L K Jacobson¹, O Flodmark², L Martin3
¹Institute for Special Needs Education, Vision Resource Centre, Stockholm, Sweden; ²Karolinska University Hospital, Department of Neuroradiology, Stockholm, Sweden; 3Karolinska Institute, St Eriks Eye Hospital, Stockholm, Sweden
Background: Brain damage of pre- and perinatal origin, affecting the visual pathways, accounts for an increasing group of visually impaired children. This multiple-case study aims to describe different patterns of visual function in children with cerebral visual impairment and its relation to the time of insult.
Method: Visual acuity and visual fields were assessed in four children with cerebral visual impairment. Their brain lesion was documented with computed tomography or magnetic resonance imaging. The time of insult was estimated from the clinical history and from the appearance of the cerebral imaging.
Result: One girl with a unilateral brain malformation affecting the white matter, did not have any hemianopia but very low visual acuity, whereas another girl with a unilateral brain lesion caused by a haemorrhage at birth at full term had a homonymic hemianopia and well developed visual acuity. Two prematurely born children with bilateral periventricular white matter damage were assessed. A lesion from gestational age 28 weeks resulted in normal outer limits of the fields associated with low visual acuity whereas a lesion from gestational week 33 caused bilateral inferior visual field restriction in combination with normal visual acuity.
Conclusion: Lesions to the immature brain interrupting axons in the posterior visual pathways affect visual function. We speculate that the surviving neurons after an insult to the very immature brain may cover the peripheral field at the expense of visual acuity whereas insults to the posterior visual system occurring near or at term may result in a more "adult"-like pattern of functional deficit with visual field restriction in combination with better developed visual acuity. Thus not only the location and extension of a brain lesion but also the time at which it occured is of importance for visual outcome.
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