Visual dysfunction and ocular signs associated with periventricular leukomalicia in children born preterm
Abstract: The immature visual system is vulnerable to adverse events in infants born preterm. Both retinopathy of prematurity and periventricular leukornalacia may affect visual function and ocular appearance. The aims of the study were to investigate the prevalence of brain lesions in visually impaired children born preterm, to find associations between the brain lesion and ocular findings, to characterise the pattern of visual dysfunction in periventricular leukomalacia and to find clinical and educational applications. Paper I describes a population-based group of 27 children born 1980-1990, blind because of bilateral retinopathy of prematurity stage 5. Nineteen of 27 children exhibited evidence of brain lesion. In Paper II visual, cognitive and motor function was assessed in 13 children with visual impairment due to periventricular leukornalacia confirmed with computed tomography or magnetic resonance imaging of the brain. The pattern of visual dysfunction was characterised by crowding, visual field defects, visuo-spatial deficits but well developed colour vision. Seven of 13 children had cerebral palsy. In Paper III digital image analysis of fundus photographs was performed in 17 children with periventricular leukomalacia and in 17 controls. We found larger cupping of normal- sized optic discs in the study group, maybe as a result of transsynaptic degeneration caused by the primary lesion of the optic radiation during a sensitive period in the immature brain. In Paper IV fixation and ocular motor function were recorded with the Ober-2 infrared reflection technique in 19 children with periventricular leukornalacia. Sixteen of 19 had nystagmus and 18 of 19 had strabismus. Paper V describes the causes of visual impairment in a population-based group of visually impaired children in V rmland born preterm 1989-1995. Sixteen of 18 children had cerebral lesions as the cause of visual impairment and ten of these had periventricular leukomalacia. These ten children represent 15% of all and 65% of preterm born visually impaired children. No child had retinopathy of prematurity as the cause of visual impairment. In Paper VI visual and cognitive development, ocular motor function and its effects on reading were studied in four children with visual impairment due to periventricular leukomalacia. We found a delayed and limited maturation of visual acuity, visual fields and an inability to perform normal reading eye movements. Visuo-spatial ability seemed to play a critical part in reading achievement. The major conclusions of this thesis are that brain lesion is common in visually impaired children born preterm. Magnetic resonance imaging is the method of choice for diagnosing the lesion. Visuo-ocular dysfunction in periventricular leukomalacia is characterised by crowding, visual field defects, strabismus, nystagmus, eye movement disorders and large cupping of the optic disc. Children with mild periventricular leukomalacia may present as only strabismic. Habilitation and education need to be adapted.
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