Ординатура / Офтальмология / Английские материалы / Handbook of Pediatric Neuro-Ophthalmology_Wright, Spiegel, Thompson_2006

may be something as simple as a need for attention or a desire for glasses or may be as complicated as a presenting symptom of child abuse or of a psychiatric disorder.

Testing Methods

There are many ways to assess the visual acuity of a patient with suspected functional visual loss.9,15 It is not necessary that all these tests be utilized; rather, learn a few tests and learn to use them well. The testing methods can be classified into four different categories: (1) observation, (2) indirect measurement of visual acuity, (3) direct measurement of visual acuity, and (4) supportive findings. Following the discussion of the testing techniques, the best tests for a given patient presentation are recommended.

Observation of the patient with binocular blindness or decreased visual acuity can be very helpful. A truly blind person will bump gently into things; a patient with functional visual loss will either avoid the object or strike the object in an exaggerated manner. The patient’s attitude toward his blindness may also support the diagnosis of functional visual loss.

Pupillary function testing is one of the most useful indirect measures of visual function. Intact, direct, and consensual pupil responses exclude severe and moderate unilateral or asymmetrical visual pathway disorders anterior to the chiasm. Conversely, an afferent pupillary defect clearly supports the claim of a patient with monocular blindness or decreased acuity.

An optokinetic nystagmus (OKN) drum can be utilized to demonstrate visual function. However, some patients can suppress the OKN reflex. A better test utilizes a large mirror placed very close in front of the patient’s face. The mirror is then slowly rocked back and forth (Fig. 12-1). This visual stimulus is almost impossible to suppress if the mirror is large enough to prevent the patient from looking around it. The examiner should observe the patient’s eye following the movement of the mirror from above. If the patient can see, the eyes will move in the same direction as the rocking mirror. A ridiculous facial expression or humorous cartoon may also trick the child into making some sort of response.

The 4-prism diopter base-out prism test is very useful for the patient complaining of monocular blindness. In this test, the prism is placed base out in front of the suspect eye. The normal response is a rapid saccade of both eyes to the side opposite the

FIGURE 12-1. Use of the rocking mirror test in a patient with suspected functional visual loss.

prism, followed by a convergence movement of the uncovered eye 1 to 2 s later. The prism is then placed in front of the good eye as a control. Observing a saccade with the prism in front of the suspect eye rules out acuity less than light perception on that side. Absence of a response suggests but does not prove an organic problem.

A normal response to the Worth four-dot test rules out monocular blindness. Even more useful is stereo-acuity testing. The Wirt circles are large enough to be readable by patients complaining of monocular or binocular decreased visual acuity. The patients do not realize that a stereo-acuity of 40 arc seconds correlates with 20/20 visual acuity in both eyes.23

The last indirect measure of visual acuity is visual evoked response (VER) testing. A recordable response to a flash stimulus rules out absolute blindness of the suspect eye. A correlation also exists between check size and level of visual acuity. Unfortunately, some patients can consciously suppress the response to pattern reversal stimulation. An electroretinogram should be performed in patients with suspected functional

visual loss before making that diagnosis if they cannot be tricked into reading normally or at least substantially better than initially claimed.

After using indirect measures to assess the patient’s acuity, then proceed with direct measures. Children desiring a pair of glasses will frequently read the 20/20 line through a plano lens. I frequently perform a quick, noncycloplegic retinoscopy to look for significant myopia, astigmatism, or anisometropia. Having ruled these things out, I put up the plano lens with the comment that “this is the lens that is measured to be just right for your eye.” More stubborn children can sometimes be cajoled with a combination of 0.25 sphere and 0.25 sphere lenses back to back in a trial frame. The child is told that this is a “telescope” to improve their vision. Keep in mind that the child’s visual acuity may significantly improve once his parents leave the room.

When testing acuity of a child with suspected functional acuity loss, it is best to start with the 20/10 or 20/15 line and express disbelief that such “large” letters cannot be seen. Slowly move through six 20/20 lines with the instructions that each line is twice as large as the one before. With patience and persistence, the child will frequently read 20/20 to 20/30. Testing the consistency of the visual acuity either with different type targets or by maintaining a constant visual angle at different testing distances is very useful and often shows significant inconsistencies in functional patients.

Fogging techniques can be used to blur the vision of the good eye of patients who present with monocularly decreased visual acuity. Three major methods are used. The first method involves secretly slipping a high plus lens in front of the good eye while rapidly performing a subjective distance refraction of the suspect eye. The patient can be confused by all the activity going on around the suspect eye and not realize that the high plus lens has made the good eye quite myopic. The best acuity obtained by the suspect eye is recorded. As a check, the patient should have the suspect eye occluded and then should have the acuity of the previously fogged good eye recorded.

A second fogging method involves placing two high-power cylinders of equal and opposite sign in a trial frame in front of the good eye. So long as the cylinder axes are parallel, the net lens power lens is plano. As the axes are secretly made nonparallel, a large cylinder power results, fogging the good eye. As the patient is reading the acuity chart, the examiner reaches up and

previous evaluations of the visual loss, results of eye examinations in the past, any history of recent or remote ocular trauma, and any significant past ocular and past medical history. While obtaining the history, observe the affect of the child and their interaction with the parents. Inquiries into the social situation can be obtained after the parents and the child are separated.

The patient with claimed binocular blindness can best be assessed using pupillary function testing and the rocking mirror. The OKN drum is less effective as it may be suppressed. Observation of how the patient navigates in his environment is also very useful. The patient presenting with monocular blindness should be tested using the same techniques with the good eye patched.

Patients with binocularly decreased visual acuity seem to be the most difficult because there is no good eye to fog or to isolate using the vectograph or duochrome tests. Stereo acuity testing is helpful in this situation. Persistent visual acuity testing starting at the bottom of the chart and working upward with use of plano lenses will often give results.

Patients with monocularly decreased visual acuity are best evaluated using the vectograph chart, the duochrome test, or the crossed cylinder fogging technique. Some intelligent patients can be observed intermittently closing the suspect eye to prevent the examiner from secretly fogging the good eye. Computerized video acuity testers utilizing high-speed liquid crystal shutter glasses are often helpful in this particular situation. As mentioned, any patient thought to have functional visual loss who cannot be tricked into reading normally should have a normal electroretinogram before making the diagnosis of functional visual loss.

Differential Diagnosis

The major factor to be ruled out in the pediatric age group is amblyopia. The ocular examination must show that strabismus, media opacities, bilateral ametropia, or anisometropia are not present. Keratoconus should be diagnosed by retinoscopy, although keratometry is also helpful. Retinal and macular dystrophies also may present with bilateral acuity loss, or sometimes as monocular acuity loss if the process is asymmetrical. A normal electroretinogram with normal scotopic, photopic, and flicker waveforms rules out these possibilities.

Treatment

Once normal visual acuity in the suspect eye(s) has been documented, one must decide what to tell the patient and what to tell the parents. If the patient wanted a pair of glasses, reassurance that the eyes are normal and that she sees excellently without glasses is all that is necessary. Patients with less identifiable secondary gain should also be reassured. A 1-month trial of multiple vitamins often will allow the patient to give up her functional behavior. Patients with claimed significant visual acuity loss, who do not improve, can frequently be cured with retinal rest.15 This test involves hospitalization with bilateral eye patching. No radio or television is allowed, and visitors are kept to an absolute minimum. The patient’s visual acuity nearly always becomes normal within 2 to 3 days. Psychiatric consultation is frequently helpful in this situation as well.

HEADACHES

Children are frequently referred to ophthalmologists for evaluation of headaches despite the admonition that the eyes are infrequently the cause of headaches. It seems that some pediatricians refer children with headaches to the ophthalmologist to make sure that the eyes are not the cause of headaches before proceeding with a more detailed evaluation. Possible ocular causes of headaches include significant hyperopia, anisometropia, a poorly controlled heterophoria or intermittent heterotropia, convergence insufficiency, and accommodative insufficiency. Ocular disease including glaucoma, uveitis, and corneal disease may give rise to eye pain that may be described as a headache. If ocular examination can rule out these conditions, the search should lead elsewhere.

The difference between a successful and an unsuccessful headache evaluation depends on the history. The headaches should be described as to frequency, duration, severity, location at onset, exacerbating or precipitating factors, and associated signs and symptoms. The patient’s past medical history is important, as is a family history of migraine headaches. Using the history, one should attempt to classify the headaches as (1) an acute single episode, (2) acute recurrent episodes, (3) subacute, and (4) chronic.20

Etiologies

ACUTE SEVERE HEADACHE

The child presenting with the first episode of an acute severe headache poses somewhat of a diagnostic dilemma. These patients usually present to the Emergency Room and do not initially see the ophthalmologist. Possible causes include (1) intracranial processes such as meningitis, encephalitis, or bleeding from an arterovenous malformation; (2) extracranial causes such as sinusitis or head trauma; (3) systemic diseases such as vasculitis or hypertension; (4) environmental causes such as solvent or lead exposure or hypoxia; (5) assorted causes including hypoglycemia or ingested medications; and (6) the first episode of a migraine headache. Evaluation, generally done in the Emergency Room, includes an adequate history, appropriate laboratory studies, and probably CT scan followed by lumbar puncture. Although headaches are rarely caused by hypertension, children with hypertension frequently complain of headaches that are made worse by stooping or lifting heavy objects.

MIGRAINE HEADACHES

Children presenting with acute recurrent episodic headaches generally have migraine. One should keep in mind that migraine describes a spectrum of disease that includes visual auras, anorexia, nausea, vomiting, and sensitivity to noise and light. Headache is the most commonly considered symptom, but is not necessary to make the diagnosis of migraine.28

Migraine can be classified as common, classic, and complicated.34 Common migraine begins with a poorly defined prodrome of psychic or gastrointestinal disturbances, which precede the attack from hours to days; there are no premonitory visual symptoms. The headache usually begins unilaterally but often spreads to involve the entire head. Nearly all patients have nausea; vomiting occurs frequently, and may signal the end or exacerbation of the attack. The duration of the headache is variable and ranges from several hours to several days. About 80% of patients have a family history of common migraine.84

Classic migraine describes a well-defined syndrome, which begins with a visual aura or other sensory disturbance and is fol-

lowed by an intense, pounding headache. The episodes of classic migraine are shorter than those of common migraine and tend to last 2 to 4 h although occasionally longer. The visual aura of classic migraine has been well described.6,27,28 It consists of scintillating lights surrounding a scotoma, which begins near central fixation and then gradually expands to move into the peripheral visual field and away from central fixation. The scintillations surrounding the scotoma often form angled lines that mimic the appearance of fortifications around a medieval town; hence the name fortification scotoma.21 The pathophysiology of the migraine scotoma is thought to be a wave of activation, which is generated in the occipital cortex after the initial event of ischemia secondary to vasoconstriction. This wave of activation starts at the macular occipital pole and then gradually spreads anteriorly to the cortex that represents the peripheral visual field. Children may find it difficult to describe their visual symptoms, but often do have visual impairment, or binocular scotomas. Children may also have visual field defects, distortions of vision such as micropsia, an impairment of time sense, or even hallucinations.12

Complicated migraine describes migraine with associated neurological phenomena that are generally transient but can occasionally become permanent. This group includes cerebral migraine, ophthalmoplegic migraine, retinal migraine, and migraine equivalents. Patients with cerebral migraine may have hemiplegia, hemianopia, sensory defects, and even aphasia. Ophthalmoplegic migraine is particularly common in children and usually starts before the age of 10 years. The oculomotor nerve is most commonly involved, followed by the abducens and trochlear nerves. The term retinal migraine should probably be expanded into anterior visual pathway migraine to describe a monocular visual disturbance accompanying an episode of migraine or in a patient with a strong history of migraine. The key distinction in this case is the monocular nature of the visual disturbance. Anterior visual pathway migraines do not have a preceding fortification spectrum, are not associated with headache, and rarely last more than 10 min. Migraine equivalent describes episodic conditions that are believed to be migrainous in origin but do not have the typical headache history. The most common example in children is abdominal migraine, which consists of episodic nausea, vomiting, or abdominal pain.

OTHER CAUSES OF RECURRENT HEADACHES

Recurrent headaches, very similar to migraine, can be associated with preceding head trauma. The head trauma does not have to be severe or associated with loss of consciousness. Patients with a seizure disorder may complain of postictal headaches; this usually does not cause diagnostic confusion. Additional causes of recurrent headaches include episodes of elevated intracranial pressure from intermittent hydrocephalus or small recurrent subarachnoid hemorrhages from aneurysms or arteriovenous malformations.

SUBACUTE HEADACHES

Subacute headaches are headaches of moderate intensity that have been present for days to weeks. The head pain is present nearly all the time, although exacerbations of severe, intense pain are frequent. Because most of these headaches are associated with elevated intracranial pressure, the headaches are often progressive. It is very important to recognize the patient with the subacute headache, as they usually have a life-threatening or vision-threatening process as the cause of the headaches. The two basic causes are (1) expanding intracranial tumor or subdural hematoma and (2) pseudotumor cerebri.

Fifty percent of patients with an intracranial mass lesion consider headache to be their chief complaint.26 The headache results from traction on pain-sensitive structures within the skull. The headache has a nonthrobbing quality and is worsened by physical activity. Like migraine headaches, the headache often has associated nausea and vomiting. The sudden exacerbations are an important finding. More than half of children with brain tumors are awakened from sleep by their headache. The intracranial mass lesion produces papilledema; focal neurological signs are frequently present. Thus, any child with papilledema or focal neurological sings must have a CT or MRI scan of the head immediately.

Pseudotumor cerebri has an ophthalmoscopic picture nearly identical to the patient with an intracranial mass lesion, the only difference being the lack of focal neurological signs. Four criteria are required to make the diagnosis of pseudotumor cerebri: (1) increased intracranial pressure, (2) normal to smallsized ventricles on CT scan, (3) normal cerebrospinal fluid composition, and (4) optic disc edema. Patients may also have a sixth

nerve palsy or visual field changes, but with rare exceptions no other focal neurological deficits are present. Pseudotumor cerebri is not rare in childhood and can be associated with an extensive list of conditions including steroid withdrawal, tetracycline ingestion, vitamin A intoxication, dural sinus thrombosis, polycythemia, and systemic lupus erythematosus.3 Unfortunately, many cases occur without an obvious precipitating cause. The headaches are typically moderate to severe in intensity, nonpounding, and may be localized to the frontal area. The children frequently have visual obscurations from the associated disc edema; this often occurs when the child stands up. The child may describe these obscurations as transient blurring of vision rather than visual loss.

All patients with a clear history of subacute headaches need to have a cranial neuroimaging to rule out an intracranial mass lesion. If the scan is normal, a lumbar puncture should be performed to measure the cerebrospinal fluid composition and the intracranial pressure. Patients with an intracranial mass lesion need appropriate neurosurgical intervention. Patients with pseudotumor cerebri need to have any possible precipitating factor removed. The elevated intracranial pressure can be treated with Diamox or Lasix. Steroids can be used in the acute setting, although chronic long-term steroid use often worsens the situation due to the associated weight gain. Repeated lumbar punctures are effective, but have some risk and should be reserved for patients unresponsive to medical therapy. If progressive vision or visual field loss is occurring, surgical intervention is warranted. Ventriculoperitoneal shunting and optic nerve sheath decompression are the methods most commonly used.14

CHRONIC NONPROGRESSIVE HEADACHES

Patients with chronic nonprogressive headaches fortunately do not have lifeor vision-threatening conditions. A long list of potential causes exists. The most important ones are (1) the tension or stress headache, (2) eyestrain, and (3) functional complaints, psychiatric disorders, and school avoidance.

Tension or stress headaches are classically thought to be the result of sustained contraction of muscles in the scalp and neck, which leads to the typical complaints of “tightness” or “head in a vise.” The head pain is dull, diffuse, and nonthrobbing. One may find tenderness in the scalp or neck muscles. Tension is an important precipitating factor. Unfortunately, the distinction