F. Groenendaal

Visual field and grating acuity development in low-risk preterm infants during the first 2 1/2 years after term

The effect of early visual experience on visual field size and grating acuity development was studied longitudinally in 36 appropriate for gestational age (AGA) and 26 small for gestational age (SGA) low-risk preterm infants. These were selected out of 194 very low birth weight (VLBW) infants (birthweight less than 1500 g) born in 1985 and 1986. Criteria for inclusion as low-risk were the absence of neurological, respiratory, circulatory and alimentary problems in the neonatal period; no retinopathy of prematurity and no evidence of abnormality on the neonatal cranial ultrasound scans. Binocular field sizes were assessed using kinetic arc perimetry. Binocular grating acuity was tested by means of the prototype version of the acuity card procedure. Results were compared with norms obtained in control fullterms in earlier studies. Infants were tested at 6 weeks, 6, 6, 9 and 12 months of age from the expected term date. Twenty-two of these infants were retested at 2 1/2 years of corrected age. Visual field size and visual acuity estimates of (both AGA and SGA) low-risk, VLBW preterms and control fullterms overlapped at all test ages, except for a slight but significantly faster development of the upper and the lower visual field at 6 weeks corrected age in the preterm group. These results indicate that for clinical purposes visual experience before the expected term date has not only no measurable effect on the normal development of behavioural acuity, but also no accelerating effect on the development of peripheral vision.

Effects of perinatal hypoxia on visual development during the first year of (corrected) age

Visual development was assessed in 124 infants (112 preterms and 12 fullterms) who had suffered from perinatal hypoxia and in 55 control preterm infants during the first year of corrected age. Using behavioural techniques, visual functions were tested during follow-up visits in the Sophia Childrens Hospital. Corrected ages at testing ranged from 3 months to 1 year. During this period, infants with perinatal hypoxia showed more abnormalities in visual functions than preterm control infants. Gestational age at birth did not influence the outcome of visual development after perinatal hypoxia. Most visual impairments were demonstrated at 3 and 6 months of age. All infants with severe neuro-developmental handicaps showed visual deficits, although neuro-developmental abnormalities and visual deficits could be present as isolated phenomena. Ultrasound abnormalities related well with visual dysfunctions. Prospective studies of infants with visual deficits and a history of perinatal hypoxia are indicated.

51 THE PREDICTIVE VALUE OF ABNORMAL NEUROLOGICAL DEVELOP MENT AT 6 WEEKS OF CORRECTED AGE |[lpar]|CA|[rpar]| FOR ABNORMAL VISUAL FUNCTIONS AT 1 YEAR IN VERY LOW BIRTH WEIGHT |[lpar]|VLBW|[rpar]| INFANTS

Early neurological examination has generally been considered of limited value in predicting developmental outcome. A high incidence of abnormal visual functions has been reported in VLBW infants. We studied the predictive value of early neurological examination for the development of visual functions in 56 VLBW infants, gest.age 24.8-35.0 w (median 30.6), bwt 690-1490 g (median 1115). Neurological assessment (Prechtl) was performed at 6 weeks CA. Visual acuity (acuity cards), visual field (kinetic perimetry) and optokinetic nystagmus were assessed binocularly at 1 year CA. Visual functions were normal in 40 out of 47 neurologically optimal and suboptimal infants, while 6 out of the 9 neurologically abnormal infants showed abnormal visual functions (p<0.005 Fisher exact). Conclusion: 1. VLBW infants are at risk for abnormal development of visual functions. 2. The incidence of abnormal visual functions is high in infants with abnormal neurology at 6 weeks. However, normal neurology at 6 weeks does not exclude abnormal visual functions at 1 year of age.

VISUAL ACUITY IN VERY LOW BIRTH WEIGHT INFANTS AT 6 WEEKS OF (CORRECTED) AGE

We studied the effect of early visual experience on the development of visual acuity (VA) in preterm infants. We assessed VA using the acuity card method in 63 very low birth weight (VLBW) infants, bwt 700-1495g (1150±240;X±SD), gest. age 25.8-35.0 wks (30.2±4.3). VA was assessed at 11.3-20.3 wks postnatal age (pa) (15.8±2.2), corresponding with 2.1-9.1 wks corrected age (ca) (6.0±1.3). Funduscopy was normal in all infants. The results were compared with those obtained in fullterm low risk infants at the age of 6.8 and 15.9 wks:*: min. of arc ± octaves (17.7 min. of arcx6/106 Snellen equiv.) The results show that visual acuity assessed with the acuity card procedure is significant lower (p<0.01. Students t-test) in VLBW infants in comparison with low risk infants of the same postnatal age, but is not different when age is corrected for prematurity. The present results fail to demonstrate an acceleration of acuity development by early visual stimulation.

PERINATAL HYPOXIA AND VISUAL FUNCTIONS IN VERY LOW BIRTH WEIGHT INFANTS AT 6 WEEKS OF (CORRECTED) AGE

A prospective study was started to determine the effects of perinatal hypoxic events on visual development in a group VLBW infants (n=113), born between 8/1/85 and 7/31/86. Binocular visual functions were assessed in 71 out of 93 survivors. Infants with RLF were excluded. In the hypoxic group (n=44) gest.age ranged from 24.8 to 35.0 wks (29.1±5.0,-X±SD), bwt from 690 to 1495g (1120±260); in the non-hypoxic group (n=27) gest.age ranged from 28.6 to 34.3 wks (30.6±6.1), bwt from 700 to 1495 g (1145±300). Visual acuity, visual field size and optokinetic nystagmus were assessed at 8.4 to 23.0 wks of age (6.0 wks corrected age). Visual acuity with the acuity card method was significantly lower in the hypoxic group (23 min. of arc ± 0.84 octaves) than in the non-hypoxic group (17±0.47) (p<0.05. Students t-test). Optokinetic nystagmus was asymmetric in 13 hypoxic infants and in 3 non-hypoxic infants (p<0.05, x2-test). No difference was found in visual field size. The data indicate that perinatal hypoxic events are associated with a higher incidence of visual impairment in VLBW infants at 6 weeks of corrected age. Further studies are needed regarding the effects on visual functions at later age.