Optic Nerve Carotid Artery

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If the affected pupil dilates as well or better than its contralateral partner, the site of damage lies somewhere below the level of the ganglion cervicale superius, i.e., in the first- or second-order neurons of the sympathetic pathway.

Lower concentrations of phenylephrine (about 2%) are well suited to the pharmacologic detection of weakened pupillary dilators. Among infants, one often finds an aniso-coria with normal pupillary light reactions and no ptosis that persists after instillation of topical cocaine. If the an-isocoria persists after instillation of 2.5% solution of phenylephrine, it can be concluded that the dilator of the smaller pupil is probably hypoplastic. This is a benign disorder not associated with any other abnormalities of anterior segment development, and it commonly normalizes with the passage of time.

Unilateral or Bilateral Disturbances of Pupillary Light Reactions

Testing the Near Reaction

The near reaction must be tested when there is a unilateral or bilateral abnormality of the pupillary light reaction.

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It should be kept in mind that the pupils of children and younger adolescents frequently do not react until the distance between eye and object of regard is very short (about 10 cm).

There are no documented reports of an isolated loss of the pupillary near reaction. An exception may be the pupillary disturbances found associated with botulism or diphtheria, in which accommodation and the pupillary near response are significantly more affected than is the light reaction. Nonetheless, the pupillary light response is not normal in this setting.

When testing the pupillary near reaction, the level of illumination should be bright enough that the pupils can be easily seen, and an object with fine surface detail (to encourage accommodation) is slowly brought toward the eye.

Definition

Pupillary testing results most often show that the light and near reactions of the pupil are equally impaired or preserved. In some cases, the near response will be found better preserved than the reaction to light. The latter state is called light-near dissociation.

Oculomotor Testing

A monocular defect in the light response of the pupil raises the question of a third nerve paresis (see Chap. 10), while bilateral deficits can be associated with vertical gaze palsies, such as in Parinaud's syndrome (see Chap. 11).

Slit-Lamp Examination

The slit lamp allows close examination of the anatomy of the pupil and iris, particularly with respect to evidence of sphincter atrophy or traumatic disruption. The examiner should note whether the sphincter shows spontaneous movements, whether a strong light stimulus produces a correspondingly large response of contraction, whether some segments of the sphincter move more strongly than

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do others, and whether spontaneous, pathological vermiform movements are present. If the pupil does not appear to respond to a light stimulus, its near response can be tested at the slit lamp. In addition, segmental pareses (causing odd-shaped pupils) and vermiform movements (tonic pupils) are easily seen through the slit-lamp instrument. The slow redilation of a constricted pupil seen at the slit lamp also helps to confirm the tonic behavior of an Adies pupil.

Testing with Pilocarpine 1% and 0.1%

Testing with weak (0.1%) pilocarpine is useful when the diagnosis of a tonic pupil is suspected but not clearly confirmed at the slit lamp. The tonic pupil has a characteristic denervation hypersensitivity to a cholinergic stimulus, which can be associated with Adie's syndrome or a paresis of the oculomotor nerve. Use of the weaker concentration of pilocarpine should always be done first if there appears to be an absolute pupillary paralysis (no response to either light stimulation or prolonged accommodative effort). An immobile, circular pupil at a mid-dilation position is often present in the early stages of Adie's tonic pupillary syndrome.

Testing with weak pilocarpine can be affected by the state of the corneal surface permeability. All testing that can be expected to change the permeability (e.g., tonome-try) should be done after the weak pilocarpine test.

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Testing with the higher (1%) concentration of pilocar-pine is indicated when light, maximal accommodative effort, or weak pilocarpine will not cause the pupil to constrict. If the higher concentration of pilocarpine fails to constrict the pupil, there is a problem within the iris/pupil itself. If an anticholinergic drug (such as atropine or scopolamine) has produced a pharmacologic dilation, the test with 1% pilocarpine is the one reliable way of proving a drug-induced mydriasis. The test is considered positive if the pupil fails to react at all, or responds only minimally. In cases of doubt, the test can be repeated in the contralateral eye to help clarify the diagnosis. In cases of oculomotor paralysis, for example, 1% pilocarpine will reliably cause pupillary miosis, assuming that there is no prior history of injury or surgical manipulation of the iris.

Common Pupillary Syndromes and Their Diagnoses

Horner's Syndrome Definition

Horner's syndrome is a monocular loss of sympathetic innervation to the eye. This causes a loss of function in all of the ocular structures that are sympathetically controlled. The pupil is smaller, but the light reaction remains normal. In 90% of cases, there is a ptosis of the upper lid, caused by paresis of Muller's smooth muscle within the palpebral levator muscle complex. At the same time there is a small elevation of the lower lid as well, since the lower lid retractors are also sympathetically innervated. The narrowing of the palpebral fissure causes the appearance described as "apparent enoph-thalmos." If the site of damage to the sympathetic path lies proximal to the branching of the fibers that mediate sweating and temperature regulation in the face, these functions will also be impaired. The face will appear flushed on one side, with a sharp dividing line that runs precisely along the sagittal midline.

If it is available, instillation of hydroxyamphetamine can help to localize the site of damage more precisely (see above). This allows for a more systematic approach to the diagnosis. ■ Figure 5.4 diagrams the complex pathway of sympathetic innervation of the eye. The principle of further testing of Horner's syndrome is to look for findings in anatomically neighboring structures that help to fix the localization and pathogenesis of the damage. Neurological deficits in brainstem function that accompany Horner's syndrome suggest a proximal site of damage, while symptoms or signs related to the brachial plexus or thorax indicate a more distal site of damage. Brainstem disease can also lead to abnormal eye movements, changes in the vestibulo-ocular reflex, and nystagmus. The regions implicated by such findings should be imaged by CT or MRI scanning. Referral to an appropriate service for investigation of suspected mediastinal or cervical disease may be indicated, but the ophthalmologist should first inspect and palpate the soft tissues of the neck to rule out a large goiter, which is usually easy to detect.

Fig. 5.4. Course of the peripheral sympathetic supply to the pupil and to Muller's muscle. The most common lesions affecting these regions are 1 brainstem stroke, 2 syringomyelia, 3 prolapsed intervertebral disc, 4thoracic outlet syndrome, 5 mediastinal tumors, 6 Goitre, 7 dissecting carotid aneurysm, 8 carcinoma of the paranasal sinuses, 9 tumors of the cavernous sinus, and 10 cluster headaches

Autonomic innervation of the eye

Optic nerve (II)

Oculomotor nerve (III)

Ciliary muscle Pupillary dilator Pupillary sphincter

Accessory nucleus (Edinger-Westphal) of the oculomotor nuclear complex

Long ciliary nerve Nasociliary nerve Maxillary sinus

Trigeminal ganglion Internal carotid plexus Internal carotid artery

Superior cervical ganglion of the sympathetic chain

Optic nerve (II)

Oculomotor nerve (III)

Accessory nucleus (Edinger-Westphal) of the oculomotor nuclear complex

Thoracic spinal cord

Thoracic ganglion of the sympathetic chain

White (myelinated) communicating ramus -

Grey (myelinated) communicating ramus

Ciliospinal center (Budge)

Ciliospinal Center Budge

Trigeminal ganglion Internal carotid plexus Internal carotid artery

Superior cervical ganglion of the sympathetic chain

Sympathetic pathways

1st neuron 2nd neuron -------3rd neuron (peripheral)

Parasympathetic pathways

Preganglionic Postganglionic

Thoracic spinal cord

Thoracic ganglion of the sympathetic chain

White (myelinated) communicating ramus -

Grey (myelinated) communicating ramus

Ciliospinal center (Budge)

Table 5.2. Recommended workup for cases of Horner's syndrome

When preganglionic pharmacologic testing is positive:

• Evaluation by an internist and a neurologist, and neuroradiologic evaluation for cases in which there are additional signs and symptoms

When postganglionic pharmacologic testing is positive:

• If the problem is isolated and not acute, seek a history of cluster headaches or migraine

• When additional cranial nerves are involved, or the problem is acute, refer for MRI or CT

When the problem is congenital or infantile:

• Rule out neuroblastoma

It is possible for malignant disorders to present initially as Horner's syndrome, but the usual causes are much more commonly benign or indeterminate. It is advisable to limit the extent of diagnostic testing and to keep the patient under observation when the initial steps in the evaluation have failed to detect a cause (■ Table 5.2). Monitoring of the patient's findings for changes in signs or the onset of additional symptoms is recommended. Any significant change should be cause for a renewed attempt at localizing the site of damage, since there are disorders that can respond to interventional treatment.

Note

It is important, however, to keep in mind that acute and painful onset of Horner's syndrome is the classic presentation of a carotid artery dissection of the carotid artery, which can occur spontaneously or after minor trauma. It has been associated at times with chiropractic manipulation of the neck. The risk of stroke in these patients is very high, and correct management involves immediate anticoagulation. Patients with this syndrome are commonly tall and slender people, and there is an association with connective tissue disorders like Ehlers-Danlos syndrome.

A singular form of Horner's syndrome is the congenital or infantile onset. Hydroxyamphetamine testing is not usually helpful, since trans-synaptic degeneration can affect the third-order neuron, even though the lesion may lie upstream in the first or second-order neurons. In such cases, the drug may not cause pupillary dilation. In addition, there is usually a visible heterochromia iridis, since development of the iris pigmentation requires an intact sympathetic innervation. The affected eye appears bluer. In addition, in adults with Horner's syndrome, depigmentation of the iris can occur over a period of years.

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The cause of Horner's syndrome in children is most commonly birth trauma. Another less common but more dangerous cause is neuroblastoma, which should be specifically ruled out.

Tonic Pupil Syndrome Definition

Tonic pupil syndrome is a usually monocular loss of parasympathetic innervation of the eye. The site of damage is at the ciliary ganglion or in the short posterior ciliary nerves.

The tonic pupil presents a frequent diagnostic problem, since it is common and does not have a single, typical appearance. It commonly leads to extensive diagnostic testing that fails to identify the source and causes the patient considerable anxiety. Once the diagnosis has been correctly established, further testing is only occasionally necessary.

Most commonly, the affected patients are women between 30 and 40 years of age. However, it can occur at any age. In a few cases, the cause can be established, or at least confidently suspected, e.g., after orbital trauma, extensive panretinal photocoagulation, outbreaks of varicella zoster, orbital ischemia with active giant cell arteritis, and only rarely associated with a malignancy and a suspected para-neoplastic syndrome.

Typically, though, the tonic pupil is harmless. In most instances it is idiopathic (has no identifiable cause). It is frequently associated with a loss of deep tendon reflexes (Adie-Holmes' syndrome), or less commonly with sudo-motor disturbances (Ross syndrome) or with vascular disease. None of these idiopathic types of tonic pupil is so severe as to cause the patient significant loss of visual function.

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Responses

  • Kaija
    Where is the carotid artery in respect to optic nerve?
    6 years ago
  • millar
    Is adies pupil dangerous?
    5 years ago
  • bernardo
    What is by the optic nerve and corotid artery?
    7 days ago

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