Binasal hemianopia in two sisters.

Binasal hemianopia is a rare visual field defect. A teenage girl presented with blurred vision and persistent headaches following a minor head injury. The ocular examination was normal except for a binasal hemianopia, and subsequent neuroimaging was also unremarkable. Her older sister was found to have the same visual field defect, also with normal neuroimaging. This represents the first reported case of binasal hemianopia found in siblings. Given that no neurological or ocular cause was identified in either sister, this supports the theory of an unknown congenital aetiology.

Blindsight in children with congenital and acquired cerebral lesions.

It has been shown that unconscious visual function can survive lesions to optical radiations and/or primary visual cortex (V1), a phenomenon termed "blindsight". Studies on animal models (cat and monkey) show that the age when the lesion occurs determines the extent of residual visual capacities. Much less is known about the functional and underlying neuronal repercussions of early cortical damage in humans. We measured sensitivity to several visual tasks in four children with congenital unilateral brain lesions that severely affected optic radiations, and in another group of three children with similar lesions, acquired in childhood. In two of the congenital patients, we measured blood oxygenation level dependent (BOLD) activity in response to stimulation of each visual field quadrants. Results show clear evidence of residual unconscious processing of position, orientation and motion of visual stimuli displayed in the scotoma of congenitally lesioned children, but not in the children with acquired lesions. The calcarine cortical BOLD responses were abnormally elicited by stimulation of the ipsilateral visual field and in the scotoma region, demonstrating a profound neuronal reorganization. In conclusion, our data suggest that congenital lesions can trigger massive reorganization of the visual system to alleviate functional effects of early brain insults.

Torsional anomalous retinal correspondence effectively expands the visual field in hemianopia.

PURPOSE: Exotropia in congenital homonymous hemianopia has been reported to provide field expansion that is more useful when accompanied with harmonious anomalous retinal correspondence (HARC). Torsional strabismus with HARC provides a similar functional advantage. In a subject with hemianopia demonstrating a field expansion consistent with torsion, we documented torsional strabismus and torsional HARC. METHODS: Monocular visual fields under binocular fixation conditions were plotted using a custom dichoptic visual field perimeter. The dichoptic visual field was also modified to measure perceived visual directions under dissociated and associated conditions across the central 50° diameter field. The field expansion and retinal correspondence of a subject with torsional strabismus (along with exotropia and right hypertropia) with congenital homonymous hemianopia was compared with that of another exotropic subject with acquired homonymous hemianopia without torsion and to a control subject with minimal phoria. Torsional rotations of the eyes were calculated from fundus photographs and perimetry. RESULTS: Torsional anomalous retinal correspondence documented in the subject with congenital homonymous hemianopia provided a functional binocular field expansion up to 18°. Normal retinal correspondence was mapped for the full 50° visual field in the control subject and for the seeing field of the acquired homonymous hemianopia subject, limiting the functional field expansion benefit. CONCLUSIONS: Torsional strabismus with anomalous retinal correspondence, when occurring with homonymous hemianopia provides useful field expansion in the lower and upper fields. Dichoptic perimetry permits documentation of ocular alignment (lateral, vertical, and torsional) and perceived visual direction under binocular and monocular viewing conditions. Evaluating patients with congenital or early strabismus for HARC is useful when considering surgical correction, particularly in the presence of congenital homonymous hemianopia.

Congenital homonymous hemianopia and cortical migration abnormalities in a young adult.

Congenital homonymous hemianopia isan uncommon entity usually diagnosed in early adulthood, with the patient having no prior knowledge of a visual field defect. The authors describe an 18-year-old woman with asymptomatic congenital homonymous hemianopia and an unusual constellation of associated intracranial abnormalities.

Optical coherence tomography (OCT) findings in congenital/long-standing homonymous hemianopia.

PURPOSE: To report abnormalities of retinal nerve fiber layer (RNFL) thickness using optical coherence tomography (OCT) in patients with trans-synaptic degeneration. DESIGN: Observational case reports. METHODS: Two patients with congenital/long standing occipital lobe lesions who had asymptomatic homonymous hemianopic field defects were examined using OCT. RESULTS: In case 1, there was loss of RNFL in the projection of the nasal hemifovea temporally and the horizontal projection nasally in the right eye and thinning in the superior and inferior temporal arcades in the left eye corresponding to visual field abnormalities. In case 2, abnormalities in the RNFL pattern corresponded to the visual defects even though the field defect was incomplete. CONCLUSION: OCT measurements of the RNFL provide useful information in the diagnosis of congenital/long standing occipital lobe lesions.

Effects of left parietal injury on covert orienting of attention.

OBJECTIVE: To assess the effects of left parietal injury on covert visual attention during a detection task and a pointing task. METHODS: The Posner's paradigm was given to a patient who was found at the age of 74 to have spent all his life without the left parietal lobe as a result of a congenital perinatal insult and to a control subject. In one session subjects were required to provide an arbitrary response at stimulus appearance (key press). In another session subjects were required to point to the stimulus. RESULTS: The patient was able to disengage covert attention from a cued position when the task was to provide an arbitrary key press response in a similar fashion to a control subject with no neurological deficits. By contrast, he was impaired in disengaging attention from a cued position when the task was to reprogramme an overt pointing action. CONCLUSIONS: Response to cued information is differentially available depending on task. It is suggested that mechanisms concerned with the attention for action systems are located within the left parietal lobe.

Congenital optic tract syndrome: magnetic resonance imaging and scanning laser ophthalmoscopy findings.

Lesions of the optic tract produce a distinctive pattern of optic atrophy and visual field loss and may be due to either congenital or acquired causes. We report a case of a congenital optic tract syndrome and correlate the magnetic resonance imaging findings with the appearance of nerve fiber layer defects found by confocal scanning laser ophthalmoscopy.

[Surgical and botulinum toxin treatment in two cases of abnormal retinal correspondence-exotropia with congenital homonymous hemianopsia].

We report 2 unusual cases of congenital occipital hemianopsia associated with abnormal retinal correspondence (ARC)-exotropia. Two Japanese males, 25 and 28 years of age, visited our hospital for surgical correction of manifest exotropia with dissociated vertical deviation and overaction of the superior oblique muscle. Visual field examination demonstrated homonymous hemianopsia with approximately 5 to 10 degrees of macular sparing. Visually evoked potential examination showed small amplitude similar to dissociated vertical deviation patients in all half-field stimulation. Electrooculogram examination demonstrated defective pursuit to the ipsilateral side. Some investigators have speculated that progressive exotropia compensates for homonymous hemianopsia and is a rare contraindication for strabismus surgery. To confirm the deterioration of motor and visual functions before surgery in these patients, we tried injections of botulinum A type toxin into the lateral rectus muscle ipsilateral to the hemianopsia. Contrary to the hypothesis, our patients had no change in their binocular visual fields and visual function. Finally, we performed recession of the lateral rectus muscle, so that both patients were satisfied with their ocular alignment, with no marked change of visual behavior.

Isolated congenital hemianopia caused by prenatal injury to the optic radiation.

Isolated congenital hemianopias are typically caused by developmental abnormalities of the occipital lobe cortex. We describe two patients with an incidental partial hemianopia associated with unilateral periventricular leukomalacia that was acquired prenatally. Magnetic resonance imaging scans suggest a late second or early third trimester unilateral cerebral ischemic event.

Neuro-imaging and positron emission tomography of congenital homonymous hemianopsia.

Congenital homonymous hemianopsia is an uncommon asymptomatic visual field defect discovered typically in young adult life that is caused by a diverse group of insults to the retrochiasmal afferent visual system occurring prenatally, at birth, or during early childhood. We treated eight patients with congenital homonymous hemianopsia; seven with damage involving the optic radiations and one with an abnormality of the optic tract. We performed positron emission tomography using 18F-fluoro-2-deoxyglucose on two patients with dense homonymous hemianopsias, lesions of the contralateral optic radiations, and largely intact occipital cortex. These studies showed minimal abnormalities in resting visual cortex glucose metabolism of the affected visual cortex.

Detection of isolated occipital lobe anomalies during early childhood.

The authors report two children with isolated occipital lobe anomalies detected by visual evoked potentials (VEPs) and confirmed by MRI and CT scanning. Both had a markedly asymmetrical occipital distribution of flash and pattern VEPs. One child had acuity reduced to 6/36, and testing on confrontation suggested an homonymous hemianopia. The second child was visually inattentive to one side during infancy. Neither child had band atrophy of the optic disc or an afferent pupillary defect. Isolated abnormalities of the occipital lobes are difficult to detect by clinical examination during infancy and early childhood. Recording VEPs from a horizontal array of occipital electrodes can be helpful in detecting subtle occipital lobe abnormalities.

Occipital lobe dysplasia. Magnetic resonance findings in two cases of isolated congenital hemianopia.

Magnetic resonance images were obtained from two patients with isolated congenital hemianopia. Computed tomographic investigations failed to show occipital abnormalities commensurate with the field defects. Magnetic resonance imaging identified dysplasia imaging of the striate cortex and underlying white matter.

Eye-head coordination in homonymous hemianopia.

Quantitative studies of latencies and trajectories of eye-head movements during visual search and fixation in patients with occipital hemianopia show that (1) the latency of head movement is bilaterally increased, with significantly greater delays in movements toward the blind side; (2) the compensatory eye movements (CEMs) during head movements toward the blind side have increased velocity; (3) these CEMs entail a non-vestibular anticipatory component; and (4) head movements toward the blind side are comprised of multiple steps similar to staircase eye movements documented in previous studies. Hemianopic patients seemingly simplify search and fixation strategies by minimizing or entirely eliminating head movements and relying on eye movements instead.