Mechanisms compensating for visual field restriction in adolescents with damage to the retro-geniculate visual system

Abstract

Background To describe visual field (VF) outcome in three adolescents with damage to the optic radiation and to focus on mechanisms that may compensate the practical functional limitations of VF defects. Design Descriptive, prospective multi-case study in a hospital setting. Participants Three teenagers with cerebral visual dysfunction because of damage to the retro-geniculate visual pathways. Methods Best-corrected visual acuity and eye alignment were assessed. Visual field function was tested with Goldmann perimetry, and with Rarebit, Humphrey Visual Field Analyzer and Esterman computerized techniques. Fixation was registered with video oculography during Rarebit examination. Magnetic resonance imaging of the brain illustrated brain damage and its relation to the posterior visual system. Results One of the three subjects had bilateral asymmetric white matter damage of immaturity, early-onset exotropia, and a relative homonymous VF defect, but normal binocular VF. The second subject also had bilateral asymmetric white matter damage of immaturity and showed an inferior right quadrantanopia, confirmed by the binocular field. Registration of fixation revealed automatic scanning during perimetry. The third subject had an almost total left homonymous hemianopia after resection of a brain tumour in the right temporal lobe. The hemianopia could be compensated for by fast voluntary scanning.

Visual function and compensatory mechanisms for hemianopia after hemispherectomy in children

“…This phenomenon was first reported by Herzau et al., who described two adult patients with HH and XT, both existing from early childhood, that led to functional enlargement of the binocular visual field, an observation later confirmed by Saleh et al . and Jacobson et al . In our study, the postoperative shift of ocular alignment to contralateral XT advocates a compensatory origin.…”

“…We speculate that these children somehow prefer the expansion of the functional visual field by means of contralateral XT above normal ocular alignment. In addition, several authors have suggested that the expected double vision might be avoided when this functional visual field enlargement by XT is accompanied by an anomalous retinal correspondence, resulting in continuous XT, or by using scanning movements into the blind field, observed as intermittent XT . Both continuous and intermittent were observed in our hemispherectomized children.…”

“…Equally intriguing is the observation that 17 (38%) of 45 hemispherectomized children develop contralateral XT . This phenomenon was first reported by Herzau et al., who described two adult patients with HH and XT, both existing from early childhood, that led to functional enlargement of the binocular visual field, an observation later confirmed by Saleh et al .…”

“…8 Some children seem to develop coping strategies to maximize the functional visual field. Several case reports and case series have demonstrated that an anomalous head posture (AHP) [9][10][11][12][13] and exotropia (XT) 10,12,[14][15][16][17][18][19] contralateral to the side of brain damage may compensate a hemianopic defect in children and adults with early onset HH. XT contralateral to the brain damage, that is, toward the hemianopic side, may create a more panoramic view and broaden the functional visual field.…”

Cerebral Visual Impairment in Children

“…Consequently, they had no (or only mild) diffi culties in everyday life activities, at least no more 'diffi culties' than children of the same age may also have. Numbers in brackets refer to bilateral visual fi eld impairment N number of subjects, UNI, BIL uni-and bilateral visual fi eld loss It is possible that in some cases, the development of divergent strabismus develops and becomes compensatory for the hemianopia, and care has to be taken when considering cosmetic strabismus surgery (Jacobson et al 2012 ). In the context of neurological and neuroradiological examinations of an 11-year-old girl with suspected epilepsy, a small cystic lesion was detected in the left occipital lobe.…”