Visual development

BACKGROUND: The Illinois College of Optometry's (ICO) Pediatric Outreach Program (POP) provides comprehensive vision care for high-risk children from birth to approximately 5 years of age in partnership with early intervention programs throughout the city of Chicago. Grant funds assisted in the ability to deliver vision services and spectacles to uninsured children. This report describes the structure and organization of the POP and presents the visual data. METHODS: Comprehensive eye examinations were performed on 4,298 children ages birth to approximately 5 years at 76 early intervention program sites. All of the children evaluated were enrolled from early intervention/Head Start programs. Visual acuity determination (by Lea method), assessment of binocular status, stereopsis evaluation, cycloplegic retinoscopy, and ocular health evaluations were performed. As necessary, eyeglasses were prescribed. Amblyogenic risk factors, strabismus, and ocular pathology were identified. RESULTS: Of the 4,298 children examined, 49% were boys and 51% were girls. Two percent were younger than 12 months old, 6% were 1.1 to 2 years old, 12% were 2.1 to 3 years, 30% were 3.1 to 4 years, 35% were 4.1 to 5 years, 14% were 5.1 to 6 years, and 1% were older than 6 years. Hyperopia and emmetropia were the most common refractive classifications among the children examined. Approximately 6.5% had risk factors for isometropic amblyopia, and 2.3% had risk factors for anisometropic amblyopia. Approximately 1% of the children had strabismus. Less than 1% of the children examined were identified with ocular pathology. Spectacles were dispensed to 16.6% of the children examined. CONCLUSIONS: The Pediatric Outreach Program provides early identification and treatment of abnormal visual conditions, ensuring that children have maximal visual acuity and visual function. The educational aspects of the program have also contributed to its successes. Education for parents and early intervention agency staff promote the importance of comprehensive vision examinations for children 5 years of age and younger.

The present paper evaluates the most recent randomized controlled trials assessing the efficacy of n-3 LCPUFA supplementation (with or without n-6 LCPUFA) during pregnancy, lactation, infancy and childhood on visual and cognitive development. Available evidence suggests a beneficial effect of maternal n-3 LCPUFA supplementation during pregnancy and lactation on cognitive development of infants and children, but not for visual development. Evidence for an effect of LCPUFA supplementation of preterm and term infants on cognitive development of infants remains inconclusive. However, supplementing term infants with daily doses of 100 mg docosahexaenoic acid plus 200 mg arachidonic acid improves visual development as measured by electrophysiological tests. Evidence for benefits of n-3 LCPUFA on cognitive development in healthy children older than 2 years of age is too limited to allow a clear conclusion. Taken together, the evidence for potential benefits of LCPUFA supplementation is promising but yet inconclusive.

Extreme natural ambient light reduction, in both energy and range of wavelength spectrum, occurs during the winter season at very high latitudes (above the Arctic Circle or 66°32 0 North) that in turn results in increased exposure to artificial lighting. In contrast, during the summer months, the sun remains above the horizon and there is no darkness or night. Little is known about these extreme changes in light exposure on human visual perception. Measuring color discriminations with the FM100 Test revealed that Norwegians born above the Arctic Circle were less sensitive to yellow-green, green, and green-blue spectrum differences whereas they were more sensitive to hue variations in the purple range than individuals born below the Arctic Circle. Additionally, it was found that the Norwegian individuals born above the Arctic Circle and during autumn showed an overall decrease in color sensitivity, whereas those born in the summer showed a relative increase. All participants were adults and their color vision was tested in the same location (i.e., in Tromsø at 69.7°N orth). These findings are consistent with the idea that there is a measurable impact on colour vision as adults of the photic environment that individuals born above the Arctic Circle and in the autumn experienced during infancy, namely a reduction in exposure to direct sunlight and an increase in exposure to twilight and artificial lighting.

To determine the prevalence, nature, and degree of accommodative dysfunction among children with different types and severities of cerebral palsy (CP) in Northern Ireland. METHODS. Ninety subjects with CP (aged 4 -15 years) were recruited through the Northern Ireland CP Register (NICPR). Modified Nott dynamic retinoscopy was used to measure lag and lead of accommodation at three test distances: 25 cm (4 D), 16.7 cm (6 D), and 10 cm (10 D) with the distance correction in place. Accommodative function was also assessed in an age-matched control group (n ϭ 125) for comparison. Each subject's neurologic status was derived from the NICPR. RESULTS. Children with CP demonstrate significantly reduced accommodative responses compared with their neurologically normal peers. Of the subjects with CP, 57.6% demonstrated an accommodative lag outside normal limits at one or more distances. Reduced accommodative responses were significantly associated with more severe motor and intellectual impairments (ANOVA P ϭ 0.001, P Ͻ 0.01, respectively). CONCLUSIONS. Brain injury such as that present in CP has a significant impact on accommodative function. These findings have implications for the optometric care of children with CP and inform our understanding of the impact of early brain injury on visual development. (Invest Ophthalmol Vis Sci.

Object perception and pattern vision depend fundamentally upon the extraction of contours from the visual environment. In adulthood, contour or edge-level processing is supported by the Gestalt heuristics of proximity, collinearity, and closure. Less is known, however, about the developmental trajectory of contour detection and contour integration. Within the physiology of the visual system, long-range horizontal connections in V1 and V2 are the likely candidates for implementing these heuristics. While post-mortem anatomical studies of human infants suggest that horizontal interconnections reach maturity by the second year of life, psychophysical research with infants and children suggests a considerably more protracted development. In the present review, data from infancy to adulthood will be discussed in order to track the development of contour detection and integration. The goal of this review is thus to integrate the development of contour detection and integration with research regarding the development of underlying neural circuitry. We conclude that the ontogeny of this system is best characterized as a developmentally extended period of associative acquisition whereby horizontal connectivity becomes functional over longer and longer distances, thus becoming able to effectively integrate over greater spans of visual space.

PURPOSE. Studies in nonhuman primates show that monocular visual deprivation starting at different ages has different effects on cells in the parvocellular and magnocellular laminae of the lateral geniculate nucleus. The present study used color and luminance contrast sensitivity (CS) measurements to look for differences in parvocellular-and magnocellular-related visual function in human subjects with strabismic amblyopia. METHODS. Fifteen subjects with early-and 14 with late-onset strabismic amblyopia and similar ranges of visual acuity were studied, together with 15 subjects with normal vision. Contrast sensitivities were measured to an equiluminant (L-M conemodulated) grating with slow onset and an achromatic (LϩM cone-modulated) 0.8-cpd grating with rapid onset using an adaptive method. RESULTS. Luminance and color CS were lower in the amblyopic eyes than in the fellow eyes of all amblyopes. For luminance CS, this was due both to an increase in sensitivity of the fellow eye and to a reduction in sensitivity in the amblyopic eye. Color CS was greatly reduced in the amblyopic and fellow eyes of subjects with strabismic amblyopia of early-and late onset compared with subjects with normal vision. The reduction in color CS compared with luminance CS was significantly greater in eyes with late-rather than early-onset amblyopia. CONCLUSIONS. Parvocellular and magnocellular function are differentially affected in the amblyopic and fellow eyes of subjects with strabismic amblyopia. The difference is more marked in late-onset amblyopia than in early-onset amblyopia. (Invest Ophthalmol Vis Sci. 2006;47:4836 -4841)

Transient flash VEPs allow objective assessment of visual function and are easily recorded in young infants. However, due to their high variability, they are an insensitive surrogate marker of visual development. The aim of our study was to investigate the early maturation of temporal characteristics of steady-state flicker VEPs. Data from 53 VEP sessions were analyzed in term-born infants between birth and 20 months of age. The stimulus was a square-wave modulated luminance flicker with 80% modulation depth at temporal frequencies of 4.7, 7.5, 12.5, and 19 Hz. A total of 18 healthy adults aged between 21 and 54 years served as controls. Contingent on the stimulus frequency, we found pronounced changes of the flicker VEP with age. Regression lines fit to the first harmonic VEP magnitude as a function of age between 3 and 88 weeks of age indicated increases at 7.5 (P = 0.004), 12.5 (P \ 0.001), and 19 Hz (P = 0.07) and a non-significant decrease at 4.7 Hz (P = 0.3). The magnitude of the second harmonic increased for all frequencies (4.7 (P = 0.05), 7.5 (P = 0.01), 12.5 (P = 0.13), and 19 Hz (P = 0.18)). Over the whole infant age range, the flicker VEP was dominated by the first harmonic, in contrast to adults, where the response was typically shifted to a higher harmonic at low stimulus frequencies. The optimal stimulus frequency, defined as the frequency eliciting the highest magnitude for F1, shifted to higher rates with age. Due to the difference from adult responses, further developmental changes of the temporal properties must be assumed to occur after the age of 20 months. Changes in temporal characteristics of the flicker VEP with age may be useful as an indicator of visual system maturation and a useful tool to detect visual delay.