S Anker

Two infant vision screening programmes: prediction and prevention of strabismus and amblyopia from photo- and videorefractive screening.

Two infant vision screening programmes on total populations in the Cambridge Health District have been designed to identify manifest strabismus and strabismogenic and amblyogenic refractive errors at 7–9 months of age. The first, completed, programme used the isotropic photorefractor with cycloplegia together with a standard orthoptic examination. The second, current, programme uses the VRP-1 isotropic videorefractor to identify infants with accommodative lags which are followed up by refraction under cycloplegia. Both programmes show good agreement between infants identified at screening and retinoscopic refractions at follow-up, showing that photo- and videorefraction (with or without cycloplegia) can be effective methods for screening for ametropia in infants and young children. In each programme 5–6% of infants showed abnormal levels of hyperopia (≥3.5 D in any meridian), less than 1% showed anisometropia ≥1.5 D; very few infants (0.25%) showed −3 D myopia or greater. Less than 1% showed manifest strabismus. Hyperopic and anisometropic children entered a randomised controlled trial of partial refractive correction. All children identified at screening, alongside appropriate control groups, are extensively followed up to age 4 years. The first programme has found that children who were hyperopic in infancy were 13 times more likely to become strabismic, and 6 times more likely to show measurable acuity deficits by 4 years, compared with controls. Wearing a partial spectacle correction reduced these risk ratios to 4:1 and 2.5:1 respectively. The impaired acuity can be attributed, in part, to meridional amblyopia resulting from persisting astigmatism. Both hyperopic and myopic infants showed refractive changes in the direction of emmetropia between 9 months and 4 years. Wearing a partial spectacle correction did not affect this process of emmetropisation, but does provide the possibility of reducing the incidence of common pre-school vision problems.

Infant emmetropization: longitudinal changes in refraction components from nine to twenty months of age.

Rapid emmetropization is described in pediatrically normal infants from 9 months of age during the following year. The infants, obtained from various categories of the Cambridge population screening program, provided a broad range of refractive errors. The large group of 254 nonanisometropic infants studied allowed the mean rate of change and dependence on the initial refraction value to be determined. Refraction was measured by cycloplegic retinoscopy. Rapid emmetropization changes occurred in the following refractive components: mean spherical equivalent (MSE), astigmatism magnitude, the horizontal astigmatism component, the infants most positive meridian, and the infants most negative meridian. The MSE and astigmatism rates of change (diopters/year), were highly dependent on their respective initial powers (r=—0.61 and r=—0.76). The percentage weighted mean proportional rate of change for MSE was - 30% (SE 4%) and for astigmatism magnitude it was - 59% (SE 14%). There was much individual variation, with some exhibiting fast emmetropization and others not. The MSE and astigmatism changes, however, were almost independent of each other. The refractive errors of the most positive and most negative meridians emmetropize because they are both derived from the MSE and half the astigmatism. With-the-rule astigmatism was more prevalent than against-the-rule astigmatism at 9 months of age, and with-the-rule astigmatism exhibited a significantly greater proportional rate of change. The relationship of emmetropization and refractive screening is considered. A new component “MOMS” is introduced, the maximum ocular meridional separation when both eyes are considered. Thus incorporating astigmatism and anisometropia may be a good single indicator of conditions associated with later amblyopia. The almost independent emmetropization of the MSE and astigmatism components is an important result to consider in theories of emmetropization, refractive screening, clinical prescribing, and the evaluation of infants in treatment trials.

Development of Orientation Discrimination in Infancy

It has previously been found by us, with a visual evoked potential (VEP) measure, that orientation discrimination of dynamic patterns in infants can be demonstrated from around 6 weeks after birth. Experiments are reported in which orientation discrimination was measured behaviourally, in two infant control habituation procedures, with both dynamic and static patterns. When dynamic patterns identical to those in our previous VEP studies were used, the first positive evidence of orientation discrimination was found at around 6 weeks postnatally. The time course of both the VEP and the behavioural measures was similar. However, with static patterns, evidence of orientation discrimination by newborns was found if the infants were allowed to compare the habituated and novel orientations in a paired simultaneous comparison after habituation, but was not found when the habituated and novel stimulus were presented sequentially. The positive evidence of orientation discrimination in newborns supports the hypothesis that some form of orientationally tuned detectors can be used for discrimination of static patterns at birth. However, some developmental change over several weeks seems to be required before a positive electrophysiological VEP response can be measured for dynamic patterns changing in orientation.

Infant Hyperopia: Detection, Distribution, Changes and Correlates—Outcomes From the Cambridge Infant Screening Programs

Purpose. To report on two population screening programs designed to detect significant refractive errors in 8308 8- to 9-month-old infants, examine the sequelae of infant hyperopia, and test whether early partial spectacle correction improved visual outcome (strabismus and acuity). The second program also examined whether infant hyperopia was associated with developmental differences across various domains such as language, cognition, attention, and visuomotor competences up to age 7 years. Linked programs in six European countries assessed costs of infant refractive screening. Method. In the first program, screening included an orthoptic examination and isotropic photorefraction, with cycloplegia. In the second program we carried out the same screening procedure without cycloplegia. Hyperopic infants (≥+4 D) were followed up alongside an emmetropic control group, with visual and developmental measures up to age 7 years, and entered a controlled trial of partial spectacle correction. Results. The second program showed that accommodative lag during photorefraction with a target at 75 cm (focus ≥+1.5 D) was a marker for significant hyperopia. In each program, prevalence of significant hyperopia at 9 to 11 months was around 5%; manifest strabismus was 0.3% at 9 months and 1.5 to 2.0% by school age. Infant hyperopia was associated with increased strabismus and poor acuity at 4 years. Spectacle wear by infant hyperopes produced better visual outcome than in uncorrected infants, although an improvement in strabismus was found in the first program only. The corrections did not affect emmetropization to 3.5 years; however, both corrected and uncorrected groups remained more hyperopic than controls in the preschool years. The hyperopic group showed poorer overall performance than controls between 1 and 7 years on visuoperceptual, cognitive, motor, and attention tests, but showed no consistent differences in early language or phonological awareness. Relative cost estimates suggest that refractive screening programs can detect visual problems in infancy at lower overall cost than surveillance in primary care. Conclusions. Photo/videorefraction can successfully screen infants for refractive errors, with visual outcomes improved through early refractive correction. Infant hyperopia is associated with mild delays across many aspects of visuocognitive and visuomotor development. These studies raise the possibility that infant refractive screening can identify not only visual problems, but also potential developmental and learning difficulties.

Basal ganglia damage and impaired visual function in the newborn infant

AIM To examine the effects of early lesions in the visual pathway on visual function; and to identify early prognostic indicators of visual abnormalities. METHODS The visual function of 37 infants with perinatal brain lesions on magnetic resonance imaging was assessed using behavioural and electrophysiological variables. RESULTS Normal visual behaviour was observed in most infants with large bilateral occipital lesions, but all the infants with associated basal ganglia involvement had abnormal visual function. Visual abnormalities were also present in six infants with isolated basal ganglia lesions. CONCLUSIONS These observations suggest that basal ganglia may have an integral role in human visual development and that their presence on neonatal MRI could be an early marker of abnormal visual function. Key messages • In agreement with previous animal studies, our study has suggested that basal ganglia may play an important role in infant’s vision. • The involvement of basal ganglia on neonatal MRI, seems to be more often associated with impaired visual function than lesions involving the visual occipital cortex. • A wide battery of tests is necessary to evaluate various aspects of visual function.

Infant vision screening predicts failures on motor and cognitive tests up to school age

In a population-based infant vision screening programme, 5295 infants were screened and those with significant refractive errors were followed up. To assess the relationship between the development of vision and other domains, we report a longitudinal study comparing infants with significant hyperopia, identified at age 9 months (‘hyperopes’) with infants with normal refractions (‘controls’). Children are included who completed at each age a broad set of visual, cognitive, motor and language measures taken over a series of follow-up visits up to age 5.5 years. Hyperopes performed significantly worse than controls on the Atkinson Battery of Child Development for Examining Functional Vision at 14 months and 3.5 years and the Henderson Movement Assessment Battery for Children at 3.5 and 5.5 years. The Griffiths Child Development Scales, MacArthur Communicative Development Inventory and British Picture Vocabulary Scales showed no significant differences. Exclusion of those infants who became amblyopic and strabismic did not substantially alter these results, suggesting that the differences between groups were not a consequence of these disorders. These results indicate that early hyperopia is associated with a range of developmental deficits that persist at least to age 5.5 years. These effects are concentrated in visuocognitive and visuomotor domains rather than the linguistic domain.

Visual function in term infants with hypoxic-ischaemic insults: correlation with neurodevelopment at 2 years of age

AIMS To determine if there is any association between the findings of visual assessment performed at the age of 5 months and neurodevelopmental outcome at the age of 2 years in children who have sustained hypoxic-ischaemic insults. METHODS Twenty nine term infants with hypoxic–ischaemic encephalopathy and/or brain lesions on neonatal magnetic resonance imaging (MRI) were prospectively evaluated. At 5 months of age all the infants had their visual function assessed using the Atkinson Battery of Child Development for Examining Functional Vision, which includes the assessments of optokinetic nystagmus (OKN), acuity, visual fields, fixation shift and phase and orientation reversal visual evoked potentials. At 2 years of age the children had a structured neurological evaluation and a Griffiths developmental assessment. RESULTS There was good correlation between the extent of the early detected visual impairment and both neuromotor and global development. Children with more than three out of five abnormal visual tests at 5 months of age tended to have abnormal neurological examination results and abnormal developmental quotients. Children with three or fewer abnormalities tended to have developmental quotients in the normal range; the level of their performance, however, was still related to the number of visual tests passed. CONCLUSIONS Individual visual tests can provide important prognostic information. While abnormal OKN and acuity were always associated with abnormal outcome, normal results on visual evoked potentials and fixation shift tended to be associated with normal outcome.

Visual function and perinatal focal cerebral infarction.

AIMS: To evaluate the visual function of infants with perinatal cerebral infarction in whom the site and size of the lesion has been determined using magnetic resonance imaging (MRI). METHODS: Twelve infants with cerebral infarction on MRI were studied with a battery of tests specifically designed to evaluate visual function in infancy. This included tests: for visual attention (fixation shifts); of cerebral asymmetry (optokinetic nystagmus, visual fields); for assessment of acuity (forced choice preferential looking); and neurophysiological measures of vision (phase reversal and orientation reversal visual evoked potential). RESULTS: A considerable incidence of abnormalities on at least one of the tests for visual function used was observed. The presence or severity of visual abnormalities could not always be predicted by the site and extent of the lesion seen on imaging. CONCLUSIONS: Early focal lesions affecting the visual pathway can, to some extent, be compensated for by the immature developing brain. These data suggest that all the infants presenting with focal lesions need to be investigated with a detailed assessment of various aspects of vision.

Cortical vision, MRI and developmental outcome in preterm infants

Objectives: To test two measures of visual cortical function in the first year of life as early markers of functionally significant brain damage in infants born preterm: orientation-reversal visual event-related potentials (OR-VERP) and a behavioural test of cortically controlled visual attention-fixation shifts under competition (FS). Also to examine how these measures relate to (1) perinatal brain insults identified by MRI, and (2) later neurodevelopmental status. Patients and methods: After neonatal and term-age-equivalent MRI, 26 preterm infants (<32 weeks of gestational age, mean 28.1 weeks) were given the OR-VERP and FS tests before 12 months post-term age and a neurodevelopmental assessment (Griffiths Scales) at 2 years. MRI scans examined for parenchymal lesions, intraventricular haemorrhage, ventricular dilatation and diffuse excessive high signal intensity were classified into three categories of severity. Cortical visual test results were compared across these categories and examined as predictors of developmental status at 2 years. Results: 26 infants were studied. 13/25 infants showed significant OR-VERP responses. 12/26 showed normal FS performance. On both tests, the proportion of infants meeting these criteria decreased significantly with MRI severity. As predictors of Griffiths developmental quotient ⩽80, the FS test had a sensitivity of 100%, a specificity of 61%, and positive and negative predictive values of 50% and 100%, respectively; corresponding values for OR-VERP were 86%, 65%, 50% and 92% . Conclusions: Visual cortical tests can provide early indicators of the functional impact of perinatal brain damage in the preterm infant.

Neonatal cerebral infarction and visual function at school age

Objective: To assess various aspects of visual function at school age in children with neonatal cerebral infarction. Patients and methods: Sixteen children born at term, who had cerebral infarction of perinatal onset on neonatal magnetic resonance imaging (MRI) were assessed using a battery of visual tests. This included measures of crowding acuity (Cambridge Crowding Cards), stereopsis (TNO test), and visual fields. The results of the visual assessment were compared with the type and the extent of the lesion observed on neonatal MRI. Results: Only six of the 16 children (28%) had some abnormalities of visual function on these tests. Visual abnormalities were more common in children with more extensive lesions involving the main branch of the middle cerebral artery and were less often associated with lesions in the territory of one of the cortical branches of the middle cerebral artery. The presence of visual abnormalities was not always associated with the involvement of optic radiations or occipital primary visual cortex. Abnormal visual fields were only found in children who also developed hemiplegia. Conclusions: Abnormality of visual function is not common in children who had neonatal infarction and, when present, tends to be associated with hemiplegia and more extensive lesions.