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PubMed1999

[The diagnosis of psychogenic visual problems in children and young adults with application of visual evoked responses (VER)].

PURPOSE: To present diagnostical and therapeutical problems connected with children and adolescents suspected of aggravation or simulation of visual problems. MATERIAL: 5 patients between 10 and 13 years old with visual disturbances sent to ophthalmologist with suspicion of neuritis retrobulbaris or tumor cerebri. METHODS: Complexive diagnostical investigations (including visual field tests, color vision tests, visual evoked potentials) with complete ophthalmological examinations of visual organ and psychological evaluation of patients. RESULTS: The normal results of ophthalmological examinations and of all diagnostical investigations including visual evoked potentials. Psychological evaluation of patients showed psychological troubles of the young ones. CONCLUSIONS: The normal results of visual evoked potentials confirm the diagnosis of psychogenic visual disturbances and allow to save children before other medical invasive investigations. Such patients with psychogenic visual disturbances and their families usually need a special kind of psychogenic therapy.

Adolescent↗
PubMed1985

Functional visual field of patients with visual field loss.

To assess the capability of perceiving forms in patients with visual field loss, a concept of functional visual field was introduced based on determinations of the time required for pattern recognition. Two series of stimulus patterns were made of Japanese syllabic hiragana characters drawn with black dots in the background of open circles of various sizes: the clear stimulus had only open circles in the background and the noisy stimulus had black dots scattered in the background. The stimuli were presented for various durations to 15 normal subjects and 25 patients with narrowed visual field; a correlation of the percentages of correct pattern recognition with the stimulus durations permitted calculations of the 50% recognition time. The recognition time was longer with the noisy than with the clear stimuli. The recognition time with a given stimulus size was longer in patients than in normal subjects. In 3 normal subjects the visual field was artificially narrowed and the recognition time was determined. The recognition time could be expressed by a power function of the ratio of the effective visual field diameter to the diameter of the stimulus pattern. On this basis the functional visual field size of a patient was defined as the size of the artificially narrowed visual field of the normal subject that required the same recognition time as that of the patient. The functional visual field of patients could be correlated with the area of the perimetric field with the V/4 target of Goldmann's projection perimeter. The concept of the functional visual field was found to be useful to express the patients' capability for pattern perception.

Adult↗
PubMed1997

[Visual acuity measured by pattern visual evoked potential].

We investigated the appropriateness of a method for the assessment of visual acuity using pattern visual evoked potentials (PVEP) in which retinal X-ganglion cells are predominantly stimulated. Eighteen normal eyes (average 22.2 years old) with normal acuity of 1.0 were examined. The stimulus consisted of white and black checkerboards (39', 26', 15' and 9') with a visual angle of eight degrees and a contrast level of 15%. The pattern reversal frequency was 0.7 Hz. This resulted in 100 averaged PVEP per session. We judged visual acuity from responses of the P100 component. Visual acuity was judged to be 0.1, so that there was response to the 39' checkerboard stimulus pattern, but not to the 26' pattern. Consequently, the accuracy for visual acuity was 76.9% for 0.1, 71.4% for 0.2, 70.0% for 0.5 and 58.3% for 1.0. This method, which uses a stimulus pattern with a small visual angle, low contrast, and low pattern reversal frequency, is useful for subjective measurement of the visual acuity of infants or handicapped children whom it is difficult to measure by the conventional objective method of measuring visual acuity with Landolt's rings.

Adult↗
PubMed1998

Multifocal topographic visual evoked potential: improving objective detection of local visual field defects.

PURPOSE: To investigate the relationships between the pattern stimulation of different parts of the visual field (up to 25 degrees of eccentricity), the electrode position, and the cortical response to improve objective detection of local visual field defects. METHODS: The human visual evoked potential (VEP) was assessed using multifocal pseudorandomly alternated pattern stimuli that were cortically scaled in size. Monopolar and bipolar electrode positions were used. The visual field was investigated up to 26 degrees of eccentricity. Twelve normal subjects and seven subjects with visual field defects of different nature were studied. RESULTS: Although the monopolar response is heavily biased toward the lower hemifield, bipolar leads overlying the active occipital cortex (straddling the inion) demonstrate good signals from all areas of the visual field tested. The amplitude is almost equal for the averaged upper and lower hemifields, but the polarity is opposite, causing partial cancellation of the full-field VEP. The degree of cancellation depends mainly on latency differences between the vertical hemifields. The bipolar VEP corresponded well with Humphrey visual field defects, and it showed a loss of signal in the scotoma area. CONCLUSIONS: The multifocal VEP demonstrates good correspondence with the topography of the visual field. Recording with occipital bipolar electrode placement is superior to standard monopolar recording. To avoid a full-field cancellation effect, a separate evaluation of upper and lower hemifields should be used for the best assessment of retinocortical pathways. This technique represents a significant step toward the possible application of the multifocal VEP to objective detection of local defects in the visual field.

Adult↗
PubMed2003

Beyond visual acuity: new and complementary tests of visual function.

Visual acuity is an essential component of the routine ophthalmic examination and the most common measure of visual function. There is increasing recognition, however, of the need to evaluate visual function beyond the limited extent afforded by visual acuity. The primary objective of this article is to introduce a variety of new and lesser-used techniques for measuring visual function that complement visual acuity assessment, each of which has been shown to detect visual dysfunction in patients with normal visual acuity.

Color Perception↗
PubMed2000

Visual and non-visual cues in the perception of linear self-motion.

Surprisingly little is known of the perceptual consequences of visual or vestibular stimulation in updating our perceived position in space as we move around. We assessed the roles of visual and vestibular cues in determining the perceived distance of passive, linear self motion. Subjects were given cues to constant-acceleration motion: either optic flow presented in a virtual reality display, physical motion in the dark or combinations of visual and physical motions. Subjects indicated when they perceived they had traversed a distance that had been previously given to them either visually or physically. The perceived distance of motion evoked by optic flow was accurate relative to a previously presented visual target but was perceptually equivalent to about half the physical motion. The perceived distance of physical motion in the dark was accurate relative to a previously presented physical motion but was perceptually equivalent to a much longer visually presented distance. The perceived distance of self motion when both visual and physical cues were present was more closely perceptually equivalent to the physical motion experienced rather than the simultaneous visual motion, even when the target was presented visually. We discuss this dominance of the physical cues in determining the perceived distance of self motion in terms of capture by non-visual cues. These findings are related to emerging studies that show the importance of vestibular input to neural mechanisms that process self motion.

Acoustic Stimulation↗
PubMed2005

[Rapid onset of visual recovery following acute visual loss due to leber's hereditary optic neuropathy].

INTRODUCTION: Leber's hereditary optic neuropathy (LHON) is a maternally inherited disorder affecting the optic nerves in which the typical clinical presentation is subacute, painless, sequential visual loss in young adult males. Patients with LHON who have atypical clinical features may be initially misdiagnosed. OBSERVATION: An 8-year-old boy developed an acute severe bilateral optic neuropathy associated with pain and mild optic disc edema. Molecular genetic testing of his mitochondrial DNA revealed two point mutations, T14484C and G15257A. His vision began to improve within one month of onset of visual loss and eventually recovered to 20/15 in both eyes. Four years previously, his oldest sister had acutely lost vision in both eyes at age 12 years. Her young age, female gender, the bilateral visual loss associated with pain, optic disc edema, absent family history of visual loss and negative workup were felt to be most consistent with a clinical diagnosis of idiopathic optic neuritis of childhood. Her visual recovery which began within two months of visual loss further supported the diagnosis. She was retrospectively re-diagnosed with LHON after her younger brother was genetically confirmed. CONCLUSION: We describe two siblings with LHON whose time course from onset of visual loss to onset of visual recovery was unusually rapid. Because of other atypical features for LHON such as their young age at presentation, bilateral simultaneous visual loss and associated periorbital pain, their clinical profile appeared more typical of a demyelinating disease such as childhood optic neuritis. The first affected sibling (sister) was initially misdiagnosed. This report emphasizes that the clinical spectrum of LHON is variable and thus, LHON should be considered in any patient with an acute bilateral optic neuropathy, even in the absence of a positive family history. Correct diagnosis of this maternally inherited disorder is important for assessment of visual prognosis and appropriate genetic counseling.

Anti-Inflammatory Agents↗
PubMed2001

Neural model for processing the influence of visual orientation on visually perceived eye level (VPEL).

An individual line or a combination of lines viewed in darkness has a large influence on the elevation to which an observer sets a target so that it is perceived to lie at eye level (VPEL). These influences are systematically related to the orientation of pitched-from-vertical lines on pitched plane(s) and to the lengths of the lines, as well as to the orientations of lines of 'equivalent pitch' that lie on frontoparallel planes. A three-stage model processes the visual influence: The first stage parallel processes the orientations of the lines utilizing 2 classes of orientation-sensitive neural units in each hemisphere, with the two classes sensitive to opposing ranges of orientations; the signal delivered by each class is of opposite sign in the two hemispheres. The second stage generates the total visual influence from the parallel combination of inputs delivered by the 4 groups of the first stage, and a third stage combines the total visual influence from the second stage with signals from the body-referenced mechanism that contains information about the position and orientation of the eyes, head, and body. The circuit equation describing the combined influence of n separate inputs from stage 1 on the output of the stage 2 integrating neuron is derived for n stimulus lines which possess any combination of orientations and lengths; Each of the n lines is assumed to stimulate one of the groups of orientation-sensitive units in visual cortex (stage 1) whose signals converge on to a dendrite of the integrating neuron (stage 2), and to produce changes in postsynaptic membrane conductance (g(i)) and potential (V(i)) there. The net current from the n dendrites results in a voltage change (V(A)) at the initial segment of the axon of the integrating neuron. Nerve impulse frequency proportional to this voltage change signals the total visual influence on perceived elevation of the visual field. The circuit equation corresponding to the total visual influence for n equal length inducing lines is V(A)= sum V(i)/[n+(g(A)/g(S))], where the potential change due to line i, V(i), is proportional to line orientation, g(A) is the conductance at the axon's summing point, and g(S)=g(i) for each i for the equal length case; the net conductance change due to a line is proportional to the line's length. The circuit equation is interpreted as a basis for quantitative predictions from the model that can be compared to psychophysical measurements of the elevation of VPEL. The interpretation provides the predicted relation for the visual influence on VPEL, V, by n inducing lines each with length l: thus, V=a+[k(i) sum theta(i)/n+(k(2)/l)], where theta(i) is the orientation of line i, a is the effect of the body-referenced mechanism, and k(1) and k(2) are constants. The model's output is fitted to the results of five sets of experiments in which the elevation of VPEL measured with a small target in the median plane is systematically influenced by distantly located 1-line or 2-line inducing stimuli varying in orientation and length and viewed in otherwise total darkness with gaze restricted to the median plane; each line is located at either 25 degrees eccentricity to the left or right of the median plane. The model predicts the negatively accelerated growth of VPEL with line length for each orientation and the change of slope constant of the linear combination rule among lines from 1.00 (linear summation; short lines) to 0.61 (near-averaging; long lines). Fits to the data are obtained over a range of orientations from -30 degrees to +30 degrees of pitch for 1-line visual fields from lengths of 3 degrees to 64 degrees, for parallel 2-line visual fields over the same range of lengths and orientations, for short and long 2-line combinations in which each of the two members may have any orientation (parallel or nonparallel pairs), and for the well-illuminated and fully structured pitchroom. In addition, similar experiments with 2-line stimuli of equivalent pitch in the frontoparallel plane were also fitted to the model. The model accounts for more than 98% of the variance of the results in each case.

Humans↗
PubMed2003

End-diastolic and end-systolic volume from the left ventricular angiogram: how accurate is visual frame selection? Comparison between visual and semi-automated comnputer-assisted analysis.

BACKGROUND: End-diastolic (ED), end-systolic (ES) left ventricular (LV) volumes and LV ejection fraction (LVEF) are important parameters for clinical decision making in heart disease. In clinical practice the frames from cine-angiography with the largest and smallest opacified LV areas are visually selected and the endocardial borders traced as LVED and LVES contours, respectively. We compared the accuracy of this visual method using two frames with a semi-automated computer assisted frame-by-frame analysis of the complete opacified cardiac cycles. METHODS AND RESULTS: In 17 patients a biplane LV cine-angiogram was obtained at 25 frames/s. Complete frame-by-frame analysis was performed using semi-automatic border detection software. Experienced independent observers visually selected and manually traced LVED and LVES in the so-called visually assessed two-frame method in a consensus meeting. LV volumes were calculated by the area-length method. Mean LVEDV, LVESV and LVEF were 133 +/- 57, 56 +/- 40 ml and 61 +/- 16%, respectively, for the visually assessed two-frame method, and 117 +/- 49, 53 +/- 33 ml and 60 +/- 13%, respectively, for the semi-automated computer assisted frame-by-frame method. LVEDV was significantly higher in the visually assessed two-frame method (p < 0.01). Linear regression analysis showed an excellent correlation between semi-automated computer-assisted frame-by-frame and the visually assessed two-frame LVEDV (y = 1.2x - 2.9; r2 = 0.98), LVESV (y = 1.2x - 8.2; r2 = 0.97) and good linear correlation for LVEF (p = 1.2x - 3.6; r2 = 0.82). Bland-Altman analysis showed respectively a bias of 16.4, 2.4 ml and 5.0% with overall wide limits of agreement (-6.6 and 39.4 ml; -16.6 and 21.4 ml; -9.0% and 19.1%). CONCLUSION: Correlation is excellent when visually assessed LVED and LVES are compared with a semi-automated computer assisted frame-by-frame analysis. However, the visually assessed two-frame method tends to overestimate the volumes obtained by semi-automated computer-assisted frame-by-frame analysis, especially for LVEDV, indicating that visual selection will yield a higher LVEF, which may influence clinical decision making.

Angiocardiography↗
PubMed2001

Causes of severe visual impairment and blindness in children attending schools for the visually handicapped in the Czech Republic.

AIMS: To describe the causes of severe visual impairment and blindness in children in schools for the visually handicapped in the Czech Republic in 1998. METHODS: Pupils attending all 10 primary schools for the visually handicapped were examined. A modified WHO/PBL eye examination record for children with blindness and low vision was used. RESULTS: 229 children (146 males and 83 females) aged 6-15 years were included in the study: 47 children had severe visual impairment (20.5%) (visual acuity in their better eye less than 6/60), and 159 were blind (69.5%) (visual acuity in their better eye less than 3/60). Anatomically, the most affected parts of the eye were the retina (124, 54.2%), optic nerve (35, 15.3%), whole globe (25, 10.9%), lens (20, 8.7%), and uvea (12, 5.2%). Aetiologically (timing of insult leading to visual loss), the major cause of visual impairment was retinopathy of prematurity (ROP) (96, 41.9 %), followed by abnormalities of unknown timing of insult (97, 42.4%), and hereditary disease (21, 9.2%). In 90 children (40%), additional disabilities were present: mental disability (36, 16%), physical handicap (16, 7%), and/or a combination of both (19, 8%). It was estimated that 127 children (56%) suffer from visual impairment caused by potentially preventable and/or treatable conditions (for example, ROP, cataract, glaucoma). CONCLUSIONS: Establishing a study group for comprehensive evaluation of causes of visual handicap in children in the Czech Republic, as well as for detailed analysis of present practice of screening for ROP was recommended.

Adolescent↗
PubMed1986

Visual dominance in the cross-modal kinesthetic to kinesthetic plus visual feedback condition.

In previous studies subjects who have learned a positioning response with kinesthetic feedback tended to make greater errors when visual feedback was provided during later trials. These subjects have always performed with both kinesthetic and visual feedback available. This study determined whether subjects with only visual feedback would produce errors similar to those who received kinesthetic plus visual feedback. Blindfolded subjects learned to move a handle to a criterion location with knowledge of results following each trial. Subjects then were assigned to one of three experimental groups, with only kinesthetic feedback, with kinesthetic plus visual feedback, or with only visual feedback. Subjects had 9 trials without knowledge of results in these feedback conditions. When visual feedback was available, subjects tended to make longer response errors. This finding replicates previous studies. Also, the similarity of performances from the conditions with visual feedback indicated the dominance of visual information in the condition with kinesthetic plus visual feedback.

Feedback↗
PubMedDate not supplied

[The effect of early visual deprivation on the level of N-acetyl-1-asparaginic acid and the activity of phosphate-activated glutaminase in visual analyzer structures and various regions of the dog cerebral cortex and cerebellum].

Under conditions of 45-days visual deprivation content of N-acetyl-L-aspartic acid was considerably increased in visual cortex (field 17) tissues and decreased in the superior colliculus and exterior geniculate body. At the same time, content of N-acetyl-L-aspartic acid was not altered in the visual cortex mitochondrial fraction; in the outer structures studied level of this amino acid was distinctly decreased both in tissues and mitochondrial fractions. After prolongation of the visual deprivation up to 90 days content of N-acetyl-L-aspartic acid was sharply decreased in tissues and mitochondrial fractions of all the formations studied of dog brain visual analyzer. The maximal 4.5-fold decrease was found in mitochondrial fractions of the visual analyzer (field 17), in the exterior geniculate body and superior colliculus content of the amino acid was decreased 2.4-3.9-fold as compared with controls. In 90 days-long visual deprivation total activity of phosphate-dependent glutaminase was considerably increased (1.18-3.71-fold as compared with controls) in myelinic (A), membraneous (B), light (C), and heavy synaptosomal and synaptic mitochondrial (E) subfractions of the visual cortex (field 17). The rate of the enzyme activation was distinctly higher in these subfractions as compared with that of the motor and parietal cortical subfractions. After 90 days-long visual deprivation the similar alterations were found in A, B, D and E cerebellum subfractions but these alterations were less distinct as compared with the visual, motor and parietal subfractions.

Animals↗
PubMed2005

Complex visual hallucinations in the visually impaired: a structured history-taking approach.

OBJECTIVE: To study complex visual hallucinations in visually impaired individuals. METHODS: A prospective comparative study involving structured history taking and cognitive assessment in 48 consecutive visually impaired individuals with best-corrected visual acuity of 20/200 or worse and an age-matched cohort of 48 consecutive patients with visual acuity of 20/40 or better in at least 1 eye. RESULTS: Thirty visually impaired subjects (63%) experienced hallucinations, unrelated to specific ocular pathology. None volunteered the symptom; 2 admitted hallucinations on nonleading questioning and 28 on direct questioning. All displayed insight into the unreality of their hallucinations, although 18 (60%) achieved this after initial deception. Seventeen (57%) expressed concern; 7 (23%) experienced disturbing images. Nineteen (63%) feared being labeled as insane were they to admit to hallucinations, while 10 (33%) were fearful of impending insanity. Sixteen (94%) of 17 concerned patients derived comfort from sympathetic reassurance that their hallucinations did not represent sinister pathology. In contrast, none of the individuals with normal vision experienced any hallucinations (P<.001). Cognition was intact in all groups. CONCLUSIONS: Complex visual hallucinations with insight commonly occur in visually impaired, cognitively intact individuals due to acquired visual impairment and are unrelated to chronological age. Hallucinatory experiences are almost invariably admitted to only on direct questioning, due to fears of being considered insane. Although generally pleasant, hallucinations may cause distress, because of content or implications of the hallucinatory activity. Sympathetic explanation affords significant emotional relief.

Adult↗
PubMed1984

Visual results after microsurgical removal of meningiomas involving the anterior visual system.

Visual results were evaluated in 20 patients after microsurgical removal of intracranial meningiomas that had produced visual loss from damage to the anterior visual system. Patients were evaluated preoperatively, immediately postoperatively, and several months to years after surgery. Visual acuity either improved or remained normal in 68.75% (22/32) of eyes examined and worsened in 25% (8/32) of eyes examined. Visual field changes generally paralleled visual acuity changes. Visual results were most closely related to duration of visual symptoms and not to either tumor size or preoperative visual findings.

Adult↗
PubMed1991

Selective attention modulates extrastriate visual regions in humans during visual feature discrimination and recognition.

Positron emission tomography (PET) was used to identify regions of the human visual system which were selectively modulated by attention during feature discrimination and recognition tasks. In a first experiment, subjects were cued to the shape, colour or speed of visual stimulus arrays during a same-different match-to-sample paradigm. The psychophysical sensitivity for discriminating subtle attribute variations was enhanced by selective attention. Correspondingly, the neural activity (as measured by blood flow changes) in different visual associative regions was enhanced when subjects attended to different attributes of the same stimulus (intraparietal sulcus for speed; collateral sulcus and dorsolateral occipital cortex for colour; collateral sulcus, fusiform and parahippocampal gyri, superior temporal sulcus for shape). These regions appeared to be specialized for processing the selected attribute. Attention to a visual feature, therefore, enhances the psychophysical sensitivity as well as the neural activity of specialized processing regions of the human visual system. In a second experiment the effect of target probability (which biases attentional selection) was studied during visual search tasks involving the recognition of a single-feature (i.e. colour) or a feature-conjunction (i.e. colour x orientation) target. Target probability positively modulated neural activity of extrastriate visual regions, which were related to the single-feature or feature-conjunction processing level. These results suggest that selective attention can influence different processing levels in the visual system, possibly reflecting a facilitatory effect on different visual computations or task components.

Attention↗
PubMed1992

Use of 10-Hz flash visual evoked potentials in prediction of final visual acuity in diabetic eyes with vitreous hemorrhage.

In 44 diabetic eyes with vitreous hemorrhage, monocular steady-state visual evoked potentials were elicited through closed eyes by a 10-Hz flash. Visual evoked potentials were rated as normal or abnormal on the basis of amplitude and waveform. Abnormal visual evoked potentials were subdivided into mildly abnormal, markedly abnormal and nonrecordable categories. Patients with normal potentials were predicted to have visual acuities of 6/15 (20/50) or better. Patients with abnormal potentials were predicted to have visual acuities of 6/18 (20/60) or worse. Final visual acuities were the best visual acuities recorded in the 6 months after vitreous surgery (vitrectomy) or spontaneous clearing of the vitreous hemorrhage. The visual evoked potential categories and final acuities were compared with a 2 x 2 contingency table. The accuracy was 86%. The visual evoked potential categories and final acuities were associated at a statistically significant level.

Adult↗
PubMed2005

Visual acuity and perimetry as measures of visual function in diabetic macular oedema.

AIMS/HYPOTHESIS: We examined to what extent visual acuity and perimetric sensitivity as measures of central and paracentral visual function would be useful for evaluating the presence and severity of diabetic macular oedema. MATERIALS AND METHODS: We evaluated 59 eyes of 59 diabetic patients by identifying the presence (n=20) or absence (n=39) of macular oedema on stereo fundus photographs. The area of oedema and its distance to the centre of the macula were measured. Ischaemic macular damage was quantified by measuring the foveal avascular zone and adjacent perifoveolar intercapillary areas on fluorescein angiograms. Visual function was assessed by visual acuity charts and by short-wavelength perimetry and standard white-on-white perimetry of the central 10 degrees field. RESULTS: Visual acuity did not differ between eyes with and without macular oedema. In eyes with oedema, visual acuity was correlated to the distance of the oedema from the centre of the macula (log of minimum angle of resolution {LogMar} score decreased by 0.15/mm; p=0.006) and to the thickness of the retina when the centre was affected (LogMar score decreased by 0.003/mum of thickness; p=0.0002). Multivariate analyses confirmed the results (R (2)=0.46 and 0.77, respectively). Short-wavelength perimetry sensitivity was more depressed in eyes with oedema (p=0.033) but was not significantly associated with the presence of oedema after correction for macular ischaemic damage. There was no correlation between these field defects and the severity of oedema. CONCLUSIONS/INTERPRETATION: Visual acuity was a useful measure of visual function in diabetic macular oedema involving the centre. Visual field defects were more common in eyes with macular oedema but reflected ischaemic damage of the macula rather than macular oedema itself.

Adult↗
PubMed2006

Recording of both VEP and multifocal ERG for evaluation of unexplained visual loss electrophysiology in unexplained visual loss.

The purpose of this retrospective study was to determine the relevance of both visual-evoked potentials (VEP) and multifocal electroretinography (mfERG) to evaluate unexplained visual loss. Seventy-two consecutive patients (1996-2002) with visual disturbances of unknown origin underwent both VEP and mfERG (ISCEV standard). The mean age was 42.4 years (11.8-74.5) and median visual acuity 0.5 (no light perception - 1.0). Symptoms reported included visual acuity loss (n=69), visual field defects (n=11), disturbances of colour vision, light or dark adaptation (n=10). VEP and mfERG were normal in 43% (n=31). Both VEP and mfERG were pathological in 24% (n=17). In a further 18% (n=13) only the mfERG was pathological and in 15% (n=11) only the VEP was pathological. Macular dysfunction as detected with mfERG was present in 73% of 41 patients with at least one pathological test. Neuroimaging (MRI, CCT) and/or neurological examination was performed in 27/72 patients (38%), to account for unexplained visual loss, prior to the electrophysiological tests; these were normal in all patients. Electrophysiological tests revealed disturbances of the post-retinal visual pathway in only 3/27 patients. In 12/27 patients, mfERG revealed a macular disorder; in a further 12/27 patients VEP and mfERG were normal. The combined evaluation of VEP and mfERG is useful both to establish the area of dysfunction and the normality of the visual system. Electrophysiological testing prior to neuroimaging is recommended for patients where clear clinical signs of cerebral disorders are not evident. This reduces the frequency of unnecessary neuroimaging and associated radiation exposure.

Adolescent↗