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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.
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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
108
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
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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
110
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.
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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
112
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
113
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.
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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.
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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.
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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.
REFERENCES
Brodsky MC, Baker RS, Hamed LM. Transient, unexplained, and psychogenic visual loss
in children. In: Brodsky MC, Baker RS, Hamed LM, eds. Pediatric neuro-ophthalmology.New York: Springer-Verlag New York, Inc., 1996:187193.
Clarke WN, Noel LP, Bariciak M. Functional visual loss in children: a common problemwith an easy solution. Can J Ophthalmol 1996;31(6):311313.
Dagi LR, Chrousos GA, Cogan DC. Spasm of the near reflex associated with organicdisease. Am J Ophthalmol 1987;103(4):582585.
Hood DC. Assessing retinal function with the multifocal technique. Prog Retin Eye Res2000;19(5):607646.
Ing EB, Younge BR, Leavitt JA, Fitzpatrick PJ. Functional visual loss and the duochrometest. Can J Ophthalmol 1995;30(1):3536.
Kathol RG, Cox TA, Corbett JJ, et al. Functional visual loss: II. Psychiatric aspects in 42patients followed for 4 years. Psychol Med 1983;13(2):315324.
Keane JR. Hysterical hemianopia: the missing half field defect. ArchOphthalmol 1979;97(5):865866.
Keltner JL, May WN, Johnson CA, Post RB. The California syndrome: functional visualcomplaints with potential economic impact. Ophthalmology 1985;92(3):427435.
Kline LB. Techniques for diagnosing functional visual loss. In: Parrish, RK II, editor. TheUniversity of Miami Bascom Palmer Eye Institute atlas of ophthalmology. 2nd ed.Philadelphia: Butterworth-Heinemann, 2000:493501.
Kramer KK, La Piana FG, Appleton B. Ocular malingering and hysteria: diagnosis andmanagement. Surv Ophthalmol 1979;24(2):8996.
Levy NS, Glick EB. Stereoscopic perception and Snellen visual acuity. Am J Ophthalmol1974;78(4):722724.
Miller NR. Neuro-ophthalmologic manifestations of nonorganic disease. In: Miller NR,Newman NJ editors. Walsh & Hoyts clinical neuro-ophthalmology. 6th ed. Philadelphia:Lippincott Williams & Wilkins, 2005:13151334.
119
Continuum Lifelong Learning Neurol 2009;15(4)
Copyright @ American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
7/24/2019 Functional Neuro Ophthalmic Conditions.9
15/15
Morgan RK, Nugent B, Harrison JM, OConnor PS. Voluntary alteration of pattern visualevoked responses. Ophthalmology 1985;92(10):13561363.
Scott JA, Egan RA. Prevalence of organic neuro-ophthalmologic disease in patients with
functional visual loss. Am J Ophthalmol 2003;135(5):670675.
Slavin ML. The prism dissociation test in detecting unilateral functional visual loss.J Clin Neuroophthalmol 1990;10(2):127130.
Stewart JF. Automated perimetry and malingerers: can the Humphrey be outwitted?Ophthalmology 1995;102(1):2732.
Sutter EE, Tran D. The field topography of ERG components in man-1: the photopicluminance response. Vision Res 1992;32(3):433446.
Thompson HS. Functional visual loss. Am J Ophthalmol 1985;100(1):209213.
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