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Mechanisms Compensating for Visual Field Restriction in Adolescents With Eye (2012) 26, 1437–1445 & 2012 Macmillan Publishers Limited All rights reserved 0950-222X/12 www.nature.com/eye 1;2 3;4 1 Mechanisms L Jacobson , F Lennartsson , T Pansell ,GO¨ qvist CLINICAL STUDY Seimyr2 and L Martin2;5 compensating for visual field restriction in adolescents with damage to the retro-geniculate visual system 1Eye Unit, Department of Neuropaediatrics, Astrid Lindgren Children’s Hospital, Karolinska University Abstract Hospital, Stockholm, Background To describe visual field (VF) Conclusion Congenital and later-acquired Sweden outcome in three adolescents with damage to homonymous VF defects may, at least in 2 the optic radiation and to focus on young subjects, be compensated for by Department of Clinical Neuroscience, mechanisms that may compensate the scanning. Exotropia may compensate VF Ophthalmology and Vision, practical functional limitations of VF defects. defects and, therefore, the VF should be Karolinska Institutet, Design Descriptive, prospective multi-case tested before strabismus surgery. Stockholm, Sweden study in a hospital setting. Eye (2012) 26, 1437–1445; doi:10.1038/eye.2012.190; Participants Three teenagers with cerebral published online 21 September 2012 3Department of Medical visual dysfunction because of damage to the Physics, Karolinska University Hospital, retro-geniculate visual pathways. Keywords: VF defects; retro-geniculate visual Stockholm, Sweden Methods Best-corrected visual acuity and system; compensating mechanisms; eye alignment were assessed. Visual field adolescents 4Department of function was tested with Goldmann Neuroradiology, Karolinska perimetry, and with Rarebit, Humphrey University Hospital, Introduction Visual Field Analyzer and Esterman Stockholm, Sweden computerized techniques. Fixation was Brain damage has become the most common 5School of Health and registered with video oculography during cause of visual impairment in children in Welfare, Ma¨ lardalen 1–3 Rarebit examination. Magnetic resonance developed countries as a consequence of University, Eskilstuna, imaging of the brain illustrated brain damage improving survival of children with life- Sweden and its relation to the posterior visual threatening conditions with cerebral system. complications and of children born preterm. Correspondence: Results One of the three subjects had Assessment of visual function in these children Dr L Jacobson, Eye Unit, Department of bilateral asymmetric white matter damage of may be hampered by their inability to Neuropaediatrics, Astrid immaturity, early-onset exotropia, and a understand or to co-operate in the tests. Lindgren Children´ s relative homonymous VF defect, but normal Therefore, there is still limited information Hospital, Karolinska binocular VF. The second subject also had available of visual outcome, and in particular of University Hospital, bilateral asymmetric white matter damage of visual field (VF) function. Stockholm, SE 171 76, Sweden immaturity and showed an inferior right Brain imaging in children with cerebral visual Tel: +46 8 6683510 quadrantanopia, confirmed by the binocular impairment (CVI) reveals different pathologies E-mail: lena.jacobson@ field. Registration of fixation revealed of pre- or perinatal origin such as the following: karolinska.se or lena. automatic scanning during perimetry. The malformations, white matter damage of [email protected] third subject had an almost total left immaturity, and cortico-subcortical damage homonymous hemianopia after resection of a (focal infarct, multicystic encephalomalacia, Received: 9 May 2012 4 Accepted in revised form: brain tumour in the right temporal lobe. The basal ganglia, and thalamic lesions). When 20 July 2012 hemianopia could be compensated for by fast brain damage occurs at 24–34-week gestation, Published online: voluntary scanning. the lesions typically occur in the white matter. 21 September 2012 Compensating visual field mechanisms L Jacobson et al 1438 The specific lesions of the myelinated tracts comprise All subjects were examined with Goldmann perimetry intraventricular haemorrhage, periventricular and three different types of computerized perimetry. haemorrhagic infarction and periventricular Fixation and eye movements were registered during one leukomalacia.5 Each lesion may occur in isolation, but of the computerized perimetries. Best-corrected decimal more commonly any single infant may present with visual acuity was documented. Eye alignment was multiple lesions. When a child is examined with cerebral examined with cover test. Stereo acuity was tested with imaging in childhood, the periventricular white matter the TNO test (Lame´ris Ootech BV, Nieuwegein, The pathology may be visualized. However, at that time, it Netherlands),13 relying on the random-dot technique.14 may not be possible to know the cause. The end-stage The three boys and their parents gave consent before lesion is described as white matter damage of enrolment in the study. The study was approved by the immaturity, a common cause of CVI in prematurely born Regional Ethics Committee, Stockholm North, in children. Later-acquired lesions due to trauma, stroke, accordance with ethical standards on human tumour, or surgery may affect the posterior visual experimentation and with the Helsinki Declaration of pathways and cause visual impairment. This 1975, as revised in 1983. heterogeneity of aetiologies representing insults at different developmental stages, may explain different Perimetry prerequisites for reorganization and compensation, reflected in the VF outcome. Kinetic manual Goldmann perimetry was performed in a Exotropia as compensation in homonymous standardized way.15 The extent of the VF was determined hemianopia has been suggested.6,7 Another using the II/4e stimulus. For the central VF, one or more compensatory mechanism based on saccadic exploration of the stimuli I/3e, I/2, I/1e and, if possible, 0/1e were towards the blind field has been described.8 Motion used. The fixation and co-operation during VF detection in the blind field has also been described in examinations of each subject were continuously carefully adults with acquired hemianopia.9,10 With such monitored and encouraged by the examiner. Every compensation mechanisms, we can expect that the subject was prompted to fixate in the middle of the practical binocular VF function in everyday living differs fixation mark, and every attempt to shift gaze led to from the monocular VF function assessed under strict renewed calls for looking straight ahead at the fixation control of fixation. mark. None of them had any obvious problems with Training programs have been developed for adults shifting attention. with previously normal VF function who have acquired For quantitative measurement of the central VF, the homonymous hemianopia, most often after stroke. These Rarebit Perimetry was used, testing the 301 Â 201 central rehabilitation techniques are based on optical devices, on VF. The Rarebit perimetry technique16 tests the integrity eye-movement training or visual restitution training.11 of the retinal receptor matrix, using very small and bright The value of such training programs is debated.12 No dots against a dark background and has shown to be training programs have yet been designed for children sensitive for damage in the visual system of different with congenital or very early-acquired VF defects. origins.16–19 The task for the subject is to follow a The practical consequences of VF defects in children flickering fixation mark that moves over the computer with pre- and perinatal brain damage for mobility and screen and to indicate perception of the dots by a single- orientation, for everyday life, for reading and for future or a double-click on the computer mouse. Fixation driving, have not yet been thoroughly described. stability is supervised by the examiner and encouraged The purpose of this multiple case presentation is to by dynamically changing the fixation mark, ie, the suggest possible automatically developed compensatory fixation mark gradually diminishes in size, signalling a mechanisms that improve VF function in children with pending presentation. In order to cover a larger VF area, lesions affecting the posterior visual pathways because of the fixation mark is moved according to a predefined pre- and perinatal or later-acquired brain damage. pattern during the examination. The results are expressed as the mean hit rate, ie, the percentage of stimulus presented. Normal hit rates for adults have Subjects and methods been found to range from 93 to 100% (median 96%),16,18 Three teenagers with cerebral visual dysfunction because and are approximately the same for young subjects with of the damage to the retro-geniculate visual pathways a median mean hit rate of 93% (range 78–100) in 6.5–12- were recruited. Two had spastic cerebral palsy due to year-old subjects and 97% (range 89–100) in 14–20-year- white matter damage of immaturity. One subject had old subjects.20 The results are also presented graphically, undergone surgery for a brain tumour affecting the optic where unfilled rectangles indicate that all stimuli have radiation in the temporal lobe. been perceived in that area; the darker the rectangle, Eye Compensating visual field mechanisms L Jacobson et al 1439 the more the stimuli that have been missed (see Figure 3). and a mixture of horizontal and vertical saccades The learning effect is reported to be very low, o1% unit (amplitude 6.1 deg SD 3.5) with no preferred direction. in young subjects.21 The monocular VF examinations were performed with
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