Visual processing speed in hemianopia patients secondary to acquired brain injury: a new assessment methodology.

BACKGROUND: There is a clinical need to identify diagnostic parameters that objectively quantify and monitor the effective visual ability of patients with homonymous visual field defects (HVFDs). Visual processing speed (VPS) is an objective measure of visual ability. It is the reaction time (RT) needed to correctly search and/or reach for a visual stimulus. VPS depends on six main brain processing systems: auditory-cognitive, attentional, working memory, visuocognitive, visuomotor, and executive. We designed a new assessment methodology capable of activating these six systems and measuring RTs to determine the VPS of patients with HVFDs. METHODS: New software was designed for assessing subject visual stimulus search and reach times (S-RT and R-RT respectively), measured in seconds. Thirty-two different everyday visual stimuli were divided in four complexity groups that were presented along 8 radial visual field positions at three different eccentricities (10o, 20o, and 30o). Thus, for each HVFD and control subject, 96 S- and R-RT measures related to VPS were registered. Three additional variables were measured to gather objective data on the validity of the test: eye-hand coordination mistakes (ehcM), eye-hand coordination accuracy (ehcA), and degrees of head movement (dHM, measured by a head-tracker system). HVFD patients and healthy controls (30 each) matched by age and gender were included. Each subject was assessed in a single visit. VPS measurements for HFVD patients and control subjects were compared for the complete test, for each stimulus complexity group, and for each eccentricity. RESULTS: VPS was significantly slower (p < 0.0001) in the HVFD group for the complete test, each stimulus complexity group, and each eccentricity. For the complete test, the VPS of the HVFD patients was 73.0% slower than controls. They also had 335.6% more ehcMs, 41.3% worse ehcA, and 189.0% more dHMs than the controls. CONCLUSIONS: Measurement of VPS by this new assessment methodology could be an effective tool for objectively quantifying the visual ability of HVFD patients. Future research should evaluate the effectiveness of this novel method for measuring the impact that any specific neurovisual rehabilitation program has for these patients.

Assessment of macular ganglion cell loss patterns in neurologic lesions that mimic glaucoma.

PURPOSE: To evaluate patterns of macular retinal ganglion cell (RGC) loss measured by spectral domain optical coherence tomography in patients with neurologic lesions mimicking glaucoma. METHODS: We evaluated four patients with neurological lesions who showed characteristic patterns of RGC loss, as determined by ganglion cell thickness (GCT) mapping. RESULTS: Case 1 was a 30-year-old man who had been treated with glaucoma medication. A left homonymous vertical pattern of RGC loss was observed in his GCT map and a past brain magnetic resonance imaging (MRI) revealed a hemorrhagic lesion around the right optic radiation. Case 2 was a 72-year-old man with a pituitary adenoma who had a binasal vertical pattern of RGC loss that corresponded with bitemporal hemianopsia. Case 3 was a 77-year-old man treated for suspected glaucoma. His GCT map showed a right inferior quadratic pattern of loss, indicating a right superior homonymous quadranopsia in his visual field (VF). His brain MRI revealed a left posterior cerebral artery territory infarct. Case 4 was a 38-year-old woman with an unreliable VF who was referred for suspected glaucoma. Her GCT map revealed a left homonymous vertical pattern of RGC loss, which may have been related to a previous head trauma. CONCLUSIONS: Evaluation of the patterns of macular RGC loss may be helpful in the differential diagnosis of RGC-related diseases, including glaucoma and neurologic lesions. When a patient's VF is unavailable, this method may be an effective tool for diagnosing and monitoring transneuronal retrograde degeneration-related structural changes.

Comparison of the Behavioural Inattention Test and the Catherine Bergego Scale in assessment of hemispatial neglect.

The objective of the study was to correlate visual and behavioural assessments of hemispatial neglect caused by cerebrovascular accident. We assessed 17 consecutive right-hemisphere stroke patients with hemispatial neglect: the Catherine Bergego Scale (CBS) was used to evaluate neglect in spontaneous behaviour and the conventional subtests of the Behavioural Inattention Test (BIT C) were used to assess visual neglect. The proportional severity of both visual and behavioural neglect was calculated in each individual patient. Dissociations were found between mild neglect in visual screening tasks and moderate or severe neglect in behaviour, although in most patients, neglect was equally evident in both tests. Only the line bisection subtest from the BIT correlated significantly with the CBS, yet both tests showed good internal consistency. The line bisection test and several items of the CBS were especially sensitive in detecting the combination of visual field deficit and hemispatial neglect. In conclusion, we propose that visual fields should always be assessed in patients with neglect because neglect may be exacerbated by a visual field deficit and this can cause prolonged functional disability in everyday life situations. Specific rehabilitation methods might also be needed in neglect with or without hemianopia.

[Objective assessment of visual field defects using multifocal electroretinography]. / Objektivierung von Gesichtsfelddefekten mit Hilfe der multifokalen Elektroretinographie.

BACKGROUND: Multifocal electroretinography allows simultaneous recording of 61 focal electroretinographic signals from the retina of the posterior pole. The function of the outer retinal layers can be mapped for a visual field of 30.5 degrees radius. We herein describe the topography of such potentials in patients with hemianopic and concentric visual field defects. SUBJECTS AND METHODS: Six patients with visual field defects caused by chorioretinal and central visual pathways diseases were examined using multifocal ERG. RESULTS: In 30 normal volunteers in the entire 30 degrees visual field clear signals were obtained. In the patients with visual field defects caused by retinal diseases in areas with reduced light sensitivity diminished electroretinographical activity was found. In contrast, in patients with bitemporal hemianopsia due to a chiasmal lesion no correlation between visual field and magnitude of focal ERGs was seen. CONCLUSIONS: In retinal disorders defects in multifocal ERG presented the similar pattern as scotomata in perimetry. The patient with visual field defects due to disturbances in the chiasma exhibited a normal ERG-topography. In patients with visual field defects multifocal ERG supported differentiation of the location of the lesion.

Two techniques for the assessment of line bisection in visuo-spatial neglect: a single case study.

A patient with severe left neglect after surgery for basilar aneurysm is described. Her performance on freehand line bisection was compared and contrasted with the results from computerised visual display unit (VDU) presentation. In the latter format the patient makes her transections with a "mouse" controlled cursor arrow. The technique provides rigorous control over starting position and also allows self-corrections. Although left neglect persisted at longer line lengths under these conditions, the magnitude of the effect decreased significantly; the cross-over point where right displacements change to left displacements as a function of line length also varied between the three conditions (freehand, left and right computer-start).

The natural history of visual neglect after stroke. Indications from two methods of assessment.

A simple copying task and a measure of position preference on a multiple-choice test were used to assess the incidence of visual neglect after stroke. The patients studied were drawn from a register of strokes occurring in a typical health district. These tests detected visual neglect in 8-11% of patients 3 weeks after stroke and it was more frequent after right-sided rather than left-sided brain damage. Significant neglect was rarely observed by 6 months after stroke but further recovery did occur between 6 months and 1 year. Neglect appeared to exert a slowing influence on rehabilitation and we propose that training procedures to combat neglect should be evaluated for routine use in rehabilitation centres.

Screening for visual field abnormalities with automated perimetry.

Recent studies indicate that automated perimetry can serve as an effective method of screening for visual field abnormalities associated with ophthalmologic and neurologic disorders. The techniques have been successfully applied to the private practitioner's office for screening of patients and to mass visual field screening of the general population. This paper describes the principles underlying automated perimetric screening, evaluates the capabilities and limitations of such techniques, and provides some general guidelines for using automated perimetric screening procedures.

The assessment of 'vision for development' in severely visually handicapped babies.

Vision makes a substantial contribution to the pattern and rate of normal development. Considering infant development in 3 phases, global, integrative and specific the most important attributes to vision of development within each phase are discussed. A method for assessment of the aspects of vision most relevant to each child's current developmental needs is described and a philosophy outlined whereby the findings can be represented as a balanced practical prescription for development. The development of the visual system is often delayed in visually handicapped babies; some reasons are put forward and a concern that many may never achieve their potential maximum visual competence is expressed. A method for evaluating the current stage of visual development in a visually handicapped baby is described in which the findings form the starting point of a programme towards achieving maximum visual competence as young as possible.

Computerized localization of sources of evoked potentials in the assessment of visual field impairment.

Objective computer-based techniques are described along with their underlying theoretical rationale for investigating visual field disorders. The paper concerns methods for the collection and analysis of evoked potentials and provides a description of methods for obtaining information about the conduction pathways of the visual system for clinical, neurological and neuropsychological applications.

Assessment of visual field impairment by objective technique.

An objective psychophysical technique for investigating visual fields by averaged scalp potentials evoked by pattern gratings of alternating contrast and by sinusoidally modulated flicerking light is applied to a child with a right homonomous hemianopsia. This technique illustrates a value, in obtaining clinical data on visual fields in situations were subjective perimetry is difficult to administer or where conservating diagnostic methods do not yield evidence of pathology.