neuron) Horner’s syndromes are vascular in nature and many of these patients experience “cluster” headaches (see Box 17-6).

Case Report: A Case of Bilateral Adie’s Tonic Pupil

A 48-year-old white male was seen in our clinic with a complaint of unilateral sudden-onset loss of near accommodation. He had visual acuities of 20/20 in both eyes but loss of accommodation at near in his right eye, with minimal accommodation reduction in his left eye. Anisocoria was present, with his right pupil being larger than his left, and the anisocoria more apparent

in bright illumination. Slit-lamp evaluation demonstrated the right pupil to constrict sluggishly and segmentally to bright light. Consensual response in the fellow eye was normal. The near reflex was much reduced in the right eye. No RAPD was present. Our impression was unilateral Adie’s tonic pupil. The patient was asked to return for pharmacological testing to confirm tonic pupil.

On his return the anisocoria (Figure 17-15) was still present, but both pupils were now sluggish to light and accommodation. Very dilute pilocarpine was applied to both eyes, which caused miosis (Figure 17-16), thereby verifying a bilateral Adie’s tonic pupil. There was a loss of deep tendon knee reflexes on both sides. Serological testing was negative for syphilis.

Case Report: A Case of Inadvertent Mydriatic Instillation (Pharmacological Blockade, or, How Knowing a Little Too Much Can Hurt)

A 32-year-old nurse was seen in our clinic in a near panic because of a unilateral dilated pupil. She denied any history of trauma and denied instillation of eye drops. Visual acuities, confrontation fields, extraocular

FIGURE 17-15 ■ Adie’s tonic pupil: anisocoria. Case report.

FIGURE 17-16 ■ Adie’s tonic pupil: dilute pilocarpine test. Case report.

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muscle motilities, and external and internal examination were normal. Direct light stimulation of the involved eye failed to produce any constriction but did result in normal miosis of the consensual eye.

Because the day of her visit was a Monday, I asked her what she had done over the weekend. She replied that she had gone sailing. Asked whether she had gotten seasick, she replied she hadn’t because she wore a transdermal patch to prevent seasickness (bingo!).

The patch contains scopolamine, which is a potent dilator. At some point she had touched her eye and caused dilation of the pupil. One drop of 1⁄12% pilocarpine was instilled in the eye and failed to constrict the pupil, so no hypersensitivity was present. Pilocarpine 1% also failed to constrict the pupil, thus confirming a pharmacological blockade.

This case demonstrates that history is as significant as any pupil testing in determination of etiology of a pupil dysfunction.

Ocular Motility Dysfunction

The refinement of binocular vision has been a critical development in the course of human evolution. The ability to place an image of interest on both foveas simultaneously and in all positions of gaze must occur in spite of head movement or object motion. Without a means to counteract even the subtlest of head movements, images would sweep across the retina, causing degradation of visual acuity. Even the tiniest of head vibrations because of cardiac pulsation would blur vision if no compensatory mechanism were present.

This chapter is divided into two sections. The first part deals with the supranuclear motility system, its anatomy, examination, and disease processes. The second section reviews the infranuclear motility system, which comprises eye movements generated by the third, fourth, and sixth cranial nerves.

The Supranuclear Motility System

Four general classes of eye movements are known as supranuclear ocular motility systems. These movements stabilize retinal images and are defined by the specific stimulus needed to initiate the given movement, and a description of the type of movement elicited.

The first of these eye movements, the smooth pursuit system, acts to hold the image of a moving target on the fovea. Another one, the saccadic system, directs both foveas toward the image of regard. The vestibularoptokinetic movements act to hold the images of the visualized world steady on the retina during head rotation. Finally, the vergence system acts to move the eyes in opposite directions so that images of a single object in space are placed simultaneously on the fovea.

These complex supranuclear eye movements take the coordinated efforts of whole muscle groups. No one