There are two principle aims in the initial clinical assessment of a child with suspected nonorganic visual loss. The first is a thorough clinical examination to exclude obvious organic disease. The second is demonstration that visual function is better than claimed (or is indeed normal) or that the claimed visual symptoms are non-physiologic. This depends on the child being unaware that the responses given to examination tests are not consistent with the level of visual function initially claimed and a lack of knowledge of the normal physiology of the visual system . On occasion, clinical assessment will need to be supplemented by further investigation. Flexibility in assessment is also essential as it is not always apparent at first meeting the child and guardians that nonorganic visual loss is a diagnostic possibility. Different strategies are utilised depending on the laterality and severity of claimed vision loss.

Sir Stewart Duke-Elder emphasized the importance of clinical skill in his statement; “One point is important: the examiner should know thoroughly the tests he proposes to carry out, for the most important feature in such testing is the rapid and sure manipulation; few succeed unless they are well prepared.” [42] It is vital that the examination procedure appear routine and that the child be unaware that the examiner is attempting to demonstrate improved visual function [43, 44]. Drews suggested that the tests utilised in assessment of nonorganic visual loss be practiced with routine patients to improve skill and create awareness of usual responses [43]. The importance of a neutral and non-judgemental attitude has been emphasised by many authors [5, 43, 45, 46]. It is important that the ophthalmologist not demonstrate any irritation nor lose patience with a child during the course of assessment. An attitude of friendly encouragement is most likely to gain optimal cooperation.

Routine historical information should be acquired from the child and guardians. Often the most striking feature of the history is the child’s apparent indifference to their symptoms. This la belle indifference is frequently noted and is more often seen in cases of so called “hysteria ” than malingering. On occasions it is evident that parental anxiety with regard to the symptoms is greater than that of the child. This may especially be the case if there have been previously inconclusive assessments prior to the current consultation.

On specific questioning there may be inconsistencies related to visual activities. A child may describe poor visual function yet not experience any difficulty with reading or playing games on an electronic device. School work or performance may or may not be adversely affected.

It is possible that not all of the relevant history will be obtained initially. This particularly applies to the psycho-social aspects of the history that may not be fully explored until the possible nonorganic nature of the presentation is becoming apparent. There is often some benefit in interviewing the parents or guardians separately from the child to obtain this history. Such enquiry should be open-ended such as: “Are you aware of any problems at school?” or “Have there been any events or stresses at home?” Significant stressful events such as bullying, death of a relative or parental separation may then become evident that may not have seemed relevant earlier in the consultation. A careful family history for significant ophthalmic disease may help explain the source of a child’s visual symptoms. Holden and Duvall-Young reported three children with a family history of retinitis pigmentosa and nonorganic symptoms closely resembling those of retinitis pigmentosa [47]. Skoog et al. reported similar observations in their series of patients seen at a Swedish diagnostic center for retinal degenerations and dystrophies [48].

Initial clinical examination is directed at the detection of organic pathology that would explain the presenting symptoms. Once excluded, the aim of clinical examination switches to the demonstration that visual function is better than claimed (and, if possible, that it is normal) or that claimed visual symptoms are non-physiologic. An example of the former would be demonstration of normal visual acuity with a “trick refraction” such as plano lenses which are presented with the suggestion that they are a true glasses prescription. An example of the second would be the demonstration of a spiral visual field on perimetry.

Many reports have emphasised the importance of initially observing the child move around the waiting and examination rooms [5]. This is relevant for the occasional child who is claiming bilaterally and significantly reduced visual acuity or field. The observation that such a child moves freely is suggestive that visual function is better than claimed but cannot be taken as positive proof that this is the case as some children with severe organic impairments can be remarkably adaptive, especially when the changes are chronic rather than acute. Acute discovery of a chronic organic symptom , previously not reported by the child, must be considered.

A comprehensive review of clinical examination methods for both children and adults with nonorganic visual loss is available in the monograph of Enzenauer et al. [5]. The following discussion is limited to the clinical tests that are useful in the assessment of children and are in common usage. Clinical tests to be considered are listed in Table 17.4.

The order in which the various tests are used to distinguish organic and nonorganic disorders is largely determined by the severity and laterality of claimed visual loss. As visual field defects are infrequently symptomatic in children and visual field testing is inherently difficult at younger ages such testing is often performed later in the assessment to confirm non-physiologic nature of a patient’s symptoms.

Eliciting the pupil response is a measure of the integrity of the afferent visual pathway. In cases of organic bilateral severe visual loss (no perception of light) anterior to the chiasm bilateral amaurotic pupil responses will be seen. Normal pupil responses indicate either post chiasmic disease or a nonorganic disorder.

The presence of optokinetic nystagmus (OKN) is indicative of some visual function. A large mirror positioned directly in front of the patient and then slowly tilted around either the horizontal or vertical axis will induce involuntary following eye movements in almost all sighted individuals thus providing proof of some level of vision. Unexpected visual stimuli such as a sudden threatening movement or ridiculous facial expression of the part of the examiner will often elicit a response from a child that can only be the result of a visual response. Although the presentation of printed profanity as a method of eliciting a startle response has been used in adults, discretion is perhaps warranted when considering this technique in a child. Placing a small base out prism in front of either eye may induce a fusion response that is also evidence of vision. Tests that are not perceived by the patient as tests of visual function such as preferential looking test may elicit a response [34]. Finally tests of proprioception, such as touching both index fingers tip to tip in front of the face, may be mistakenly believed to require visual input and thus be paradoxically poorly performed by an individual with nonorganic visual loss. In reality a child with newly acquired severe visual loss will be able to perform such test quite well.

The absence of a relative afferent pupil defect is very suggestive that vision is better than no perception of light. All other tests used above for a child claiming binocular total loss of vision can be used for a child claiming unilateral total loss of vision. The better seeing eye is occluded and the test then performed. In some cases when performing the base out prism test it may be better to use a stronger prism (25∆) and observe to see if there is an induced refixation movement rather than looking for the small fusional movement induce by a 4–6∆ base out prism.

Refractive trickery is useful in cases of unilateral or bilateral reduced vision more than reported no perception of light. A detailed discussion of the history and attribution of tests used in refractive trickery is beyond the scope of this text. For readers requiring further information should consult Functional Ophthalmic Disorders by Enzenauer et al. [5]. The principle is to suggest to the child that the refractive correction, provided either in trial lenses or the phoropter, will improve the vision when in fact it should not, or to suggest to the child that they are using a better eye when in fact they are using the weaker eye. These techniques tend to be particularly useful when a child responds positively to a query about whether they are interested in obtaining glasses, particularly at times when wearing glasses is considered fashionable or another family member has received attention around the receipt of new glasses.

One technique of refractive trickery is to induce optical blur for both eyes and then, unbeknown to the child, gradually lessen this blur for one or both eyes while encouraging the child to read further down the vision chart. It is important that the changing of lenses is done smoothly. It is often helpful to obscure the child’s view of the vision chart while such manoeuvres are performed. The examiner should encourage the child throughout this procedure and stress that the glasses being tested are very powerful and the vision test is becoming easier. This takes advantage of the child’s suggestibility. In cases of unilateral blindness the better seeing eye is left blurred while blur for the reportedly worse eye is gradually reduced. Blur is most commonly with a hypermetropic over correction or cross cylinder (equal but opposite sign cylindrical lenses with axes at 90⁰). The power of the blurring lens must be sufficient to achieve an expected acuity less than the reportedly worse eye. Thus, this test is best performed after cycloplegic refraction to allow for knowledge of the correct refraction of both eyes. The blur of cycloplegia may also be useful as it can cause some confusion for the child and the relief of this blur may induce the child to see better than earlier in the assessment process. It is important to observe the child, especially if using a phoropter, to note if there is alternate eye closure occurring. Such behaviour may be used in an older child to check which eye is being tested and is said to be utilised by adults who are malingering and attempting to foil the examiner’s trickery [49].

Stereopsis is dependent of both eyes seeing and thus the finding of stereopsis implies both eyes can see. This test depends on the subject being ignorant of this physiologic fact. Verhoeff in 1942 showed that high grade stereopsis correlated with good and equal vision [50] and Levy and Glick correlated levels of visual acuity with measured stereopsis using the Titmus Stereo Test™ (Stereo Optical, Chicago, Illinois, USA) in 1974 [51]. In this study normal subjects were tested and monocular blur was used to induce reduced visual acuity in one eye and stereopsis was measured at different levels of reduced visual acuity. The correlation found by Levy and Glick are tabulated in Table 17.5. The stereo fly can also be useful in a child presenting with a complaint of bilateral blindness as it may induce a startle response indicative of vision, similar to those tests described above.

Colored filters that dissociate the visual input to either eye are useful in detecting claimed total blindness in one eye. Herman Snellen is credited with being the first to suggest colored filters for this purpose [5]. With red and green filters in front of either eye the child is then asked to read the letters on a duochrome chart or read a word (such as FRIEND) in which alternate letters are green or red or view the Worth 4-dots. If the child reads the entire duochrome line or word or counts 4 lights they have vision in both eyes and if using a particular line on a Snellen or picture chart, one establishes the acuity in both eyes.

Down up refraction (sometimes referred to as “doctor killing refraction” or “toothpaste refraction”) is measuring acuity starting from the bottom of the acuity chart with the smallest optotype and gradually asking the subject to read successively larger lines. The origin of this term is obscure but the meaning is readily apparent when one considers the time that may be required to do this test. This test required significant patience and encouragement on the part of the examiner. It is important to stress how easy each line is to read. Its success with children depends on their suggestibility.

Ishihara line tracing was described by Bourke and Gole [52] as ancillary test for nonorganic visual loss. These authors observed that some children with nonorganic visual loss claimed not to be able to read the numbers on an Ishihara test but were able to trace the winding lines on the plates designed for innumerate individuals. This response is clearly non-physiologic. These authors also noted that some children show inconsistency when reading the Ishihara plates through a red filter [52]. When viewing the Ishihara plate through a red filter all numbers are visible even if there is a color vision defect. Bourke and Gole described a 17 year old girl who claimed to be unable to see the numbers (other than the initial test plate) both without and with a red filter which is a non-physiologic response.

Visual field testing may be used to detect non-physiologic field loss in cases of claimed unilateral total blindness. Osako et al. demonstrated abnormalities in monocular static perimetry in children with nonorganic visual loss [53]. These authors were comparing normal children with children confirmed to have nonorganic visual loss. Smith and Baker suggested that standard static perimetry is unable to satisfactorily distinguish nonorganic and organic causes of field loss when the fields of a group of patients with known organic field loss were compared with a group of patients with nonorganic visual loss [54]. Martin modified a Humphrey Field Analyser™ (Carl Zeiss Meditec AG, Jena, Germany) so that static perimetry could be performed on both eyes simultaneously [55]. He was able to demonstrate significant differences if the patient was instructed that the “bad” eye was being test compared with when the “good” eye was being tested and that these differences were non-physiologic confirming the finding of nonorganic visual loss. Unless the method of Martin [55] is used, some caution should be taken when interpreting static perimetry in children with suspected nonorganic visual loss. Rather, confrontation technique (as described above for reported tunnel visual fields) or tangent screen, may be more useful in detecting nonorganic visual field loss.

Ali has described a simple and useful technique to distinguish organic and nonorganic constricted visual fields with the Goldman perimeter [56]. This technique compares the size of the constricted field measured with standard steady fixation and kinetic perimetry (target moving peripheral to central) with the field measured with the subject instructed to follow the light until it disappears from view while the target is moved from the central visual field in a peripheral direction. The field measured with eye movement is called the “uniocular field of fixation”. Normal physiology would dictate that the uniocular field of fixation (with eye movement) is larger than the field measured with standard steady and central fixation. Ali clearly demonstrated that in individuals with organic causes for field constriction the uniocular field of fixation was larger as would be expected while in individuals with nonorganic field constriction the uniocular field of fixation remained the same size or indeed smaller [56]. We have found this simple perimetry technique useful in diagnosing nonorganic field defects.

Scott and Egan have drawn attention to the fact that the presence of a central scotoma is likely to have an organic cause, even if there are other features that suggest a nonorganic diagnosis [40].

Perimetry has a long history in the assessment of nonorganic visual loss [15]. Tangent screen testing of visual fields in cases of nonorganic visual loss was first used in the nineteenth century and has been used to document non-physiologic or field defect such as spiralling isopters and tubular fields.

Further investigation. The decision to initiate further investigation can be difficult. In younger children with suspected nonorganic visual loss this decision may be further complicated by the need for general anesthesia to do so. Some authors have extensively used electrophysiology and neuroimaging in all patients with suspected nonorganic visual loss regardless of clinical findings [4, 35]. Some may feel compelled to do so out of medicolegal concerns. Others suggest further investigation only if there is uncertainty of diagnosis after clinical assessment [24, 27]. If uncertainty remains, another option may be to re-examine the child after a period of time without further intervention or testing and then only proceed with further investigation if the symptoms do not resolve spontaneously. It can be difficult for a child to maintain a purposeful falsehood in the absence of true chronic psychiatric disease. Electroretinogram, fundus autofluorescence, and optical coherence tomography may be a particularly useful tests to detect signs of retinal dystrophy or other subtle foveal pathology in cases where there is uncertainty [57–59].

Visual evoked responses (VER). The first reports of the use of VER in detecting nonorganic visual loss appeared in 1960s [60–62]. Potts and Nagaya reported on three (presumably) adult patients with “hysterical amblyopia” and demonstrated normal light adapted flash VER despite the claim of reduced vision [61]. Krill reported 23 patients (15 of whom were age 16 years and younger) with “hysterical amblyopia” based on the finding of reduced visual acuity and/or abnormal visual fields [62]. Krill noted abnormal dark adaptation with abnormally elevated final dark adaption thresholds in 13 of 23 subjects and an upward shift of the final dark adaptation threshold on prolonged testing in 19 of 23 despite normal ERG and VER [62]. It was suggested that this upward deflection of dark adaptation threshold on prolonged testing (called the “exhaustion phenomenon”) may be unique to “hysterical amblyopia” [62]. Behrman reported a larger series of 35 patients 51 % of whom were under 16 years old [60]. Many of Behrman’s patients presented with constricted visual fields and paradoxically normal electroretinograms with abnormal dark adaption curves [60]. In these patients she undertook dark adapted flash VER which was normal prompting her to suggest that “A normal dark-adapted VER, recorded despite a poor subjective dark-adaptation curve, is at present the best indication of hysterical amblyopia” [60].

Pattern VER has supplanted flash VER as the method of choice of recording VER in cases of suspected nonorganic vision loss [63]. Other authors have published reports cautioning against the reliability of both dark adaptation [64] and VER in the diagnosis of nonorganic vision loss [65, 66]. Both Bumgartner et al. and Morgan et al. demonstrated normal adults are consciously able to alter or suppress pattern VER [65, 66]. Saitoh et al. reported that pattern VER is supranormal in all age groups of subjects with “psychogenic visual disturbance” and were unable to offer an explanation for this observation but cautioned that it may be the result of some as yet unrecognised abnormality in the visual pathway [67]. These authors reported that in the case of malingers (all of whom were adults) the VER was subnormal [67]. They suggested that malingers shifted fixation to disrupt the testing process to create an invalid result. The high rates of normal pattern VER in children with nonorganic vision loss reported by some authors suggests that the value of this test may be greater in children [67–69]. This is presumably related to higher compliance with fixation during testing and a low incidence of malingering in children.

Modification in recording techniques has been reported to increase the reliability of VER in detecting nonorganic visual loss. In particular sinusoid patterns [70], step VER (using multiple recording channels) [71, 72], multifocal VER (using both multiple recording channels and multiple stimulation positions across the central visual field) [73] and pattern appearance VER [74] have been described as improvements. Wright et al. have demonstrated that chloral hydrate sedation has a minimal effect on pattern VER and may be a useful technique in uncooperative children [75].

The differential diagnosis of nonorganic visual loss includes those disorders that give rise to visual loss without an obvious ocular explanation. These include early cone or cone-rod dystrophies, Leber congenital amaurosis, achromatopsia (although nystagmus and photophobia usually present), early Stargaardt disease, congenital stationary night blindness (although high refractive error often present), amblyopia, paraneoplastic and autoimmune retinopathy (much more frequent in adults), retrobulbar optic nerve disease (without optic atrophy) and central defects from the chiasm posteriorly. Clinically many of these disorders will be readily distinguished with findings such as a relative afferent pupil defect or a true homonymous hemianopia in retrobulbar disorders .

Misdiagnosis of organic disease as nonorganic visual loss has rarely been reported in children and is worthy of consideration. Krill and Newell reported 2 of 59 patients (34 of whom were <18 years old) who developed organic disease after an initial diagnosis of nonorganic visual loss [19]. One developed “macular degeneration” and the second unilateral optic atrophy and “was thought to have early multiple sclerosis.” The age of these patients was not stated in the report. Rada et al. reported three children who had no evidence of organic disease initially and these authors suggested that the organic disease may have been co-existent or incipient with the possibility that the true nature of the disease was “initially masked by emotional aspects” [41] Two of these patients are described in detail and both had macular pathology and one had a central scotoma at presentation. Scott and Egan reported a 14 year old boy who was diagnosed as having nonorganic visual loss on the basis of Titmus test stereopsis of 40” of arc despite have best recorded visual acuities of 20/70 and 20/60 and an otherwise entirely normal examination [40]. This boy was subsequently found to have an abnormal multifocal electroretinogram and was diagnosed as having a cone dystrophy. More recently Lim et al. have reported two children aged 11 and 16 years who were found to have Stargardt disease and cone dystrophy respectively on investigation for persistent unexplained “nonorganic” visual loss [10]. The 11 year showed a central scotoma on automated perimetry and had mild temporal disc pallor at presentation both of which call into question the initial diagnosis of nonorganic disease. These authors also reported a 21 year old woman who presented with sequential bilateral visual loss with fluctuating vision who was treated as having “optic neuritis” with no other supporting features on extensive investigation. Subsequent testing revealed a diagnosis of Leber hereditary optic atrophy [10].

The most common management strategy used with children with nonorganic visual loss is simple reassurance [26–28, 41, 76]. This advice is primarily based on the excellent spontaneous resolution rate found in most studies [10, 24, 27, 28, 36, 41]. It has been suggested that this management can be undertaken by “an interested and concerned ophthalmologist who provides both the parents and the child reassurance and the opportunity to discuss sources of conflict.” [41] It is recommended that the child not be confronted with the nonorganic nature of the symptoms [26, 77], although there may be some advantage to having a discussion in front of the child indicating the “good news” that they are normal and their symptoms will resolve thus ensuring parent and child are “on the same page”. It is considered important to leave the child with a diplomatic “way out” [78]. Several authors have advised against placebo therapy, even for short periods of time because of concern of reinforcing the concept of organic disease for both parents and child [21, 41].

Other physicians believe that a discussion of the diagnosis and management plan with the parents or guardians without the child present is recommended. In either plan, it is important that the parents have a clear understanding of diagnosis that is being suggested. Many parents are relieved by this news but some may be confused or even frustrated and angry with their child for causing distress and anxiety [26]. It is vital that the parents are made aware of the unconscious processes that give rise to this scenario. The parents are an important part of the process of reassuring the child and they might also be made aware of the warning signs of non-resolution of symptoms, development of other nonorganic somatic complaints, and the identification of potential stressors in the child’s life that may not yet have come to light, particularly if such warning signs occur.

Psychiatric referral is not required for self-limiting presentations. In children that have persisting symptoms these are often mild and have a limited impact on daily function [36, 41]. Patients who have a prolonged clinical course, ongoing disability, multiple nonorganic somatic symptoms or the possibility of psychological comorbidity may benefit from psychiatric assessment. This assessment should include an assessment of comorbid anxiety or depressive conditions, possible underlying background psychological stress and family functioning. It may also require an assessment of possible secondary gains that the patient may be receiving from their symptoms [79]. In this situation the diagnosis may be a factitious disorder and this is discussed in more detail below.