Journal of Clinical Neuroscience 14 (2007) 1–7 www.elsevier.com/locate/jocn
Review
Practical clinical approaches to functional visual loss Celia S. Chen a
a,*
, Andrew W. Lee b, Arthur Karagiannis a, John L. Crompton a, Dinesh Selva a
Department of Ophthalmology & Visual Sciences, University of Adelaide, North Terrace, Adelaide, South Australia, Australia b Department of Neurology, The Queen Elizabeth Hospital, Woodville Road, Woodville, South Australia, Australia Received 14 November 2005; accepted 14 March 2006
Abstract Functional visual loss (FVL) refers to subnormal vision or altered visual fields where no underlying pathology of the visual system can be found. It may be seen in a continuum from frank malingering to hysteria. FVL may first present to the general practitioner or physician and the financial burden of evaluation and potential disability-related claims may be substantial. Diagnosis relies on a high index of suspicion and demonstration with a few simple tests that the patient has better vision than alleged. The aim of this review is to provide a practical approach to examination of patients with suspected functional visual loss. An accurate and early diagnosis of FVL starts with a high index of suspicion. Only a few of the tests need to be learned well, performed smoothly and confidently. These clinical tests obviate the need to perform expensive imaging such as magnetic resonance imaging and if used in the correct setting have the potential to reduce further the cost of diagnosis. Management requires an understanding approach and confrontation is seldom helpful. It is important to stress to the patient that FVL has a good prognosis, thereby providing ‘‘a way out’’ and giving the patient the opportunity to recover. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Functional Visual Loss; Binocular; Monocular; Stereopsis
1. Introduction Functional visual loss (FVL) refers to subnormal vision or altered visual fields where no underlying pathology of the visual system can be found.1,2 It is a clinical diagnosis which is made when the physician demonstrates that visual acuity is better than subjectively alleged. Functional visual loss may be seen in a continuum of clinical settings, from frank malingering3–5 with the aim of secondary gain, to a factitious disorder which is symptom-focused or is hysteria-based6–9 with subconscious expression of visual symptoms. FVL may be seen in any age group10 but is seen in 1–5% of referrals to ophthalmologists.11,12 The total incidence may be greater, given that patients may also present to their general prac-
*
Corresponding author. Tel.: +61 8 8222 5222; fax: +61 8 8222 5221. E-mail address:
[email protected] (C.S. Chen).
0967-5868/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jocn.2006.03.002
titioners, internal medicine physicians, psychiatrists or neurologists.13 The financial impact of FVL is estimated at an average of greater than US$500 per patient spent on diagnosis and a potential of millions of dollars in claims for disability benefits, workers’ compensations or insurance claims.14 A thorough ophthalmological and neuro-ophthalmological examination should be undertaken prior to entertaining a diagnosis of functional visual loss and a high level of suspicion is important for early diagnosis of FVL to avoid unnecessary investigations and false claims. The aim of this review is to provide a practical approach to examine patients with suspected FVL. The condition may be considered in isolation in terms of the visual afferent and efferent pathway;15–17 however, more commonly, the clinician is faced with a variety of symptoms including binocular visual loss, monocular visual loss or monocular decrease in vision. The approach to each of these three categories is discussed.
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2. Assessment of total binocular blindness The aim of the examination is to demonstrate that the patient is actually ‘‘seeing’’. These tests can be performed in a primary care clinical setting without sophisticated instrumentations. The clinician needs to be able to understand the basis of some of these and perform them in a smooth and professional manner. Best results are often produced without confrontation. FVL is not a diagnosis of exclusion but rather the confirmation that the patient has better vision than alleged; hence, the more tests performed showing inconsistencies of symptoms and signs, the more reliable is the diagnosis of FVL. The examination starts from the moment the patient walks into the consulting room and much information can be gained by careful observation. A truly blind patient will move cautiously and bump into objects naturally. A functionally blind patient will deliberately bump into objects or exaggerate movements. Observe hand-shaking. Furthermore, observe the accompanying person and their behaviour toward the patient. It provides a very strong clue to the ‘‘overall picture’’. There are non-visual tasks which utilize proprioception.17,18 The fingertip touching test is performed by asking the patient to bring their index fingers together. A truly blind patient can easily touch the tips of the fingers together. Those who are functionally blind tend not to (Fig. 1). Similarly, the signature test is also a non-visual task. A patient with organic visual loss can easily sign his/her name without difficulty, but a FVL patient may produce a bizarre signature. Tests may also utilize neurological reflexes which are difficult to suppress. For instance, the miosis, convergence and accommodation reflex which originates from the pretectal nuclei help form the basis of the mirror test. Sudden unannounced production of a mirror in front of the patient is a strong stimuli for the patient to look at self and induce accommodation, as well as convergence, and objectively, miosis. The optokinetic reflex relies on the higher cortical function of smooth pursuit to track an object followed by quick corrective saccades to re-fixate. To stimulate this reflex, a striped neck tie, a broad piece of black and white
striped material, or if available, a rotating optokinetic drum, can be moved slowly in front of the patient and observe the eye movement. If the eye moves with the drum/ tie, this suggest either a bilateral occipital cortical blindness or the patient is seeing and a functional component has been established.15 Lastly, the pupil reflex is the only objective way to assess the afferent visual pathway. The pupillary reaction relies on the afferent pathway from the retina to optic nerve, crossing over at the optic chiasm to the optic tract which contains bilateral afferent fibers, deviating from the lateral geniculate nucleus to the pretectal nuclei in the midbrain. Cross-over occurs at the midbrain before the efferent pathway, starting from the Edinger-Westphal nuclei to the ciliary ganglion to the iris sphincter muscle. A normal pupillary response in a patient who claims bilateral visual loss suggests bilateral symmetrical visual pathway pathology, such that afferent input is reduced bilaterally, or the patient is cerebrally blind such as from bilateral occipital disease, or there is a functional cause for visual loss.15,18 Tests utilizing shock value are designed to elicit surprise in response to a visual cue. For instance, the menace reflex is when the examiner presents visual threats such as closed fist to the eye and observes for blinking or flinching. The tearing reflex is the production of sudden strong illumination in front of the patient which can produce tearing. The examiners can also be innovative and dramatic such as suddenly dropping an object and observe if the patient reaches out to salvage it. As a parting gesture, hold out your hand while bidding the patient goodbye which also serves as a distraction, and observe if the patient shakes your hand in response. 3. Assessment of monocular blindness This is more common than binocular visual loss and the aim of assessment is to demonstrate that the ‘‘blind’’ eye is seeing, using ocular viewing confusion or tests that require binocularity. The relative afferent pupillary defect (RAPD) provides objective evidence of the anterior visual pathway. Monocular visual loss in the absence of RAPD raises suspicion of
Fig. 1. (a) A truly blind person can easily touch the tips of the fingers together using proprioception, (b) those with FVL tend to exaggerate inability to do so.
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FVL. Furthermore, it is important to consider if all the clinical signs correlate with each other. The absence of an RAPD in a monocular visual loss, in the absence of optic nerve pallor or corresponding visual field change, does not correlate with monocular blindness. The fogging test utilizes ocular confusion to fog or to blurring the ‘‘good eye’’ without the patient’s awareness, hence the patient is tricked into reading out of the allegedly ‘‘bad eye’’. Start with a +4 diopter cylinder and –4 diopter cylinder aligned on the same axis in both eyes, which neutralize each other, producing a lens with no refractive power. Encourage the patient to read down the chart and slowly rotate one of the cylinders in the ‘‘good’’ eye to 90° of the other cylinder. This blurs the good eye and the patient may be tricked into reading out of the ‘‘blind’’ eye, demonstrating a vision that is better than alleged
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(Fig. 2). Talking to the patient during the test helps to distract him/her from the intended purpose. If the patient is observed to check what is going on by closing each eye in turn, then suspect FVL. The tests that require binocularity will help demonstrate that the ‘‘bad eye’’ is actually seeing. The stereoscopic test is such that binocularity is required to see objects in three dimensions. Using the Titmus stereo test or the TNO test, which are portable booklets with stereoptic images, the stereopsis can be converted to visual acuity (Fig. 3 and Table 1).19 Polaroid glasses and vectographic slide tests employ the same principle, whereby polaroid glasses are used to dissociate one eye from the other, such that each eye sees a different portion of an eye chart. If the patient reads the entire line, he/she is using both eyes and functional visual loss is established.
Fig. 2. (a) Slowly turning the cylinders at 90° to each other blurs the ‘‘good eye’’ and (b) the patient is tricked to read out of the ‘‘bad eye’’ where the axes are parallel, creating a clear lens.
Fig. 3. The titmus stereoscopic test relies on binocular vision and each corresponding symbol, e.g. the circles or animals, represent a specific stereoacuity in arc seconds.
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Table 1 The degree of stereopsis in arc seconds may be converted into visual acuity19 Stereopsis (arc second)
Visual acuity
40 52 60 78 94 124 160
20/20 20/30 20/40 20/50 20/70 20/100 20/200
The Prism Shift Test20 employs both the confusion and the binocularity principle. A 10 diopter base-out prism is placed in front of the affected/‘‘blind’’ eye. A patient with normal binocular vision will show a movement of both eyes towards the apex of the prism, followed by a shift of both eyes back towards the centre. Similarly, the diplopia test is
a sophisticated test whereby the ‘‘blind’’ eye is occluded while a strong prism is held with the apex bisecting the pupil of the ‘‘good’’ eye. The patient will admit to monocular diplopia. As the ‘‘blind’’ eye is uncovered, the entire prism is placed before the good eye. If the patient is only seeing out of the ‘‘good’’ eye, he/she will see a single displaced image but not diplopia. If the patient reports diplopia, they are seeing out of both eyes and functional visual loss is established (Fig. 4). In addition, all of the above-mentioned tests for ‘‘binocular blindness’’ can be used for ‘‘monocular blindness’’ by completely occluding the ‘‘good’’ eye. 4. Assessment of ‘‘reduced vision’’ Reduced vision may take the form of reduced visual acuity or reduced visual fields. In patients claiming FVL
Fig. 4. The diplopia test.20 (a) The ‘‘blind eye’’ is occluded and a strong prism is placed over the ‘‘good eye’’ to produce monocular diplopia. (b) The prism is then placed over the good eye. If only the good eye is seeing, it will see a single displaced image. (c) If both eyes are seeing, there will be two images, one from the displaced image of the ‘‘good eye’’, the second image from the alledged ‘‘blind eye’’. Hence if the patient admits to diplopia, he/she is seeing out of both eyes.
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of reduced acuity, the fogging test and the stereoacuity test are helpful to demonstrate that the visual acuity is better than claimed. In those with alleged reduced visual fields, test the visual field to confrontation standing at 1 m and 2 m in front of the patient. The visual angle is subtended in an arc such that the field at 2 m should be twice the size of that at 1 m (Fig. 5a). A patient with FVL will not be aware of this and feign a smaller field when further away. A more objective way is to use manual kinetic perimetry such as the Goldman visual field testing to map out the patient’s field. Characteristic fields include tunneling visual fields, spiraling isopters (Fig. 5b) or cross-over isopter (Fig. 5c).21–23 The binocular visual field versus the monocular field can also help demonstrate FVL. In those with alleged monocular decreased visual field, map out the field defect. Then map out the binocular visual field. Physiologically, the nasal visual field of the ‘‘good eye’’ extends 50° such that the
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patient should still have a wide visual field (Fig. 5d). Those with FVL tend to report the same visual defect with binocular viewing, thus demonstrating inconsistencies and a functional component. Furthermore, those with claimed monocular visual loss tend to have an absence of blind spot on kinetic testing or static perimetry, as the patient deliberately attempts non-fixation on the target. In patients feigning a tunnel vision defect or a homonymous visual field loss, use a red target on a wand with the pretext of testing eye movements. Once accomplished in the standard fashion eliciting pursuit and saccade, the target can be rapidly switched from the normal field to the alleged abnormal field ‘‘to test the fast movement of the eye’’, but in fact testing the peripheral visual fields as one moves the target rapidly and randomly in the periphery. The patient with FVL will refixate smoothly on the ‘‘fast movement test’’ demonstrating that they do in fact have full peripheral vision.
Fig. 5. (a) Visual field at 2 m (right) should be twice the size of that at 1 m (left). Patients with FVL may feign a smaller field when further way. (b) Spiralling isopter: during manual perimetry, patients with FVL may allege the visual field to be getting smaller especially with repeat testing at the same axis. (c) Cross-over isopter: using two different targets, e.g. different colour or size of targets, patients with FVL may report difference in field defect, hence crossing isopter. (d) A patient alleging monocular temporal hemianopia (left) should have only a temporal crescent (right) on binocular viewing. A patient with FVL tends to feign persistent hemianopia even with binocular viewing.
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5. Management Management should be directed toward stressing a good prognosis to encourage visual recovery and attempts to find the underlying cause for FVL. A careful history is required. The psychosocial setting is important to understand the background of the presentation. Lim et al.24 noted that concomitant psychosocial events were mainly social in children and related to trauma in adults. A child may adopt FVL as a ‘‘cry for help’’ if subject to bullying at school, underachieving or suffering from physical, psychological or sexual abuse. Sometimes a secondary gain is apparent such as mimicking a friend who has acquired spectacles; hence, an observation of a rush for spectacles after the release of the Harry Potter books. An adult may have suffered a trivial eye injury during an accident at work, but workplace issues/disputes can lead to exaggerated claims for damage. A careful examination is also required. Some rare ophthalmic conditions such as Stargardt’s disease, cone dystrophies or other hereditary retinal dystrophies, paraneoplastic syndrome such as cancer-associated retinopathy (CAR) or melanoma-associated retinopathy (MAR) may
have very subtle clinical signs. Diagnosis of these conditions may require further ophthalmic investigations such as fluorescein angiogram to show the pathognomonic dark choroid in Stargardt’s disease or multifocal electroretinogram (mfERG) showing the retinal pathologies in cone dystrophies, CAR and MAR.25 More frequently, patients with FVL may have co-existing ocular pathology and their concern about the latter may incite or exacerbate the functional component. It is important to correlate all the signs such as the RAPD, optic nerve function (visual acuity, colour visions, visual fields and subjective brightness) and appearances of the optic nerves. If inconsistencies exist, smooth performance of a few of the above tests demonstrating that the vision is better than alleged confirms the functional component, which must be addressed when treating the underlying ocular pathology. Once FVL is demonstrated, the discussion should be phrased in an understanding and supportive manner. Confrontations are rarely useful.26 A good prognosis should be emphasized, which helps to give patients ‘‘a way out’’. At least one follow-up appointment is recommended giving the patient the perception that their problem is undergoing active management and establishes rapport.
Table 2 Summary of clinical tests for functional visual loss Clinical tests Total binocular blindness Observation Finger-tip test Signature test Mirror test Optokinetic test Pupil response
Principle
Strength
Weakness
Clue to true or simulated difficulties in visual tasks Proprioceptive tasks and does not require vision Convergence, miosis and accommodation reflex Optokinetic reflex of smooth pursuit Detection of afferent and efferent pathway
Important in overall assessment
Subjective
Easy clinical test to perform and characteristic outcomes in FVL Difficult natural reflex to suppress Natural reflex, easy to reproduce
–
Menace reflex
Shock value
Tearing reflex
Tearing with bright light
Monocular blindness Pupil response
Direct afferent visual pathway light testing
Objective
Clear demonstration of patient seeing Difficult natural reflex to suppress Objective. RAPD correlates with optic pathway pathology anterior to LGN Diagnostic of functional component Can convert arc second to visual acuity
Result best produced with sudden introduction of a mirror Differential of bilateral occipital lobe cortical blindness Differential of symmetrical afferent pathology, bilateral occipital lobe lesions Care in patient selection Light intensity dependent and poor reproducibility Organic lesions posterior to LGN
Fogging test
Elicit better vision than claimed
Stereopsis testing
Require binocular vision
Prism shift test
Demonstrates binocular vision
Hard for patient to guess result
Patient may have poor stereoacuity due to other causes, e.g. developmental Operator dependent
Reduced visual acuity Fogging test and stereoacuity
As above
As above
As above
Reduced visual field Visual field to confrontation, kinetic and static perimetry
Physiological visual field characteristics
Characteristic patterns such as tunnelling, spiralling visual fields or absent blind spots
Kinetic perimetry require experienced technician
FVL = functional visual loss, RAPD = relative afferent pupillary defect, LGN = lateral geniculate nucleus.
Operator dependent
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Using the therapeutic approach described above, between 45% and 78% experience resolution of all visual symptoms.27–31 Good prognostic indicators include young age and absence of any associated psychiatric disease.27 Other non-specific treatments include non-medical eye drops, eye exercises, glasses or placebo medicine. Reassurance alone is significantly more likely to result in recovery than the addition of non-specific treatments.28 Although the visual prognosis is usually excellent, improvement may be slow and incomplete in a small proportion of patients. Adults are twice more likely than children to have co-existing psychiatric disease24 and these patients are more likely to have persistent FVL. Kathol et al.29 suggested that in these individuals the focus of treatment should be directed toward the psychiatric condition rather than the visual dysfunction. 6. Conclusion An accurate and early diagnosis of FVL starts with a high index of suspicion. The aim is to demonstrate better sight than claimed by the patient. A careful history is important to gain insight into possible underlying factors. Examination should be thorough to exclude organic causes and consider if all the signs correlate well. If inconsistencies occur and FVL is suspected, only a few of the above tests need to be learned well, performed smoothly and confidently to demonstrate better vision than alleged (Table 2). These clinical tests used in the correct setting obviate the need to perform exhaustive and expensive investigations such as magnetic resonance imaging and reduce the economic impact of false disability claims. Management requires an understanding approach to uncover possible underlying motives. Confrontation is seldom helpful. It is important to stress to the patient that FVL has a good prognosis, providing ‘‘a way out’’, giving the patient the opportunity to recover. References 1. American Academy of Ophthalmology. The patient with functional visual disorders. In: Liesegang TJ, Deutch TA, Grand MG, editors. Basic and Clinical Science Course: Section 5–Neuro-ophthalmology. Philadelphia, PA: J.B. Lippincott Co; 2002. p. 293–304. 2. Duke-Elder S. Ophthalmic Optics and Refraction. London: Henry Kimpton; 1970., pp. 490–499. 3. Kramer KK, LaPiana FG, Appleton B. Ocular malingering and hysteria: diagnosis and management. Surv Ophthalmol 1979;24:89–96. 4. Miller BW. A review of practical tests for ocular malingering and hysteria. Surv Ophthalmol 1973;17:241–6. 5. Mace CJ, Trimble MR. ‘Hysteria’, ‘functional’ or ‘psychogenic’? A survey of British neurologists’ preferences. J R Soc Med 1991;84:471–5. 6. Hafeiz HB. Hysterical conversion: a prognostic study. Br J Psychiatry 1980;136:548–51.
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