taking process.

“Everything counts” is the guiding principle. Each piece of information about the patient, from the time the appointment is made through the completion of the office visit, may help direct the examination. For example, in a tertiary neuro-ophthalmic practice, patients who wore sunglasses to their appointments were more likely to have nonorganic vision loss. Throughout the patient encounter, the patient’s general behavior and ocular capabilities should be observed continuously. Can the patient successfully ambulate into the room and into the chair? Can he or she find and shake the physician’s silently outstretched hand on arrival? Is there a problem with nonvisual tasks such as signing in at the front desk? Empathy, active-listening, and carefully recording the patient’s story allows for the doctor-patient relationship to be productive and nonconfrontational.

Suspicion increases if the ophthalmic examination does not uncover relevant objective abnormalities. A mismatch between objective and subjective examination findings is key. Examiners must be patient, persistent, and facile with the tests being used. The concept of misdirection is important. In other words, some examination techniques rely on the fact that the patient believes a particular eye or function is being tested as part of the normal eye examination, but in reality the examiner is trying to confirm a nonorganic disorder by demonstrating a nonphysiologic response, improved visual acuity, visual fields, or ocular motility.

A diagnosis of a nonorganic component can be confirmed when the patient does something that should not be possible based on the stated symptoms. Other tests may yield results that suggest the patient is not cooperating but do not prove a nonorganic disorder. The examination must be tailored to the individual and the specific complaints.

Although the scope and economic impact of nonorganic ophthalmic disorders are difficult to measure, somatic manifestations of psychogenic origin may account for at least 10% of patient visits to family physicians. In the mid-1980s, Keltner and coworkers estimated that fraudulent disability claims totaled $1 billion for a single year in the state of California, excluding the medical evaluation and legal fees. Clearly, extrapolating from these data, the cost to society of nonorganic ophthalmic disturbances is enormous.

Bengtzen R, Woodward M, Lynn MJ, Newman NJ, Biousse V. The “sunglasses sign” predicts nonorganic visual loss in neuroophthalmologic practice. Neurology. 2008;70(3):218–221.

Keltner JL, May WN, Johnson CA, Post RB. The California syndrome. Functional visual complaints with potential economic impact. Ophthalmology. 1985;92(3):427–435.

Kline LB. Techniques for diagnosing functional visual loss. In: Parrish RK II, ed. The University of Miami Bascom Palmer Eye Institute Atlas of Ophthalmology. Philadelphia: Current Medicine; 2000:493–501.

Miller NR. Neuro-ophthalmologic manifestations of nonorganic disease. In: Miller NR, Newman NJ, Biousse V, Kerrison JB, eds. Walsh and Hoyt’s Clinical Neuro-ophthalmology. 6th ed. Baltimore: Williams & Wilkins; 2005:1315–1334.

Examination Techniques

Numerous examination techniques are used with patients with nonorganic disorders. These techniques fall into 4 groups, depending on whether the disorders are of the afferent visual pathway, ocular motility and alignment, the pupils and accommodation, or eyelid position and function.

Afferent Visual Pathway

Selecting the appropriate tests of the afferent visual pathway depends on whether the dysfunction is a

visual acuity loss (complete or partial, bilateral or monocular) or a visual field defect.

Bilateral no light perception

Several tests, visual and nonvisual, are used when a patient reports complete bilateral blindness (ie, no light perception).

Nonvisual tasks Indirect evidence of a nonorganic component to complaints of total blindness arises from a patient’s inability to perform nonvisual tasks. Proprioceptive testing, such as failure to sign a paper or adequately perform a finger-to-nose test, in the absence of systemic neurologic diseases, should alert the clinician to problems (conscious or unconscious) with patient cooperation.

Pupillary reaction The presence of a normal pupillary reaction suggests that the anterior visual pathways are intact. However, it does not prove the loss is nonorganic, as there could be involvement of the bilateral anterior visual pathways or postgeniculate pathways (optic radiations or occipital cortex). An aversive light reaction by a patient who claims blindness establishes at least some level of afferent input.

Optokinetic nystagmus drum Perhaps the easiest test to perform with a patient who claims total blindness is to slowly rotate an optokinetic nystagmus (OKN) drum in front of the patient. If the patient claims to see nothing but the eyes move with the drum, a nonorganic component has been established. It is possible for malingerers to purposely minimize or prevent the response by looking around or focusing past the drum.

Mirror test The mirror test is extremely valuable in identifying visual function when no light perception is claimed. A large mirror is slowly rotated side to side in front of the patient. If the patient states that he or she sees nothing but the examiner notes eye movement with the mirror, then a subjective–objective mismatch has been documented (Fig 13-1).

Figure 13-1 Rotating a mirror in front of a patient who claims no light perception bilaterally produces shifts of ocular orientation in the direction of the mirror rotation. Such ocular movement demonstrates that the patient is capable of following his or her reflection. (Illustration b y C. H. Wooley.)

Electrophysiologic testing Visual evoked potentials (VEPs) play a limited role in assessing a possible nonorganic disorder. Both false-positive and false-negative results are possible with VEP testing, and the results are best used to confirm other findings, for example, the increased latency in organic disease. Normal VEP results for a patient who reports severe monocular or binocular vision loss and has normal clinical examination findings support the diagnosis of nonorganic disturbance of vision. An abnormal pattern-reversal visual evoked response in a patient with normal findings on neuro-ophthalmic examination should not, by itself, lead to the diagnosis of organic defect. Through a variety of techniques (eg, inattention, lack of concentration, meditation), a patient can willfully suppress a visual evoked response. See also “Visual evoked potential” in Chapter 3.

Morgan RK, Nugent B, Harrison JM, O’Connor PS. Voluntary alteration of pattern visual evoked responses. Ophthalmology. 1985;92(10):1356–1363.

Monocular no light perception

All of the tests described for bilateral no light perception may be performed unilaterally. Several additional approaches are possible, however, that involve ocular viewing confusion and tests that require binocularity.

Relative afferent pupillary defect In patients who claim complete vision loss in 1 eye only, other evidence to support optic nerve dysfunction, most often the presence of a relative afferent pupillary defect (RAPD), should be present (see Chapter 3). The absence of an RAPD substantially increases, but does not confirm, suspicion when eye examination findings are normal.

Base-out prism test A 4–6 prism diopters (Δ) prism is placed base-out in front of 1 eye with both eyes open; normally, this procedure elicits an inward shift of that eye (either as a conjugate saccade followed by a convergent movement of the opposite eye or by a convergent movement alone). Movement that occurs when the prism is placed over the “bad” eye indicates vision in that eye.

Vertical prism dissociation test A 4 prism is placed base-down in front of the “good” eye of a patient claiming monocular vision loss. If the subject has symmetric vision in both eyes, 2 images should be seen, one above the other. If the subject is able to see the letters only with the “good” eye, then only 1 image should be seen (Fig 13-2).

Figure 13-2 Monocular vertical prism dissociation test. With nonorganic vision loss, the patient will describe seeing 2 images, 1 over the other (A). True organic vision loss will render the patient unable to see the second image or to see only

a very blurred second image (B). (Courtesy of Lanning Kline, MD.)

Golnik KC, Lee AG, Eggenberger ER. The monocular vertical prism dissociation test. Am J Ophthalmol. 2004;137(1):135–137.

Confusion tests In confusion tests, the patient must be unaware of which eye is actually being tested. Tests must appear to be simply a normal part of the examination. Any suspicion on the part of the patient will be detrimental to the test interpretation.

In the fogging test, a trial frame is used. Plus and minus spheres (4–6 D) are placed in front of the “bad” eye, and plus and minus cylinders (4–6 D), with their axes aligned, are placed in front of the other eye. The patient is asked to read the chart while the front lenses are rotated. On the sphere side, rotation will make no difference, but on the cylinder side, vision will become severely blurred as the axes are rotated out of alignment. If the patient continues to read, he or she is doing so with the “bad” eye.

In the red-green test, duochrome (Worth 4-dot) glasses are placed over the patient’s eyes, with the red lens over the “bad” eye. The red-green filter is then placed over the Snellen chart, presenting

the letters simultaneously either on a green or a red background. The green lens will prevent the good eye from seeing the red background letters. If the red letters are read, the patient is reading with the “nonseeing” eye.

In the polarized lens test, the patient may wear the polarized lenses available with the stereoacuity test while reading a specially projected chart with corresponding polarized filters (Fig 13-3). Letters or lines may be selected that indicate the patient is reading with the “bad” eye.

Figure 13-3 Specialized polarized projector charts are obscured when a patient looks through 1 lens of the polarized glasses (A) but are visible when viewed through the other lens (B). (Courtesy of Steven A. Newman, MD.)

Stereopsis testing Stereopsis requires binocular vision. Patients may be tested with the standard stereoacuity test (using their appropriate near correction). Any evidence of stereopsis demonstrates there is vision in the “bad” eye. It should be noted that patients with vision in only 1 eye may well detect asymmetries in the first several circles on the basis of monocular clues. If the circle is “standing out from the page,” the patient has binocularity.

Monocular reduced vision

Patients reporting symptoms of reduced vision are more challenging. The clinician must convincingly demonstrate better visual acuity than initially claimed. Diagnosis of a nonorganic condition requires careful demonstration of a substantial difference between claimed and demonstrated visual acuity levels. Many of the tests described for patients with binocular or monocular no light perception can be applied to patients with monocular (and binocular) reduced vision.

Confusion tests The confusion tests described earlier in the “Monocular no light perception” section are useful if substantial reduction in visual acuity is claimed in 1 eye. The fogging test, redgreen duochrome test, and polarized lens test have the potential to give a quantitative visual acuity measurement if the patient is cooperative enough to continue reading. Unlike in the assessment of a patient who claims monocular blindness, simply demonstrating that the patient can read at all is not sufficient; the clinician must determine the actual visual acuity.

Although less common than visual acuity loss, complaints of difficulty seeing to 1 side are occasionally made by patients. The problem may be binocular but is more commonly unilateral. The field defects may take many forms but are most commonly nonspecific constrictions.

Automated perimetry testing The use of automated perimetry techniques has substantially improved standard visual field testing, but it is generally not helpful in distinguishing organic from nonorganic visual field loss. The machines are actually quite easy to fool. If motivated, a mildly sophisticated observer can reproduce homonymous defects, altitudinal defects, even arcuate and central scotomata. Nonetheless, central scotomata are extremely rare in nonorganic vision loss and warrant further evaluation. There are no characteristic changes in automated perimetry testing results that would confirm the suspicion of a nonorganic deficit. An unusual situation in which automated perimetry testing might be useful would be for a patient with a monocular defect that appears to respect the vertical midline. If repeating the field testing with both eyes open produces a similar, or even incomplete, defect, a nonorganic component is present (Fig 13-4).

Figure 13-4 “Missing half” field defect. A 33-year-old man complained of decreased vision temporally in the right eye after being in a motor vehicle accident. Automated perimetry testing demonstrates a normal field on the left (A) and a temporal defect on the right (B). Visual field tests performed with both eyes open (C) demonstrate persistence of the visual field defect, indicating a nonorganic basis for the visual complaint. (Courtesy of Karl C. Golnik, MD.)

Stewart JF. Automated perimetry and malingerers. Can the Humphrey be outwitted? Ophthalmology. 1995;102(1):27–32.

Confrontation testing In the case of a dense visual field defect, the patient is evaluated with confrontation testing. The area where the patient “can’t see” is carefully identified. Later, the patient is tested for “motility.” As part of this examination, stimuli are placed in various areas of the patient’s peripheral field, including those areas where the patient “couldn’t see.” Accurate saccades to these

nonauditory targets indicate an intact visual field.

In some cases, confrontation testing (“silent visual fields”) might initially appear to confirm a dense visual field defect. The patient is subsequently asked to count fingers in the “nonseeing” field, being instructed to report “none” when no fingers are seen. As the test progresses, the examiner begins showing fingers without saying anything. A response of “none” each time the fingers are put up confirms vision in that area.

Goldmann perimetry testing In Goldmann perimetry testing, the visual field is tested in a continuous fashion in a clockwise or counterclockwise direction starting with the I4e stimulus. A common nonorganic response shows a spiraling isopter getting closer and closer to fixation as testing continues. As larger stimuli (III4e and V4e) are employed, there is often further constriction, resulting in overlapping isopters (Fig 13-5). It is important to make sure there is no step across the vertical or nasal horizontal midline. A step across the midline may indicate that at least some physiologic component is present in the field abnormality.