Functional Neuro Ophthalmic Conditions.9

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FUNCTIONAL

NEURO-OPHTHALMICCONDITIONSMichael S. Vaphiades, Lanning B. Kline

ABSTRACT

The termfunctionalor nonorganicindicates that the patients visual acuity, ocularmotility, or pupillary impairment has no underlying anatomic or physiologic basis.The diagnosis of a functional syndrome is one of exclusion. This chapter will definethe different types of functional visual disorders and characterize the testing usedto diagnose them.

Continuum Lifelong Learning Neurol 2009;15(4):106120.

INTRODUCTION

The physician-patient relationship is aunique one. The physicians role is toacquire the history, examine the pa-tient, diagnose a disease process, andinitiate treatment. The patients role is

even more difficult, because dysfunc-tion is often accompanied by feelingsof fear of the unknown and loss ofcontrol. The physician and the patientare allies in the achievement of a com-mon goal: identifying the physiologicororganiccause of the disease process.

When the patients reported symptomsare suspected not to be based on anorganic process, the physician-patientdynamic may change from one of tryingto defeat a common enemy (the disease

process) to the physician and patientnow working contrary to one another.

When this occurs, it is crucial for thephysician to remain empathic, lest theoffice visit deteriorate into an adversar-ial event. It is important that the physi-cian discusses the examination findingsand explains their implications to thepatient. In addition, the patient must

always be given a way out or an op-portunity to save face in this very awk-

ward situation.The term functional indicates that

the patients impairment has no un-derlying anatomic or physiologic basis.

Visual complaints that have no physi-ologic or organic basis are also re-ferred to as nonorganic. The terms

functional and nonorganic will beused interchangeably in this text.

Recognition of nonorganic diseasedates back to antiquity. The termhysterical (from the Greek) literallymeans a uterine condition and sug-gests a process unique to women.Plato thought the uterus was endowed

with its own will. If it wandered below

the ribs, it produced hypochondria.In the Middle Ages, if a womans be-havior was unusual in any way, she

was felt to be possessed by a demon,and labeled hysterical (Thompson,1985). In the late 1800s, Charcotdemonstrated that hysteria was notunique to women but also occurred in

men. Charcots students, Freud and

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Relationship Disclosure: Drs Vaphiades and Kline have nothing to disclose.Unlabeled Use of Products/Investigational Use Disclosure: Drs Vaphiades and Kline have nothing to disclose.

KEY POINTS

A When examining

patients with

functional

visual loss, itis crucial for

the physician

to remain

empathetic, lest

the office visit

deteriorate into

an adversarial

event.

A It is important

that the

physician

discuss theexamination

findings and

explain their

implications to

the patient with

nonorganic

symptoms. In

addition, the

patient must

always be given

a way out or an

opportunity to

save face in thisvery awkward

situation.

Copyright # 2009, American Academy of Neurology. All rights reserved.

Copyright @ American Academy of Neurology. Unauthorized reproduction of this article is prohibited.


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Babinski, defined hysteria as a subcon-scious expression of nonorganic symp-toms caused by suggestion and cured

by persuasion. Freud felt that hyste-ria stemmed from emotional distur-bances of sexual origin and that visualloss was a conversion from emotionalto physical manifestations, which re-lieved emotional turmoil; hence theterm conversion reaction. Such hys-terical patients may exhibit la belleindifference or lack of concern regard-ing their symptoms, ie, an emotionalfunctional mismatch (Thompson, 1985).

The term malingering indicates a

willful feigning of symptoms for per-sonal gain, ie, financial or emotionalimprovement. The symptoms of a ma-lingering patient are not psychogenic,for they are dependent on volition;true psychogenic disturbances are in-

voluntary. The economic impact stem-ming from malingering patients isstaggering, costing society millions ofdollars in fraudulent claims (Keltneret al, 1985). Patients with malingeringare aware that their symptoms do notexist, while hysterical patients believethat their symptoms truly exist. An ad-ditional form of functional disorder isthat of factitious disease. In this setting,patients intentionally induce real symp-toms. These patients are often said tohave Munchhausen syndrome. Patients

with Munchhausen syndrome harbora psychological need to adopt the roleof an ill person and therefore manifestfactitious physical symptoms and signs

to fulfill this need (Miller, 2005). Use ofthe terms functional, nonphysiologic,or nonorganic avoids the negativeaspects of terms such as malingering,hysteria, or Munchhausen syndrome,as well as avoids potentially false state-ments expressed to a third party thatmay do harm to a patients reputation.

Functional visual disturbances mayinclude a variety of symptoms. Themost common functional ophthalmo-logic symptom is that of visual loss. In

adults, functional visual loss is morecommon in women. Many patients(over 50% in one study) also have a

concomitant psychological disorder,and care must be taken to separatethe two (Kathol et al, 1983). Examplesinclude somatization disorder, affectivedisorder, anxiety disorder, and variouspersonality disorders such as histrionic,antisocial, schizoid, and passive aggres-sive. Exaggeration of an organic pro-cess as a manifestation of a functionaldisorder is one of the most difficultproblems faced by the physician, as thereal component may make it impos-

sible to demonstrate that the patientsvision is entirely normal. Similarly, the

real component tends to be ignoredonce evidence suggests functional over-lay. As will be discussed, dealing withthe underlying organic problem canoften result in marked improvementof the entire syndrome.

Functional visual loss in children is

estimated to occur at a rate of 1.4 per1000 per year (Brodsky et al, 1996). Itis more commonly seen in girls be-tween the ages of 9 and 11 (Clarkeet al, 1996). As in adults, functional

visual loss in children is a diagnosis ofexclusion. Up to 25% of children with

nonorganic visual loss have a super-imposed organic disorder (eg, maculo-pathy) (Brodsky et al, 1996). Commonassociated symptoms include headaches,diplopia, and micropsia. Functional oc-ular motility disorders, including spasmof the near reflex and voluntary nys-

tagmus, also occur more commonly inchildren.The first requirement for identify-

ing functional visual disorders is a highindex of suspicion. A patients affectmay provide a strong clue to a nonor-ganic process. Patients may be clearlydepressed, indifferent, anxious, hos-tile, or excessively cooperative. Histori-cal inconsistencies in the pattern or

the degree of the visual dysfunctionare often the first clue to a nonorganic

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process. The nature of the history it-self may also provide clues as to mo-tives for secondary gain. The key issue

for the examiner is to assess for in-consistencies between subjective pa-tient concerns and objective findingson clinical examination. The physicianmust be patient, persistent, and fac-ile with the testing techniques used,and the patient must remain unawareof the examiners goal: demonstrat-ing better function (visual acuity, vi-sual fields, ocular motility, etc) thanclaimed. The concept of misdirection(ie, the perceived testing of the nor-

mal eye when in reality the impairedeye is being tested) is important, asthe physician often must employ a cer-tain amount of showmanship andcreativity to achieve this goal. Mostimportantly, the physician must adoptan attitude of empathy toward the pa-tient and avoid confrontation, which

will undermine the goal of the officevisit.

Functional visual complaints canbe separated into four categories: (1)afferent (visual acuity and field), (2)efferent (ocular motility and align-ment), (3) pupil and accommodation,and (4) eyelid position and function.Methods to diagnose each will be dis-cussed separately.

TESTING TECHNIQUES

Functional Disease Affectingthe Afferent Visual Pathway

Testing techniques for functional vi-sual loss are outlined in Table 7-1.

Binocular complete visual loss.Finger touchingis a technique in whichthe patient is asked to touch the fin-

gertips of each hand together. Patientswho are truly blind, or sighted personswith closed eyes, can easily touch theirfingertips together because this requiresonly proprioception, not vision. Patients

with functional monocular blindnessmay touch their fingertips together when

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TABLE 7-1 Testing Techniquesfor FunctionalVisual Loss

" Binocular Complete Visual Loss

Mirror

Finger-touching (Figure 7-1)

Optokinetic nystagmus(Figure 7-2)

Evaluation of ambulation

" Monocular Complete VisualLoss

Swinging flashlight (relativeafferent pupillary defect)

Stereoacuity test

Finger-touching (Figure 7-1)

Optokinetic nystagmus

(Figure 7-2)

Mirror technique

Prism shift and prismdissociation tests (Figure 7-3)

" Monocular Reduced VisualAcuity

Stereoacuity (Figure 7-2)

Prism shift and prismdissociation tests (Figure 7-3)

Polarizing lens test (Figure 7-4)

Duochrome test (Figure 7-5)

Fogging techniques (Figure 7-6)

Bottom-up acuity

Near-distance discrepancies

Electrophysiology(visual-evoked potentials,

electroretinogram)" Binocular Reduced Visual

Acuity

Stereoacuity test

Prism tests

Polarizing test

Duochrome test

continued on next page


"FUNCTIONAL CONDITIONS



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viewing with the normal eye, but notwith this eye occluded (Figure 7-1)(Miller, 2005).Optokinetic nystagmustesting involves an optokinetic nystag-mus drum or tape moved to inducehorizontal jerk nystagmus. Optimumresponses occur when the rate of suc-cession of images is 3 to 12 per sec-ond. In a patient reporting unilateralblindness, the drum is rotated withboth eyes open. Once nystagmus iselicited, the unaffected eye is quicklycovered and the blind eye is observedfor continued nystagmus (Figure 7-2).

Although difficult, it is possible to sup-press optokinetic nystagmus especiallyif objects on the drum or tape are suf-ficiently large and the patient can avoidfixating on them (by looking over orbeyond the targets). Children, however,are generally unaware of these strategies.

The mirror test is based on the

movement of the eyes in response tothe image on a mirror as it is rockedback and forth. Patients cannot easilysuppress these eye movements. The

mirror must be large enough (approxi-mately 35 cm 67 cm) to prevent thepatient from looking around it. If the

patient states that he or she seesnothing in the mirror, but the pa-tients eyes move in response to themoving image as it is rocked back andforth, a subjectiveobjective mismatchhas been documented (Kramer et al,1979).

In addition, careful observation ofthe way the patient ambulates into andout of the examination area, avoiding

various obstacles (eg, furniture, otherindividuals), and assessment of his/her

affect (fear, indifference, or anger) mayalso provide valuable clues as to the

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TABLE 7-1 Continued

Fogging techniques

Bottom-up acuity

" Some Organic DisordersFrequently Misdiagnosedas Functional

Occult maculopathy

Paraneoplastic-associatedretinopathies/optic

neuropathy

Retinitis pigmentosa sinepigmento

Cone-rod dystrophy

Stargardt disease

Big blind spot syndromes

Bilateral occipital lobe infarcts

Creutzfeldt-Jakob disease

KEY POINTS

A Truly blind

persons can

easily touch

their fingertipstogether,

because this

requires only

proprioception,

not vision.

Patients with

functional

monocular

blindness may

touch their

fingertips

together when

viewing with

the normal

eye, but not

with this eye

occluded.

A With symptoms

of bilateral

blindness, the

absence of a

relative afferent

pupillary defect

does not imply

nonorganicvisual loss, as

the patient may

have bilateral

symmetric

anterior visual

pathway

pathology or

bilateral

posterior visual

pathway

disease.

FIGURE 7-1 Finger-touching technique.The patient is asked totouch the tips of the index

finger of each hand together. A, A blindperson can easily perform this task.B, Apatient with nonorganic visual loss whoclaims inability to touch her fingers together.

Reprinted with permission from Parrish RK II,editor. The University of Miami Bascom Palmer EyeInstitute atlas of ophthalmology. 2nd ed.Philadelphia: Butterworth-Heinemann, 2000.Copyright # 2000, Elsevier.




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nonorganic basis of the visual symp-toms. The surprise or shock techniqueentails showing objectionable photo-

graphs to the patient with the examinerobserving for an emotional response,such as smiling or gasping. This tech-nique is generally too confrontationalto recommend.

With symptoms of bilateral blind-ness, the absence of a relative afferentpupillary defect (RAPD) does not implynonorganic visual loss, as the patientmay have bilateral symmetric anterior

visual pathway pathology or bilateralposterior visual pathway disease.

Monocular complete visual loss.The swinging flashlight test provides

valuable objective evidence of monocu-lar prechiasmal (retina or optic nerve)damage. An RAPD may be present if a

patient has a monocular optic neurop-athy or an extensive retinal disorder.The absence of an RAPD in a patientreporting monocular blindness doesnot confirm a nonorganic disorder butgreatly increases suspicion of one. Pa-tients with true monocular blindness

and bilateral optic nerve dysfunctionmay not have an RAPD. Also, the pa-tient may state, My right eye is blind,

and have no RAPD, when in realitythe patient is erroneously lateralizing aright homonymous hemianopia to theright eye because of the fact that thefield loss of the right temporal hemi-field is larger than that of the left nasalhemifield.

Measurement ofstereoacuityis veryuseful in detecting monocular func-tional visual loss because stereopsis re-quires excellent binocular vision. Theuse of polarizing lenses is necessary

for the test (Levy and Glick, 1974).Two clinical techniques include theTitmus and the random-dot tests. TheTitmus test is a three-dimensional Polar-oid vectograph in a book format. Polar-oid glasses give the three-dimensionaleffect to the images in the book. Therandom-dot test consists of severalplates, each containing various shapes

constructed with colored dots. Someof the images are only apparent when

red-green glasses are worn. Most re-cently, the Mentor Binocular VisualAcuity Test, a computer-based test toevaluate stereoacuity, has been used.The finger-touching technique, opto-

kinetic nystagmus, and the mirror testare also useful.

Monocular reduced visual acuity.Using the following testing techniques,the examiner may be able to improveupon the patients stated acuity and

yet fail to establish 20/20 acuity in the

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FIGURE 7-2 Optokinetic nystagmus testing. A, In a

patient with nonorganic visual loss thedrum is first rotated with both eyes openand once optokinetic nystagmus is elicited, the unaffected eyeis quickly covered (B) and the blind eye is observed forcontinued nystagmus.

Reprinted with permission from Parrish RK II, editor. The University ofMiami Bascom Palmer Eye Institute atlas of ophthalmology. 2nd ed.Philadelphia: Butterworth-Heinemann, 2000. Copyright # 2000, Elsevier.





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affected eye. Although this objectivesubjective mismatch confirms a func-tional component to the visual loss, the

examiner is still not off the hook or aconcomitant organic component to thevisual loss may be present. Stereoacuityas mentioned above is also useful.

By convention, the prism shift test(as demonstrated byCase 7-1) uses a4-diopter (D) base-out prism and re-lies on normal refixation movements

to avoid diplopia. This technique ishelpful if the patient claims severelydiminished acuity (less than 20/400)

but less valuable in patients with onlyminimally reduced acuity (Figure 7-3).The prism dissociation test uses a

5-D or 6-D base-down prism (somepatients have fusional amplitudes upto 4-D) placed in front of the normaleye and a 0.5-D prism placed in anydirection over the impaired eye (so

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KEY POINT

A A variation of the

prism dissociation

test uses an 8-D

base-down prismplaced in front of

the normal eye and

no prism in front of

the impaired eye. A

vertical refixational

movement of the

eyes is observed

when the patient

shifts fixation from

the lower to the

higher image. To

prove normal

acuity, the patient

must read both

(doubled) 20/20

lines. A report of

diplopia also

provides evidence

Case 7-1

A 17-year-old adolescent presented with visual loss in the left eye (OS)noted 2 days earlier. She had developed a headache after the visual loss,and her vision had not yet improved. She indicated that she was blind inher left eye. She had no significant past medical history or allergies. Shedid not smoke cigarettes or consume alcohol.

On neuro-ophthalmic examination the patients blood pressure was119/62 mm Hg, and her heart rate was 68 beats/min. Visual acuity withoutcorrection was 20/20 in the right eye (OD) and no light perception OS.With prism dissociation using an 8-D base-down prism over the good eye(right eye), the patient read 20/20 in both eyes. Color vision was 9.5/10Ishihara plates OD, 0/10 Ishihara plates OS. Confrontational visual fieldswere full OD, and automated perimetry was full OD. Pupils measured6 mm in each eye (OU), with normal reactivity OU and no RAPD. Saccadic

and pursuit movements were normal in the vertical and horizontalplane. With an 8-D base-in prism, a shift occurred with alternate covertesting at distance. Ductions were full. Eyelids measured 8 mm OU.Exophthalmometry revealed Hertel readings of 18 mm OU, with a baseof 101 (normal). Trigeminal and facial nerves were intact. Intraocularpressures were 14 mm Hg OU (normal is 10 mm Hg to 21 mm Hg). Theeyelids, conjunctiva, cornea, and anterior chamber appeared normal OU.The optic nerves had cup-disc ratios of 0.2 OU (normal). The retinal vesselsand periphery appeared normal OU.

Comment.This patient has monocular visual dysfunction that is functionalor nonorganic in nature. The prism dissociation test is valuable when thepatient feigns visual loss in only one eye. With prism dissociation, the patient

saw 20/20 OU, indicating the patient can see normally with the blindleft eye. It is important that the patient can indeed see the 20/20 line in theblind eye. Anything less than 20/20 may indicate better acuity than whatwas claimed but not necessarily normal vision in the impaired eye. Thepupillary examination did not reveal an RAPD; this would be unusual ifthe patient did indeed have an optic neuropathy or pan-retinopathy in theblind left eye. With an 8-D base-in prism, a shift occurred with alternatecover testing at distance, indicating the patient can indeed fixate with theblind left eye. The patient and family should be counseled, indicatingthat the patients visual pathways are anatomically intact and that stresscan produce the patients symptoms. The family should be reassured thatthe patients vision should improve.




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the patient will not become suspicious).A 20/20 Snellen letter is projected andthe patient is asked if he or she can see

two vertically placed letters. If the pa-tient can read both letters, the acuityin the impaired eye is 20/20.

A variation of this test uses an 8-Dbase-down prism placed in front of thenormal eye and no prism in front ofthe impaired eye. The patient is askedif he or she can see the top and bot-tom lines and then asked to read eachline. A vertical refixational movementof the eyes is observed when the pa-tient shifts fixation from the lower to

the higher image. The higher imagerepresents visual acuity in the eye withthe prism (normal eye), and the lowerimage represents visual acuity in theimpaired eye. To prove normal acuity,however, the patient must read both(doubled) 20/20 lines. A report of dip-lopia also provides evidence of binocu-lar visual function (Slavin, 1990).

The polarizing lens testuses polar-ized glasses when viewing a Project-O-Chart, which projects letters seenalternately (Figure 7-4); one letter isseen by both eyes, the next by theright eye, the next by the left eye, andso on. A variation of this test includes apolarizer placed on an occluder with-out the patient wearing polarizing lenses.In this way, the examiner controls whicheye is examined, and it becomes moredifficult for patients to alternately closeone eye to determine what should beseen. The goal of the polarizing lens test

is to have the patient believe he or sheis reading with either the right or lefteye only.

During theduochrome test, patientsthink they are reading binocularly, butthey are actually reading with only oneeye. A red and green slide is super-imposed on the normal Snellen chart.

With this technique, the eye behind thered lens sees letters on both sides ofthe chart; the eye behind the greenlens sees only letters on the green side

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FIGURE 7-3 Prism shift test.A, A base-out prism in front of thenormal eye produces a shift of both eyes away fromthe prism base, followed by a fusional refixation

movement of the fellow eye (B).C, When the prism is placed overthe normal eye of a patient whose other eye is blind or poorly sighted,only the first binocular shift occurs, without a compensatory refixationmovement of the opposite eye.D, A truly blind eye does not refixate,and a prism placed before this eye should result in no movement ofeither eye.

f = fovea; OS = left eye.

Reprinted with permission from Parrish RK II, editor. The University of MiamiBascom Palmer Eye Institute atlas of ophthalmology. 2nd ed. Philadelphia:Butterworth-Heinemann, 2000. Copyright# 2000, Elsevier.





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of the chart. The lenses are arranged sothat the red lens is placed over the eye

with the purportedly decreased vision.

The patient is then asked to read thechart with both eyes open. If the pa-tient reads the entire line, the impairedeye must be functioning better than thepatient claims (Figure 7-5) (Ing et al,1995).

A variety of fogging techniquesmay be used for functional visual loss.The paired cylinder test uses trialframes with a +6-D and 6-D cylinderlenses placed at parallel (aligned) axesbefore the normal eye in the trial frame.

The patients refraction is placed beforethe impaired eye; if the patient doesnot require correction, equal powerplus and minus spheres can be used.

After the patient begins reading, a smallturn of the cylinder lenses makes theaxes no longer parallel and blurs thenormal eye so the patient is now read-ing with the impaired eye. The cylin-ders can be quickly moved so that theyare again aligned before the patient canrecognize what has occurred. On thesphere side, lens rotation will make nodifference in image quality (Figure 7-6).

Another method of fogging is to placea high-power (+6 D) spherical lensbefore the normal eye in a trial frameand the patients normal refractionbefore the impaired eye. The patient isasked to read large-print material, whichis gradually moved farther away. If thepatient is able to continue reading, theimpaired eye must be functioning be-

cause a high-power spherical lens willnot allow reading at distances greaterthan 25 cm with the normal eye. Astrong plus lens can also be used in thephoropter for fogging the normal eye.

Thebottom-up acuitymethod be-gins with acuity testing of the impairedeye on the smallest line on the Snellenchart (eg, 20/10). If the patient can-not see these letters, the examiner an-nounces the use of a larger line andthen uses the 20/15 line and several dif-

ferent 20/20 lines. The examiner contin-ually expresses surprise that such largeletters cannot be identified. If the pa-tient still denies being able to read theletters, he or she is asked to determinethe number of characters present and

whether they are round, square, etc.

Once the count is established, the ex-aminer might suggest that the charac-ters are letters and the first one is easierto identify than the others. This may taketime, and the examiner often has to wait

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FIGURE 7-4 American Optical (Buffalo, NY) polarizinglens test. A, The appearance of the entirechart viewed without a polarizing lens.

B, The appearance of the same chart when viewed throughone of the polarizing lenses. C, The appearance of the chartwhen viewed through the other polarizing lens. Note certainletters (V, C, K, N, S, R) can be seen through both lenses;others can be seen through one lens but not the other.

Reprinted with permission from Parrish RK II, editor. The University of MiamiBascom Palmer Eye Institute atlas of ophthalmology. 2nd ed. Philadelphia:Butterworth-Heinemann, 2000. Copyright # 2000, Elsevier.




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for the patients response. By the timethe very large letters (eg, 20/50) arereached, the patient often can be cajoledinto reading optotypes much smallerthan those read on initial acuity testing.The examiner may also have the patient

wear trial frames with multiple lenses

equaling the correct prescription andsuggest that these are special magnifyinglenses that might permit improved

vision.Distance and near discrepancies

compare visual acuity performance atdistance and near. In patients with

functional visual loss, the two measure-ments often are not consistent. Onecould also move the patient closer to

the Snellen chart and note if improvedacuity is present for the shorter dis-tance. It is important to correct for anyrefractive error, including presbyopia,and make certain no media distur-bances occur.

If a definite distance and neardiscrepancy exists and no refractiveerror occurs, this may be evidence forfunctional visual loss.

Electrophysiologic testing may beutilized to help diagnose nonorganic

visual loss. Pattern-reversal visual-evokedpotentials are widely available as anoninvasive measure of visual function.The test is usually performed monoc-ularly and waveforms generated at anamplitude and latency appearing atapproximately 100 ms (P100) after

visual stimulus. The patient must havevisual acuity sufficient to fixate on thecenter target of the computer screenfor the test to be reliable. An abnormal

visual-evoked potential does not nec-essarily guarantee organic visual loss.Patients may alter the waveforms voli-tionally by using a variety of maneu-

vers, such as meditation, daydreaming,convergence, defocusing, or other

tricks. It is a useful test if completelynormal (Morgan et al, 1985).A full-field electroretinogram (ERG) is

a useful test to eliminate occult retinaldystrophies (retinal dystrophy withoutfindings on funduscopic examination).Testing reliability does not depend on

visual fixation so the patient may havevery poor vision and still yield a re-liable test. Multifocal ERG is a relativelynew technique that represents a signifi-cant advance over conventional full-field

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FIGURE 7-5 Duochrome test. A, Appearance of chart with superimposed red-greenduochrome slide when viewed without the red-green lenses. With thistechnique, the eye behind the red lens sees letters on both sides of the chart

(B), and the eye behind the green lens sees only letters on the green side of the chart (C).

The lenses are arranged so that the red lens is placed over the eye with the decreased vision,and the patient is then asked to read the chart with both eyes open. If the patient reads theentire line, the abnormal eye must be functioning better than the patient claims.

Reprinted with permission from Parrish RK II, editor. The University of Miami Bascom Palmer Eye Institute atlas ofophthalmology. 2nd ed. Philadelphia: Butterworth-Heinemann, 2000. Copyright # 2000, Elsevier.

KEY POINT

A A normal

full-field and

multifocal

electroretinogramand a normal

pattern visual-

evoked potential

in a patient who

presents with

severe (but

good enough

to fixate)

monocular or

binocular visual

loss and an

otherwise

normal clinical

examination

supports the

suspicion of a

nonorganic

disturbance of

vision. This is

assuming that

neuroimaging

(contrasted

cranial and

orbital MRI)

has beenperformed.





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electroretinography in the evaluationof macular disease (Sutter and Tran,1992). Conventional ERG measures the

summed electrical activity of the entireretina and thus is relatively insensitive tolocalized retinal defect. For example, it ispossible to have a completely normalconventional ERG in an eye with visionof hand motion or worse. This occursbecause the fovea, which accounts foracuity, contributes less than 5% ofthe total electrical response elicited byconventional ERG. Multifocal ERG, incontrast, measures summed responsesfrom small defined segments of the

posterior pole centered around thefovea, typically 103 separate responsesfrom each area. Thus, localized retinaldefects are readily detected by this test,and multifocal ERG responses correlate

well with visual acuity in outer retinaldisease (Hood, 2000).

A normal full-field and multifocal ERGand a normal-pattern visual-evoked po-tential in a patient who presents withsevere (but good enough to fixate) mon-ocular or binocular visual loss andan otherwise normal clinical examina-tion support the suspicion of a non-organic disturbance of vision. This isassuming that neuroimaging (cranialand orbital MRI with contrast) has beenperformed.

Binocular reduced visual acuity.Testing methods that are helpful in-clude bottom-up acuity, distance andnear discrepancies, the use of specialcharts, and the doctor killing refrac-

tion. Also, stereoacuity testing, prismshift and prism dissociation tests, po-larizing lenses and duochrome tests,and fogging techniques may be useful.

Monocular diplopia. Monoculardiplopia does not remit when coveringone eye and is most commonly pro-duced on the basis of high astigmatismeither due to corneal or lens change.Monocular diplopia may also resultfrom a corneal scar, cataract, vitreousopacity, or macular disease. Very rarely

it results from a neuro-ophthalmic cause(eg, tumor or hemorrhage of the oc-cipital cortex or lesions of the frontal

eye fields). When diplopia has a corticalorigin, it is present in both eyes (bi-lateral monocular diplopia) and the dip-lopia is identical in each eye. Cerebralpolyopia is the duplication of the vi-sual image in space with monocular

viewing. Two images or dozens maybe present. All images are seen withequal clarity; there is no resolution

with a pinhole as occurs with refractivecauses, and the image is unchangedif viewed monocularly or binocularly.

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FIGURE 7-6 Fogging technique: Paired cylinders. A , Trialframes with +6-D and 6-D cylinder lensesare placed at parallel axes before the normal

eye in the trial frame. After the patient begins reading, asmall turn of the cylinder axes makes the axes no longerparallel (B) and blurs the normal eye so the patient is nowreading with the impaired eye.

Reprinted with permission from Parrish RK II, editor. The University of MiamiBascom Palmer Eye Institute atlas of ophthalmology. 2nd ed. Philadelphia:Butterworth-Heinemann, 2000. Copyright # 2000, Elsevier.




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It is an extremely rare syndrome andtypically associated with a homony-mous visual field defect. In general, if

bilateral monocular diplopia does notremit with pinhole, cranial neuroimag-ing is required to evaluate for hemi-

spheric lesions. Once all is ruled out,the clinician should suspect a functionalcause for the monocular diplopia.

Visual field abnormalities. Themost common functional visual fieldabnormality is generalized constriction.The tangent screen is useful in thesecases. The patient is initially tested witha stimulus at 1 m. When the patient istested at 2 m, the stimulus size is alsodoubled so the size of the test object inrelation to the distance of the patient

from the screen remains constant. In anormal patient, the visual field shouldexpand (funnel vision) and not stay thesame or get smaller (tunnel vision), asoften occurs in patients with functional

visual loss (Kline, 2000).If kinetic Goldmann perimetry is

used, patients with functional visualloss often give inconsistent responses,

with spiraling (Figure 7-7A) or over-lapping of isopters (Figure 7-7B). Spi-raling of isopters indicates that thepatient is responding to a constantstimulus but at variable positions, usu-ally responding closer to fixation eachtime the stimulus is presented. Over-lapping isopters are not physiologic,because the patients initial response tostimuli occurs closer to fixation thanthat of a smaller or less bright stimulus(opposite what it should be). In afunctional monocular temporal defect,the binocular visual field (tested with

both eyes open) may also have a tem-poral defect that respects the verticalmeridian (Figure 7-7C). The patient

with a true monocular hemianopia dem-onstrates only loss of the temporalcrescent on binocular visual field test-ing because of overlap of the intact na-sal field from the opposite eye (Keane,1979).

A patient with true monocular blind-ness should demonstrate the absenceof a temporal crescent on the side of

116

FIGURE 7-7 Many monocular and binocular visual fieldabnormalities may be detected with Goldmannperimetry in a patient with nonorganic visual loss.

Examples of visual field abnormalities include spiraling isopters (A) andcrossing isopters (B). C, Nonorganic monocular hemianopia with atemporal defect on binocular field testing. D, E, A patient with truemonocular full-field blindness should demonstrate the absence of thetemporal crescent on binocular visual field testing versus a nonorganicnormal binocular field.

Reprinted with permission from Parrish RK II, editor. The University of Miami BascomPalmer Eye Institute atlas of ophthalmology. 2nd ed. Philadelphia: Butterworth-Heinemann, 2000. Copyright # Elsevier, 2000.





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the visual loss with binocular field test-ing, while a patient with functionalhemianopia may demonstrate a nor-

mal binocular field (Figures 7-7Dand 7-7E).Automated perimetry often confuses,

rather than clarifies, the clinical picturein patients with functional visual fieldloss. Although abnormalities in the re-liability indices in these patients mayoccur, testing does not always ade-quately reflect fixation, false-positive,or false-negative errors. For example,in patients with feigned visual field de-pression (eg, no positive responses),

the false-negative rate may not behigh because the patient responds nega-tively to all stimuli, producing no false-negative responses. Clinicians must beaware of this potential pitfall and em-ploy manual methods of visual fieldtesting to corroborate abnormalitiesdetected with automated techniques(Stewart, 1995).

Patients with functional field lossmay demonstrate deficits that respectthe horizontal and/or vertical meridians,thus mimicking a disorder of the an-terior or posterior visual pathways. Onoccasion, it may be difficult to differen-tiate nonorganic from organic visualfield loss, and patients will require fur-ther evaluation.

Functional Disorders Affectingthe Efferent Visual Pathway

Voluntary nystagmusis characterized byirregular brief bursts of rapid frequency,

low-amplitude eye movements. Mostcommonly they are horizontal, althoughon occasion they may be vertical or tor-sional. The eye movements are bilateraland conjugate and are often associated

with convergence, fluttering eyelids,blinking, or strained facial expression.

Voluntary nystagmus is difficult to main-tain for longer than 10 to 12 seconds. Itis actually back-to-back saccades withoutan intersaccadic interval. Patients oftenreport oscillopsia and reduced vision.

These individuals are identified by thevolitional appearance of the ocular move-ment disorder, absence of nystagmus

when they are distracted, inability to sus-tain the fast eye movements, and the lackof other neuro-ophthalmic abnormali-ties. Voluntary nystagmus can be diag-nosed using eye movement recordings.

Patients with functional ocular mo-tility disorders may report an inabil-ity to move their eyes horizontally or

vertically. Such gaze palsies may beovercome by a variety of maneuvers,including oculocephalic testing (dollshead maneuver), optokinetic testing,

mirror tracking, and caloric testing.Spasm of the near reflex, a syn-

drome characterized by episodes ofintermittent convergence, increasedaccommodation, and miosis, is usuallyobserved in patients with functional

visual loss but has been associatedwith Chiari I malformation, posteriorfossa tumors, pituitary tumors, and

head trauma (Dagi et al, 1987). Pa-tients generally report diplopia and, attimes, micropsia. Since the degree ofconvergence is variable, some patientsdemonstrate marked convergence ofboth eyes, resulting in a large esotro-pia. Others show a lesser degree of

convergence in which one eye remainsrelatively straight while the other con-

verges. Typically, the spasm cannotbe maintained and the esotropia re-solves with monocular testing. Spasmof the near reflex may be mistaken forunilateral or bilateral abducens nerve

palsies,divergence insufficiency,horizon-tal gaze paresis, or ocular myasthe-nia. In addition, patients may reportblurred distance vision from up to 8 Dto 10 D of induced myopia. Refraction

without and with cycloplegia duringthe period of spasm (dynamic retinos-copy) establishes the presence of theinduced myopia. The variability ofconvergent eye movements, lack of

other neuro-ophthalmic abnormalities,resolution with monocular testing, and

117

KEY POINT

A If kinetic Goldmann

perimetry is used,

patients with

functional visualfield defects

often give

inconsistent

responses, with

spiraling or

overlapping of

isopters. Spiraling

of isopters

indicates that

the patient is

responding to a

constant stimulus

but at variable

positions, usually

responding closer

to fixation each

time the stimulus

is presented.




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occurrence of miosis with associatedesotropia permit the correct diagnosis.

Functional Disease ProducingPupillary Abnormalities

Few patients provoke more anxiety forthe physician than those with head-ache and a dilated fixed pupil. Thedifferential diagnosis can be narrowedto four basic processes: (1) pharma-cologic blockade, (2) trauma (with or

without pupillary sphincter tears) and

inflammation, (3) oculomotor nervepalsy, and (4) Adie tonic pupil. Evi-dence of trauma and inflammation maybe sought at the slit lamp looking forsphincter damage and pigmentation.Pharmacologic blockade may occurbecause of inadvertent or purposeful

application of mydriatic eye drops orfrom the use of a scopolamine patchto prevent motion sickness or postop-erative nausea. The pilocarpine testreadily distinguishes parasympatheticdenervation from pharmacologic block-ade. In the latter, 1% pilocarpine can-

not overcome the receptor blockage,and the pupil remains large. A fixeddilated pupil from injury to the thirdcranial nerve will constrict in responseto 1% pilocarpine. Adie tonic pupil willconstrict to 0.1% pilocarpine since de-nervation supersensitivity will be pres-ent. Widely dilated pupils may be seenin young patients, likely due to in-creased levels of circulating catechol-amines. Rarely, patients are able to

voluntarily dilate both pupils.

Intermittent miosis will occur due tospasm of the near reflex, accompaniedby changes in eye position (esotropia)and accommodation. Miosis may alsobe produced pharmacologically with

pilocarpine.

Functional Disease AffectingEyelid Position and Function

Voluntary blepharospasmmay be uni-lateral or bilateral. At times, it may cause

nonorganic ptosis. Most cases of nonor-ganic blepharospasm occur in childrenor young people and may be triggered

by a particularly emotionally traumaticevent. The blepharospasm may respondto psychotherapy, hypnosis, behaviortherapy, and biofeedback or may spon-taneously resolve on its own.

PATIENT MANAGEMENT

In general, patients with symptoms offunctional visual disorders are bestmanaged with an understanding ap-proach and words of encouragement.

It is prudent to allow patients a wayout by reassuring them that although

their disorder does not suggest un-derlying damage to the CNS, they do,in fact, have a problem that is expectedto resolve over time. Often with one ortwo follow-up visits the symptoms willclear, and they can be reassured of anexcellent prognosis.

In patients with both organic andfunctional symptoms, it is best to ad-dress the former problem and attemptto downplay the latter. With appropri-ate management of the organic visualdisturbance, the patients anxiety maybe alleviated and the nonorganic symp-

toms resolve.Despite a thorough examination and

discussion, more than half of patientswith functional visual loss continue tomanifest symptoms on follow-up exami-nations. In addition, functional patients

with associated psychiatric disorders

are less likely to recover. If a func-tional disorder is proven, patients aretold that there is no anatomic causefor their visual dysfunction and thatsometimes stress can be a contributorto their problem. It is suggested thatit may be beneficial to have a psychiat-ric evaluation to help better managethe stress. The notes should indicatethat there is a nonorganic component,

and the words malingeringorhysteri-calshould never be used. Also, never

118

KEY POINTS

A The pilocarpine

test readily

distinguishes

parasympatheticdenervation

from

pharmacologic

blockade. In

the latter, 1%

pilocarpine

cannot

overcome

the receptor

blockage, and

the pupil

remains large.

A It is prudent to

allow patients a

way out by

reassuring

them that

although their

disorder does

not suggest

underlying

damage to the

CNS, they do,

in fact, have

a problem thatis expected

to resolve

over time.





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label a patient as having functionaloverlay unless normal visual functioncan be proven.

Finally, it is always prudent to fol-low a patient with what appears to beonly a functional visual disturbancebecause organic and functional dis-eases often coexist (Scott and Egan,2003). The diagnosis of a functional

syndrome is one of exclusion and, ide-ally, of retrospection.

ACKNOWLEDGMENTS

This work was supported in part byan unrestricted grant from the Re-search to Prevent Blindness, Inc., New

York, NY.

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