Visual Impairment in Finnish Children : Prevalence, causes and morbidity of full-term and preterm children with visual impairment born from 1972 through 1989

The prevalence and the causes of childhood visual impairment in Finland during the 1970s and the 1980s were investigated, with special attention to risk factors and further prevention of visual impairment in children. The primary data on children with visual impairment were obtained from the Finnish Register of Visual Impairment, one of the patient registers kept up by the National Research and Development Centre for Welfare and Health (Stakes). The data were supplemented from other registers in Stakes and from patient records of the children in Finnish central hospitals. Visual impairment had been registered in 556 children from a population of 1,138,326 children between ages 0-17, born from 1972 through 1989. The age-specific prevalence of registered visual impairment was 49/100,000 in total. Of them, 23/100,000 were blind children and 11/100,000 were children born prematurely. Boys were impaired more often and more severely than girls. Congenital malformations (52%), systemic diseases (48%), and multiple impairments (50%) were common. The main ophthalmic groups of visual impairment were retinal diseases (35%), ocular malformations (29%), and neuro-ophthalmological disorders (29%). Optic nerve atrophy was the most common diagnosis of visual impairment (22%), followed by congenital cataract (11%), retinopathy of prematurity (10%), and cerebral visual impairment (8%). Genetic factors (42%) were the most common etiologies of visual impairment, followed by prenatal (30%) and perinatal (21%) factors. The highest rates of blindness were seen in cerebral visual impairment (83%) and retinopathy of prematurity (82%). Retinopathy of prematurity had developed in the children born at a gestational age of 32 weeks or earlier. Significant risks for visual impairment were found in the association with preterm births, prenatal infections, birth asphyxia, neonatal respiratory difficulties, mechanical ventilation lasting over two weeks, and hyperbilirubinemia. A rise in blind and multi-impaired children was seen during the study period, associating with increases in the survival of preterm infants with extremely low birth weight. The incidence of visual impairment in children born prematurely was seven times higher than in children born at full term. A reliable profile of childhood visual impairment was obtained. The importance of highly qualified antenatal, neonatal, and ophthalmological care was clearly proved. The risks associated with pre- and perinatal disorders during pregnancy must be emphasized, e.g. the risks associated with maternal infections and the use of tobacco, alcohol, and drugs during pregnancy. Obvious needs for gene therapies and other new treatments for hereditary diseases were also proved.

The Effect of Intrauterine Growth Restriction on Long-Term Outcome in Very or Extremely Low Birth Weight Infants

The project consisted of two long-term follow-up studies of preterm children addressing the question whether intrauterine growth restriction affects the outcome. Assessment at 5 years of age of 203 children with a birth weight less than 1000 g born in Finland in 1996-1997 showed that 9% of the children had cognitive impairment, 14% cerebral palsy, and 4% needed a hearing aid. The intelligence quotient was lower (p<0.05) than the reference value. Thus, 20% exhibited major, 19% minor disabilities, and 61% had no functional abnormalities. Being small for gestational age (SGA) was associated with sub-optimal growth later. In children born before 27 gestational weeks, the SGA had more neuropsychological disabilities than those appropriate for gestational age (AGA). In another cohort with birth weight less than 1500 g assessed at 5 years of age, echocardiography showed a thickened interventricular septum and a decreased left ventricular end-diastolic diameter in both SGA and AGA born children. They also had a higher systolic blood pressure than the reference. Laser-Doppler flowmetry showed different endothelium-dependent and -independent vasodilation responses in the AGA children compared to those of the controls. SGA was not associated with cardio-vascular abnormalities. Auditory event-related potentials (AERPs) were recorded using an oddball paradigm with frequency deviants (standard tone 500 Hz and deviant 750-Hz with 10% probability). At term, the P350 was smaller in SGA and AGA infants than in controls. At 12 months, the automatic change detection peak (mismatch negativity, MMN) was observed in the controls. However, the pre-term infants had a difference positivity that correlated with their neurodevelopment scores. At 5 years of age, the P1-deflection, which reflects primary auditory processing, was smaller, and the MMN larger in the preterm than in the control children. Even with a challenging paradigm or a distraction paradigm, P1 was smaller in the preterm than in the control children. The SGA and AGA children showed similar AERP responses. Prematurity is a major risk factor for abnormal brain development. Preterm children showed signs of cardiovascular abnormality suggesting that prematurity per se may carry a risk for later morbidity. The small positive amplitudes in AERPs suggest persisting altered auditory processing in the preterm in-fants.