Visual function in low birthweight children

Prevalence and causes of ocular disorders and visual impairment among preterm children in Ethiopia

OBJECTIVE

The aim of this study was to determine the prevalence, causes of ocular disorders and visual impairment among preterm children previously admitted to neonatal intensive care units in Addis Ababa, Ethiopia.

METHODS AND ANALYSIS

A prospective screening survey was conducted from February to June 2019 at the paediatric eye clinic of Menelik II Hospital. Children who were preterm at birth and who attended the eye clinic were included in the study. Data on demographic and neonatal characteristics, neonatal and maternal comorbidities and ocular disorders were collected. OR and univariate analysis were used to identify predictors of ocular diseases and visual impairment.

RESULTS

There were 222 children included in the study with a mean age at presentation of 2.62 years (range 2.08-6.38 years), mean gestational age 34.11 weeks (range 30-36) weeks and mean birth weight 1941.72 g (range 953-3500 g). Nearly two-thirds had ocular disorders with refractive error (51.8%), strabismus (11.3%) and a history of retinopathy of prematurity (ROP) (7.2%) being more common. One-fourth of the children had visual impairment, and the prevalence of amblyopia was 40.1%. Uncorrected refractive errors, strabismus and ROP were causes for visual impairment.

CONCLUSION

Visual impairment and amblyopia are common in Ethiopia. There is a need to develop a screening protocol for ocular disorders for preterm children to enhance early detection and prevention of childhood visual impairment.

Wide-field digital imaging system for assessing ocular anterior segment development in very preterm infants

Purpose

This study aims to longitudinally investigate developments of the anterior segment in very preterm infants who exhibit normal retinal development outcomes by utilizing a wide-field digital imaging system.

Methods

Between June 2021 and June 2022, neonates with a birth weight of <1500 g and/or a gestational age (GA) of less than 32 weeks were included in this study. The participants underwent regular ocular examinations, including sequential evaluations of the anterior segment and the retina, at intervals of 2-5 weeks, starting from birth and continuing until they reached a corrected GA of 48 weeks. Term neonates were selected as normal controls for the study. The study recorded the weight and GA of subjects at the time of examination, as well as indicators of abnormal development in the anterior segment.

Results

A total of 48 very preterm infants with normal retinal developmental outcomes were enrolled. The control group included 59 full-term infants. Common anterior segment eye abnormalities such as persistent hyperplasia of primary vitreous, persistent pupillary membranes, iris vessels, and anterior chamber angle vessels gradually subsided with the period in very preterm infants. The vascularity of the iris was substantially higher than in term controls (P < 0.05) at term gestation. The imaging of iris vessels and anterior chamber angle vessels in very preterm infants exhibited a decline at 46 and 47 weeks, respectively, which occurred slightly later compared to term infants.

Conclusion

In very preterm infant s with normal outcomes, although the developmental process is delayed, they may form a normal anterior segment structure similar to that of full-term infants in the late stages, which is followed up by the wide-field digital imaging system.

Visual acuity, amblyopia, and vision-related quality of life in preterm adults with and without ROP: results from the Gutenberg prematurity eye study

Objectives

This study investigated the effects of prematurity and ROP on visual acuity and VRQoL in adults (18–52 years).

Methods

The Gutenberg Prematurity Eye Study is a retrospective cohort study with a prospective ophthalmologic examination. Preterm and full-term participants at an age from 18 to 52 years were included. Distant corrected visual acuity (DCVA) and VRQoL were assessed in participants (892 eyes of 450 individuals aged 28.6 ± 8.6 years, 251 females) grouped into full-term controls (gestational age [GA] at birth ≥37 weeks), preterm participants without ROP and GA 33–36 weeks (group 2), GA 29–32 weeks (group 3), GA ≤ 28 weeks (group 4), non-treated ROP (group 5) and treated ROP (group 6). Main outcome measures were distant corrected visual acuity (DCVA), VRQoL and prevalence of amblyopia.

Results

The DCVA of the better eye correlated (p < 0.001) with GA, birth weight, ROP, ROP treatment, and perinatal adverse events and was poorer in both ROP groups. Visual acuity of <20/200 in the better eye was observed in two participants (4.2%) in the ROP group and one person (6.7%) in the treated ROP group. The prevalence of amblyopia increased in the ROP groups. Compared to full-term controls, visual functioning VRQoL scores were lower in preterm individuals independent of ROP while socioemotional VRQoL scores were only lower in the treated ROP group.

Conclusion

Participants with postnatal ROP and its treatment showed decreased visual acuity and VRQol in adulthood, with amblyopia occurring more frequently in more preterm participants with ROP.

Real-World Visual Outcomes of Laser and Anti-VEGF Treatments for Retinopathy of Prematurity

PURPOSE

To characterize visual outcomes in children screened for retinopathy of prematurity (ROP).

DESIGN

Retrospective, interventional case series.

METHODS

Patients who received ROP screening examinations at UCLA Medical Centers and were followed with outpatient eye examinations at Stein Eye Institute and/or Doheny Eye Institute (Los Angeles, California) were included. Data were collected on birth characteristics, worst type of ROP, and ROP treatment. Adverse visual outcomes included myopia, strabismus, amblyopia, macular dragging, and optic atrophy. Snellen visual acuity was reported for children 4 years and older.

RESULTS

A total of 175 infants (350 eyes) were included for analysis (mean gestational age = 28.2 weeks and birth weight = 1059 g) from a screening population of 539 infants (1078 eyes, 32.4% follow-up) over a 9-year period. Fifteen eyes received primary anti-vascular endothelial growth factor (anti-VEGF) therapy, whereas 59 eyes received primary laser therapy. Primary anti-VEGF therapy, as compared with primary laser treatment, was associated with a decreased incidence of amblyopia (adjusted odds ratio [aOR] = 0.6-0.86, P < .0001) after controlling for gestational age and birth weight. The rates of optic atrophy (P = .79), strabismus (P = .98), and myopia (P = .93) were not different between anti-VEGF and laser treatment groups. Infants receiving anti-VEGF therapy had more posterior disease than laser-treated infants (P = .041). Infants receiving laser therapy were more likely to have severe myopia (aOR = 1.02-1.3, P = .023), amblyopia (aOR = 1.12-1.61, P = .002), and optic atrophy (aOR = 1.01-1.32, P = .045) than infants not treated.

CONCLUSION

These findings add to the advantages of anti-VEGF treatment compared with primary laser treatment, particularly in posterior ROP.

Technical Innovation for Visual Assessment of Preterm Newborns in a Neonatal Intensive Care Unit: Exploratory Study

Objective

The present study is aimed at assessing heart rate variability (HRV) and its correlation with visual acuity (VA) assessment of preterm newborns (PTNB) in neonatal intensive care units.

Method

Cross-sectional study analyzing HRV during assessment of VA with the aid of a Polar RS800CX heart rate monitor (Polar Electro Oy, Finland). HRV was analyzed according to time and frequency domains and the chaos domain used the autocorrelation coefficient and entropy. The sample consisted of hospitalized PTNB, and static analysis included simple regression diagnosis.

Results

A total of 14 PTNB were included in the sample. VA varied between 0.23 and 1.60 cpd, and only five PTNB obtained below-expected values for age. Statistical analysis demonstrated a negative correlation between VA and time domain (SDDN and SD2) and a positive correlation between frequency domain (heart rate and hertz), but in simple linear regression analysis, these variables did not influence VA.

Conclusion

The results of the study demonstrate that visual acuity was inversely correlated with SDNN and SD2 and during stimulation, showing that the higher the visual performance, the lower the autonomic modulation response.

Thyroid Activating Enzyme, Deiodinase II Is Required for Photoreceptor Function in the Mouse Model of Retinopathy of Prematurity

Purpose

Retinopathy of prematurity (ROP) is a severe complication of premature infants, leading to vision loss when untreated. Presently, the molecular mechanisms underlying ROP are still far from being clearly understood. This study sought to investigate whether thyroid hormone (TH) signaling contributes to the neuropathology of ROP using the mouse model of ROP to evaluate longitudinal photoreceptor function.

Methods

Animals were exposed to hyperoxia from P7 to P12 to induce retinopathy, thereafter the animals were returned to room air (normoxia). The thyroid-activating enzyme type 2 deiodinases (Dio2) knockout (KO) mice and the littermate controls that were exposed to hyperoxia or maintained in room air and were then analyzed. The retinal function was evaluated using electroretinograms (ERGs) at three and seven weeks followed by histologic assessments with neuronal markers to detect cellular changes in the retina. Rhodopsin protein levels were measured to validate the results obtained from the immunofluorescence analyses.

Results

In the ROP group, the photoreceptor ERG responses are considerably lower both in the control and the Dio2 KO animals at P23 compared to the non-ROP group. In agreement with the ERG responses, loss of Dio2 results in mislocalized cone nuclei, and abnormal rod bipolar cell dendrites extending into the outer nuclear layer. The retinal function is compromised in the adult Dio2 KO animals, although the cellular changes are less severe. Despite the reduction in scotopic a-wave amplitudes, rhodopsin levels are similar in the adult mice, across all genotypes irrespective of exposure to hyperoxia.

Conclusions

Using the mouse model of ROP, we show that loss of Dio2 exacerbates the effects of hyperoxia-induced retinal deficits that persist in the adults. Our data suggest that aberrant Dio2/TH signaling is an important factor in the pathophysiology of the visual dysfunction observed in the oxygen-induced retinopathy model of ROP.

Early visual and neuro-development in preterm infants with and without retinopathy

BACKGROUND

Retinopathy of prematurity (ROP) is often associated with visual impairment and multiple developmental disabilities.

AIMS

As most of the previous studies include infants with brain lesions, that can determine visual impairment per se, a cohort of low neurological risk preterm infants without ROP and with various degree of severity of ROP was assessed in order to establish visual and neurodevelopmental outcome.

STUDY DESIGN

Preterm infants born at <31 weeks gestation, without major brain lesions, underwent visual function assessment at 1 year corrected age and neurodevelopmental assessment at 2 years corrected age.

SUBJECTS

One hundred and five infants were included in the study: 42 infants did not develop ROP, 7 reached stage 1 in zone 2 ROP, 37 reached prethreshold (untreated) type 2 ROP. The remaining 19 infants were classified as type 1 ROP.

OUTCOME MEASURES

Visual function (including fixing, tracking, visual acuity, visual field, attention at distance and nystagmus) were assessed at 12 months corrected age and Griffiths Scales at 2 years corrected age.

RESULTS

The severity of ROP was strongly correlated (p < 0.001) with both visual function at 1 year and neurodevelopment at 2 years. Similarly, the presence of nystagmus was also strongly correlated with visual and neurodevelopmental sequelae.

CONCLUSIONS

Infants with no or milder retinopathy showed normal visual function at 1 year and neurodevelopment at 2 years. Infants who underwent treatment more frequently showed abnormal results on several aspects of visual function. Presence of nystagmus appeared to increase the risk for abnormal visual function and neurodevelopmental outcome.

Decreasing intraocular pressure significantly improves retinal vessel density, cytoarchitecture and visual function in rodent oxygen induced retinopathy

We attempted to explore a noninvasive, easily applicable and economically affordable therapy for retinopathy of prematurity (ROP). Rat pups were raised in 80% oxygen from postnatal day 7 to P12, and returned to room air. Travoprost eye drops were administered twice a day for 7 days, to reduce intraocular pressure (IOP) by about 20%. Immunohistochemical staining was performed to visualize vessel endothelial cells, to analyze retinal neurons and cytoarchitecture. Behavioral experiments were carried out to test visual acuity and contrast sensitivity. At the end of the 7-day treatment, the number of vessels extending to the vitreous body was significantly reduced and retinal vessel density increased. This improvement was maintained to the end of the 12th week. In the central retina of the model group, the horizontal cells were completely wiped out, the outer plexiform layer was undetectable, and the rod bipolar cell dendrites sprouted into the outer nuclear layer. The treatment partially reverted these architectural changes. Most importantly, behavioral experiments revealed significantly improved visual acuity and contrast sensitivity in the treated group. Therefore, reducing IOP could potentially serve as a safe and economical measure to treat ROP.

Visual configural processing in adults born at extremely low birth weight

Being born at extremely low birth weight (ELBW; ≤1,000 g) is associated with enduring visual impairments. We tested for long-term, higher order visual processing problems in the oldest known prospectively followed cohort of ELBW survivors. Configural processing (spacing among features of an object) was examined in 62 adults born at ELBW (M_age  = 31.9 years) and 82 adults born at normal birth weight (NBW; ≥2,500 g: M_age  = 32.5 years). Pairs of human faces, monkey faces, or houses were presented in a delayed match-to-sample task, where non-matching stimuli differed only in the spacing of their features. Discrimination accuracy for each stimulus type was compared between birth weight groups, adjusting for neurosensory impairment, visual acuity, binocular fusion ability, IQ, and sex. Both groups were better able to discriminate human faces than monkey faces (p < .001). However, the ELBW group discriminated between human faces (p < .001), between monkey faces (p < .001), and to some degree, between houses (p < .06), more poorly than NBW control participants, suggesting a general deficit in perceptual processing. Human face discrimination was related to performance IQ (PIQ) across groups, but especially among ELBW survivors. Coding (a PIQ subtest) also predicted human face discrimination in ELBW survivors, consistent with previously reported links between visuo-perceptive difficulties and regional slowing of cortical activity in individuals born preterm. Correlations with Coding suggested ELBW survivors may have used a feature-matching approach to processing human faces. Future studies could examine brain-based anatomical and functional evidence for altered face processing, as well as the social and memory consequences of face-processing deficits in ELBW survivors.

Central Corneal Thickness and Its Association with Birth Parameters in Chinese Adolescents

Purpose: To examine the distribution and determinants of central corneal thickness (CCT) including birth weight and gestational age in a school-based samples of Grade 7 students in rural China. Methods: 2346 (93.5%) grade 7 students with a mean age of 13.8 years participated in the study. CCT was measured for both eyes using the LenStar LS900. Information regarding birth weight and gestational age was retrieved from the participants' delivery records. A linear regression model was established to examine the relationship of birth weight, gestational age and other factors with CCT. Results: The mean CCT in this population was 534.7 µm and boys had a greater CCT compared with girls (P = .06). CCT was positively related to axial length (r = 0.056) while negatively related to anterior chamber depth (r = -0.076) and corneal power (r = -0.105) . In multivariate analyses, the cornea was 19.35µm thinner in individuals with low birth weight compared with those with normal. In addition, the cornea was 25.25µm thinner in prematurely born adolescents compared with full-term ones. The combined effect of birth weight and gestational age on CCT was not statistically significant (P for interaction = 0.12) Conclusions: Low birth weight and small gestational age are associated with thinner corneas in adolescence. This disparity across groups with different levels of birth parameters should be taken into account by future studies investigating CCT as risk factors or diagnostic tests for glaucoma.

Amblyopia Risk Factors in Premature Children in the First 3 Years of Life

PURPOSE

To determine the incidence of amblyopia risk factors during the first 3 years of life in premature children.

METHODS

This prospective cohort included 145 premature children (gestational age of less than 37 weeks) who were evaluated for amblyopia risk factors every 6 months until age 3 years. The incidence rate, cumulative incidence, and prevalence of any amblyopia risk factor were assessed in retinopathy of prematurity (ROP) and non-ROP screened groups. Multivariate logistic regression was performed to evaluate variables associated with the development of an amblyopia risk factor.

RESULTS

The 3-year incidence rates of amblyopia risk factors were similar between the non-ROP and ROP screened groups (18 versus 19 cases per 1,000 person-years, respectively). The 3-year cumulative incidence was also similar: 32% (95% confidence interval [CI]: 18 to 47) in the non-ROP and 14% (95% CI: 5 to 28) in the ROP screened group (P > .05). In the ROP screened group, the prevalence rates were 20% or greater at most time points. In the non-ROP screened group, the prevalence rates were 11% to 14% during the first 18 months and increased to more than 20% at 24 months and thereafter. Astigmatism was the most prevalent amblyopia risk factor in both groups (7% to 18%).

CONCLUSIONS

The incidence of amblyopia risk factors was not significantly different between non-ROP and ROP screened children in our cohort. The prevalence of refractive errors among premature non-ROP screened children was higher than that reported in childhood in the literature. It may be appropriate to screen all children with a history of prematurity for refractive errors around 24 months of age. [J Pediatr Ophthalmol Strabismus. 2019;56(2):88-94.].

Ocular outcomes and comorbidities in preterm infants enrolled for retinopathy of prematurity screening: A cohort study from western India

BACKGROUND

Retinopathy of prematurity (ROP) is emerging as an important cause of childhood blindness in middle-income countries such as India. Although blindness can be prevented in most cases with timely screening and treatment, certain ocular comorbidities can lead to visual impairment. We evaluated and compared 1-year visual, refractive, and structural outcomes and comorbidities in three subsets of preterm infants enrolled for screening of ROP.

SUBJECTS AND METHODS

Preterm children enrolled in the hospital's ROP screening program and with diagnosis of no ROP, mild ROP, or severe ROP were followed at 1 year of age to evaluate and compare visual, refractive, and structural outcomes as well as the presence of ocular comorbidities. Risk of poor outcome was calculated in children with mild and severe ROP reference population being children without ROP.

RESULTS

Eyes with severe ROP were at highest risk of poor visual (risk ratio [RR]: 3.5, P < 0.001), refractive (RR: 45, P < 0.001), and structural (RR: 11, P = 0.006) outcome as well as ocular comorbidities (RR 11, P < 0.001). Eyes with mild ROP were at higher risk of myopia (RR: 11, P = 0.06) and ocular comorbidities (RR: 4, P = 0.04). Sixteen (16%) of the eyes without ROP developed poor visual outcome.

CONCLUSION

Eyes with severe ROP are at highest risk of poor ocular outcomes and comorbidities and need a long-term follow-up. Eyes which do not develop ROP can have poor visual outcome and need to be assessed within the 1^st year of life.

[Electrophysiological characteristics of the retina in children with cicatrical retinopathy of prematurity]

Visual impairment in children with regressive retinopathy of prematurity (ROP) are diverse and widespread.

PURPOSE

to describe the electrophysiological characteristics of the retina in children with I-V stages of regressive ROP.

MATERIAL AND METHODS

The study included children with stages I-V aged 5 to 17 (in the disease stages of IV and V - with reattachment of the retina after surgical treatment of its detachment). Patients with concomitant diseases of the eye were excluded from the study. The main group included 133 children (163 eyes) aged 5 to 17 (mean age 7.2±0.3). Gestation age was 30.0±0.2 weeks, birth weight - 1368.0±46.6g. The control group consisted of 55 age-matched children. Standard electroretinogram (ERG) was performed in all study subjects. The amplitude-time characteristics of maximum and photopic response a- and b-waves were evaluated, and the b/a-index was calculated.

RESULTS

Visual acuity of 0.6 or higher was observed in 18 eyes (54.5%) of children with stage I-II ROP and significantly less in the disease stages of III and IVa - 29.5% and 15.6% respectively (p<0.01: Φ=2,717-3,663). In patients with IVb-V stages in 94.1% of cases visual acuity was lower than 0.1. Anamnesis showed significant decrease in photopic ERG starting with active period of stage III ROP. The retinal function further progressively decreased with stages. b/a index of maximum ERG increased proportionally to the severity of ROP active period. Core b/a index was significantly reduced in all stages of ROP (p<0.05).

CONCLUSION

Even the early stages of ROP have consequences for the functional status of the retina in premature infants; it is accompanied by significant disturbance of its electrogenesis.

Association of low birth weight with myopic refractive error and lower visual acuity in adulthood: results from the population-based Gutenberg Health Study (GHS)

Purpose

Low birth weight (BW) is linked to impaired organ development in childhood, including altered ocular morphological and functional development. The aim of this study was to evaluate whether low BW has long-term effects on visual acuity and refraction in adulthood.

Methods

The Gutenberg Health Study is a population-based, observational cohort study in Germany, including 15 010 participants aged between 35 and 74 years. These participants were divided into three different BW groups (low: <2500 g; normal: between 2500 and 4000 g; and high: >4000 g). Best-corrected visual acuity and objective refraction were examined. We used multivariable linear regression models with adjustment for age, sex, socioeconomic status and self-reported glaucoma, age-related macular degeneration, corneal disease and cataract to assess associations between BW and the main outcome measures, best-corrected visual acuity, spherical equivalent and astigmatism.

Results

Overall, 8369 participants reported their BW. In a multivariable analysis, an association for low BW with spherical equivalent (B=−0.28 per dioptre, P=0.005) and best-corrected visual acuity (B=0.02 logarithm of the minimum angle of resolution, P=0.006) compared with normal BW was observed. For participants with high BW, an association was observed with spherical equivalent (B=0.29 per dioptre, P<0.001), while none with visual acuity.

Conclusions

Our data demonstrated that low BW is linked to visual acuity and refractive long-term outcomes long after childhood. Individuals with low BW are more likely to have lower visual acuity and a higher myopic refractive error in adulthood. Adults with high BW are more likely to have a more hyperopic refractive error.

Ocular Findings in Low Birthweight and Premature Babies in the First Year: Do We Need to Screen?

Purpose

There is no standardized approach for the ophthalmic care follow-up of children screened for retinopathy of prematurity (ROP). The authors report the ocular findings at 12 months in preterm and low birthweight babies screened for ROP over a 5-year period (1998–2003).

Methods

The case notes of 211 babies were retrospectively reviewed for birth details, maternal details, presence of ROP, and findings at follow-up screening which included visual acuity, refraction at 12 months, presence of squint, and any other ocular problems.

Results

At 1 year follow-up, 16.6% of ROP positive children failed a screening visit because of squint (6.66%), refractive error (6.66%), and optic nerve abnormalities (3.33%). At 1 year follow-up, 10% of ROP negative children had failed a screening visit because of squint (3.75 %), refractive error (3.75%), and other pathology (2.5%).

Conclusions

The authors recommend screening all babies with ROP at 12 months to identify amblyogenic factors such as squint and refractive error. Parents of infants who do not develop ROP should be advised of the increased risk of visual problems in their children and to have their child examined in the preschool period.

Balance in children born prematurely currently aged 6–7

Study aim: Premature birth is one of the major problems of obstetrics, leading to numerous complications that are associated with prematurity, for instance balance disorders. The aim of the study was to assess the impact of premature birth on the ability to maintain balance in children commencing their school education. Material and methods: The study included children aged 6-7 years. The study group consisted of 59 children (31 girls and 28 boys, mean age 6.38 ± SD 0.73) born prematurely between 24 and 35 weeks of gestation. The control group consisted of 61 children (28 girls and 33 boys, mean age 6.42 ± 0.58) born at term. The research utilized standardized test tools - one-leg open-eyed and closed-eyed standing test, one-leg jumping test - and an original questionnaire survey. Results: The children born at term achieved better results in the majority of tests. The comparison of girls and boys born pre­maturely and at term showed no statistically significant difference between them in terms of dynamic balance, static balance or total balance control. The comparison of the tests performed on the right and left lower limb in prematurely born children showed no statistically significant differences. Conclusion: Premature birth affects the ability to maintain body balance. The results of the study indicate the need to develop coordination skills that shape body balance in prematurely born children.

Association of birth weight with corneal power in early adolescence: Results from the National Health and Nutrition Examination Survey (NHANES) 1999-2008

Purpose

To analyze the effect of birth weight on ocular morphology, refraction and visual function in early adolescents aged 12–15 years.

Material and methods

We conducted a secondary data analysis using the public use files from the National Health and Nutrition Examination Survey of the period from 1999 to 2008. Study participants aged 12 to 15 years were included with data on birth weight and ophthalmic parameters including presenting distance visual acuity, objective refraction and keratometry. Visual acuity, sphere, astigmatism in power vectors J₀ and J₄₅, corneal power and corneal astigmatism were evaluated for an association with birth weight. Linear and logistic regression with adjustment for age, sex, ethnicity, survey cycle and birth weight as independent variable were calculated.

Results

Linear regression analysis revealed an association between corneal power and birth weight (per 100g: beta = -0.04, p<0.001) in the univariate analysis, and in the model adjusted for age, sex, ethnicity and NHANES survey cycle (per 100g: beta = -0.04, p<0.001). A lower birth weight was associated with higher corneal power. We found no evidence for an association of visual acuity, sphere, spherical equivalent, J₀-vector and J₄₅-vector of astigmatism, corneal J₀- or corneal J₄₅-vector with birth weight.

Conclusion

Our data demonstrate that low BW is linked to alterations in keratometric power even in early adolescents aged 12–15 years whereas visual acuity and refractive error showed no association.

Pre- and Postnatal Development of the Eye: A Species Comparison

In this review paper, literature data on pre- and postnatal eye development are compared between humans and nonclinical species that are commonly used for human safety assessment, namely, mouse, rat, rabbit, dog, minipig, and nonhuman primates. Some new data on rat and minipig ocular development are also included. This compiled information can be helpful for species selection in juvenile toxicity studies or assist in the interpretation of (non)clinical data during pediatric drug development. Despite some differences in developmental windows and anatomical peculiarities, such as the lack of a fovea centralis in nonprimate species or the presence of a nictitating membrane in some nonclinical species, the functioning and development of the eye is strikingly similar between humans and other mammals. As such, all commonly used nonclinical species appear to be relatively good models for human eye development, although some practical constraints such as size may be a limiting factor. Birth Defects Research 109:1540-1567, 2017. © 2017 Wiley Periodicals, Inc.

Extrafoveal Cone Packing in Eyes With a History of Retinopathy of Prematurity

Purpose

To study the density and packing geometry of the extrafoveal cone photoreceptors in eyes with a history of retinopathy of prematurity (ROP). We used a multimodal combination of adaptive optics (AO) scanning light ophthalmoscopy (SLO) and optical coherence tomography (OCT).

Methods

Cones were identified in subjects (aged 14–26 years) with a history of ROP that was either severe and treated by laser ablation of avascular peripheral retina (TROP; n = 5) or mild and spontaneously resolved, untreated (UROP; n = 5), and in term-born controls (CT; n = 8). The AO-SLO images were obtained at temporal eccentricities 4.5°, 9°, 13.5°, and 18° using both confocal and offset apertures with simultaneous, colocal OCT images. Effects of group, eccentricity, and aperture were evaluated and the modalities compared.

Results

In the SLO images, cone density was lower and the packing pattern less regular in TROP, relative to CT and UROP retinae. Although SLO image quality appeared lower in TROP, root mean square (RMS) wavefront error did not differ among the groups. In TROP eyes, cone discrimination was easier in offset aperture images. There was no evidence of cone loss in the TROP OCT images.

Conclusions

Low cone density in TROP confocal SLO images may have resulted from lower image quality. Since AO correction in these eyes was equivalent to that of the control group, and OCT imaging showed no significant cone loss, the optical properties of the inner retina or properties of the cones themselves are likely altered in a way that affects photoreceptor imaging.

Relationship between Stereoscopic Vision, Visual Perception, and Microstructure Changes of Corpus Callosum and Occipital White Matter in the 4-Year-Old Very Low Birth Weight Children

Aim. To assess the relationship between stereoscopic vision, visual perception, and microstructure of the corpus callosum (CC) and occipital white matter, 61 children born with a mean birth weight of 1024 g (SD 270 g) were subjected to detailed ophthalmologic evaluation, Developmental Test of Visual Perception (DTVP-3), and diffusion tensor imaging (DTI) at the age of 4. Results. Abnormal stereoscopic vision was detected in 16 children. Children with abnormal stereoscopic vision had smaller CC (CC length: 53 ± 6 mm versus 61 ± 4 mm; p < 0.01; estimated CC area: 314 ± 106 mm² versus 446 ± 79 mm²; p < 0.01) and lower fractional anisotropy (FA) values in CC (FA value of rostrum/genu: 0.7 ± 0.09 versus 0.79 ± 0.07; p < 0.01; FA value of CC body: 0.74 ± 0.13 versus 0.82 ± 0.09; p = 0.03). We found a significant correlation between DTVP-3 scores, CC size, and FA values in rostrum and body. This correlation was unrelated to retinopathy of prematurity. Conclusions. Visual perceptive dysfunction in ex-preterm children without major sequelae of prematurity depends on more subtle changes in the brain microstructure, including CC. Role of interhemispheric connections in visual perception might be more complex than previously anticipated.

A Developmental Switch for Hebbian Plasticity

Hebbian forms of synaptic plasticity are required for the orderly development of sensory circuits in the brain and are powerful modulators of learning and memory in adulthood. During development, emergence of Hebbian plasticity leads to formation of functional circuits. By modeling the dynamics of neurotransmitter release during early postnatal cortical development we show that a developmentally regulated switch in vesicle exocytosis mode triggers associative (i.e. Hebbian) plasticity. Early in development spontaneous vesicle exocytosis (SVE), often considered as 'synaptic noise', is important for homogenization of synaptic weights and maintenance of synaptic weights in the appropriate dynamic range. Our results demonstrate that SVE has a permissive, whereas subsequent evoked vesicle exocytosis (EVE) has an instructive role in the expression of Hebbian plasticity. A timed onset for Hebbian plasticity can be achieved by switching from SVE to EVE and the balance between SVE and EVE can control the effective rate of Hebbian plasticity. We further show that this developmental switch in neurotransmitter release mode enables maturation of spike-timing dependent plasticity. A mis-timed or inadequate SVE to EVE switch may lead to malformation of brain networks thereby contributing to the etiology of neurodevelopmental disorders.

Neurotransmitter release is the principal form of chemical communication in the brain. When an action potential reaches a synapse, calcium influx activates the machinery for neurotransmitter release. During early neuronal development this machinery matures such that neurotransmitter release becomes time-locked to action potentials. By modeling this change in neurotransmitter release, we mechanistically show that the maturation process can be solely responsible for switching on associative (i.e. Hebbian) plasticity in the brain. The relevant proteins of the release machinery can thereby regulate the rate at which neural circuits represent sensory input, providing a novel mechanism to control the learning rate and onset. Appropriately timing of the onset of Hebbian plasticity is important because during early development sensory experience fine-tunes, often irreversibly, the neural wiring in our brain.

Is preterm birth a human-specific syndrome?

Human preterm birth (PTB), a multifactorial syndrome affecting offspring born before 37 completed weeks of gestation, is the leading cause of newborn death worldwide. Remarkably, the degree to which early parturition contributes to mortality in other placental mammals remains unclear. To gain insights on whether PTB is a human-specific syndrome, we examined within- and between-species variation in gestation length across placental mammals and the impact of early parturition on offspring fitness. Within species, gestation length is normally distributed, and all species appear to occasionally give birth before the 'optimal' time. Furthermore, human gestation length, like that of many mammalian species, scales proportionally to body mass, suggesting that this trait, like many others, is constrained by body size. Premature humans suffer from numerous cognitive impairments, but little is known of cognitive impairments in other placental mammals. Human gestation differs in the timing of the 'brain growth spurt', where unlike many mammals, including closely related primates, the trajectory of human brain growth directly overlaps with the parturition time window. Thus, although all mammals experience early parturition, the fitness costs imposed by the cognitive impairments may be unique to our species. Describing PTB broadly in mammals opens avenues for comparative studies on the physiological and genetic regulators of birth timing as well as the development of new mammalian models of the disease.

Refraction and visual acuity in a national Danish cohort of 4-year-old children of extremely preterm delivery

PURPOSE

A recent threefold increase in laser treatment for advanced retinopathy of prematurity (ROP) triggered a nationwide preschool ophthalmic and developmental status among extremely preterm survivors. Here, we discuss refraction and visual acuity.

METHODS

Survivors (n = 178) from a national birth cohort (February 2004 to March 2006) of gestational age <28 weeks (PT) and 56 full-term (FT) controls attended for evaluation at age 4 years. Cycloplegic refraction and keratometry were achieved by Retinomax autokeratorefractor and visual acuities by symbol recognition (HOTV, logMAR).

RESULTS

The refractive distribution presented a myopic tail (4.5%) and a hyperopic tail (11.9% ≥+2.5 D) as special preterm features, and corneas were more curved. Astigmatism and anisometropia were only marginally increased, and visual acuities were generally good. Best-corrected binocular median logMAR visual acuity was 0.1 in FT and 0.2 in PT, in Snellen equivalents 0.8 and 0.63. Snellen acuity ≤0.5 occurred across the ROP subgroups, but mainly in those with at least ROP stage 3. Two children had low vision.

CONCLUSIONS

The overall fair outcome for refraction and function is in accordance with other recent northern Europe experience. The results differ in particular from the poorer ophthalmic outcomes reported in the pioneer US treatment studies (cryotherapy for ROP and ETROP). The diode laser ablations (n = 32) appeared effective in our series; except one child, all treated subjects had good or fair social vision at the age of 4 years.

Impact of retinopathy of prematurity on ocular structures and visual functions

The preterm baby may develop ophthalmic sequelae which can be due to prematurity per se, due to retinopathy of prematurity (ROP) or due to neurological damage. Focusing on the former two, we discuss how in high-income countries the risk of sight-threatening ROP is largely confined to babies <1000 g birth weight (BW), whereas in low-income or middle-income countries babies exceeding 2500 g BW can be blinded. The effects of prematurity and ROP are presented as regional and global estimates of acute-phase ROP and the consequent mild/moderate and severe visual impairment. We discuss sequelae and how they affect the eye and its shape, strabismus and finally consider their impact on visual functions, including visual acuity, the visual field, colour vision and contrast sensitivity.

Delay in retinal photoreceptor development in very preterm compared to term infants

PURPOSE

We compared photoreceptor development from spectral domain optical coherence tomography (SD-OCT) imaging in very preterm infants (VPT, <32 weeks gestational age) with those of term infants.

METHODS

The microanatomy of foveal SD-OCT images obtained at the bedside at 37 to 42 weeks term equivalent postmenstrual age (TEA) was reviewed with qualitative and quantitative analysis of retinal and especially photoreceptor layers in the macula. Measures of maturity included presence of the cone outer segment tips (COST) or the ellipsoid zone (EZ) at foveal center, distance from Bruch's membrane (BM) to the EZ at the foveal center, and radial distance from foveal center to first appearance of the EZ.

RESULTS

The incidence of the EZ developed at the foveal center was lower in VPT infants (9/64, 14%) versus term infants (22/47, 47%, P < 0.001) and lower in VPT infants with macular edema (3/46) versus VPT without edema (6/18, P = 0.01). Mean ± SD distance from the foveal center to the visible EZ was 783 ± 440 μm in VPT, and 492 ± 501 μm in term infants, P = 0.002. The height of the BM-to-EZ at the foveal center did not differ in VPT versus term infants. The COST band was not visible in any infant.

CONCLUSIONS

Photoreceptor inner and outer segment development in VPT infants appears delayed when compared to term infants, and the photoreceptor RPE junction remains immature in all infants at TEA. Delayed maturation of photoreceptors could contribute to differences in visual function in some VPT infants.

Common visual problems in children with disability

Children with disability are at a substantially higher risk of visual impairment (VI) (10.5% compared with 0.16%) but also of ocular disorders of all types, including refractive errors and strabismus. The aetiology of VI in children with disability reflects that of the general population and includes cerebral VI, optic atrophy, as well as primary visual disorders such as retinal dystrophies and structural eye anomalies. VI and other potentially correctable ocular disorders may not be recognised without careful assessment and are frequently unidentified in children with complex needs. Although assessment may be more challenging than in other children, identifying these potential additional barriers to learning and development may be critical. There is a need to develop clearer guidelines, referral pathways and closer working between all professionals involved in the care of children with disability and visual disorders to improve our focus on the assessment of vision and outcomes for children with disability.

Choroidal thickness in regressed retinopathy of prematurity

PURPOSE

To compare choroidal thickness in patients with regressed retinopathy of prematurity (ROP) with healthy controls using enhanced depth imaging optical coherence tomography (EDI OCT) METHODS: Twenty-four children and young adults (41 eyes) with regressed ROP≥stage 3 had undergone EDI OCT with Spectralis FD-OCT as part of their clinical record. Their refraction, best-corrected visual acuity, and ophthalmoscopic findings were recorded. Corresponding data was collected prospectively from 33 healthy controls (58 eyes) who had been born at term. Choroidal thickness was measured independently by two observers subfoveally and at 1500 μm nasal and temporal to the fovea using EDI OCT.

RESULTS

Mean subfoveal choroidal thickness, adjusted for refraction, was 271.1 μm (95% CI, 247.8-294.5) in the ex-ROP group, which was significantly thinner than 327.4 μm (95% CI, 293.8-360.9) in controls (P=0.008). Similarly, mean adjusted temporal choroidal thickness was 257.2 μm (95% CI, 240.2-274.2) in ex-ROP's vs 320.5 μm (95% CI, 288.6-352.3) in controls (P=0.001). There was no statistically significant difference in the nasal measurement. In the ex-ROP group, there was no significant correlation between subfoveal choroidal thickness and gestational age (r(s)=0.16, P=0.46) or birthweight (r(s)=0.03, P=0.90). In eyes without copathology in addition to regressed ROP (29 eyes, 19 patients), there was no significant correlation between subfoveal choroidal thickness and visual acuity.

CONCLUSIONS

Our findings of thinner subfoveal and temporal macular choroidal thickness in regressed ROP support the case for choroidal involvement in the pathogenesis of this condition.

Visual sensory and perceptive functioning in 5-year-old very preterm/very-low-birthweight children

AIM

To examine visual sensory and perceptive functions, study their interrelations, and explore associations between visual dysfunctions and intelligence in very preterm/very-low-birthweight (VP/VLBW) children.

METHOD

One-hundred and sixteen VP/VLBW children (57 males, 59 females; mean gestational age 30.1 wks, SD 2.3; mean corrected age 5 y 6 mo, SD 1 mo) and 73 term-born children (40 males, 33 females; mean gestational age 39.9 wks, SD 1.3; mean age 5 y 6 mo, SD 3 mo) completed visual sensory (acuity, visual field, contrast-, color-, and stereovision), perceptive (visual coherence, and Developmental Test of Visual Perception non-motor scale), and intelligence assessments.

RESULTS

Compared with term-born children, VP/VLBW children had reduced acuity (d=0.70, p<0.001), inferior visual field (d=0.67, p<0.001), and stereovision (v=0.19, p=0.008). VP/VBLW children showed weaker static coherence (d=0.49, p=0.001) and Position in Space (d=0.41, p=0.006) performance, independent of visual sensory deficits, and showed lower Verbal IQ (VIQ) and Performance IQ (PIQ; p<0.001). Visual perceptive functioning accounted for 13% of variance in VIQ, and for 35% of variance in PIQ.

INTERPRETATION

Visual sensory and perceptive dysfunctions are present in VP/VLBW children and occur largely independently of each other. Visual perceptive dysfunctions are moderately associated with PIQ, and weakly with VIQ.

Fish-oil fat emulsion supplementation reduces the risk of retinopathy in very low birth weight infants: a prospective, randomized study

BACKGROUND

Preliminary studies suggest that fish-oil lipid emulsion given parenterally to very preterm infants reduces the severity of retinopathy (ROP) and cholestasis.

METHODS

Infants weighing <1250 g at birth were randomly allocated to 2 groups: an experimental group of 60 infants that received an intravenous (IV) soybean, olive oil, and fish oil emulsion, and a control group of 70 infants that was given a parenteral soybean and olive oil emulsion. Plasma and erythrocyte concentrations of docosahexaenoic acid (DHA) were determined using a high-performance liquid chromatography-mass spectrometry analysis.

RESULTS

Nine infants in the fish oil group required laser therapy for ROP compared with 22 infants in the standard intralipid group (risk ratio [RR], 0.48; 95% confidence interval [CI], 0.24-0.96). Three infants in the fish oil group developed cholestasis compared with 20 infants in the standard intralipid group (RR, 0.18; 95% CI, 0.055-0.56). The mean plasma DHA concentrations in treated infants were 2.9-fold higher in the fish oil group than in control infants on the 7th and 14th days of life. The mean DHA content in erythrocytes of treated infants was 4.5-fold and 2.7-fold higher compared with controls at 7 and 14 days of age.

CONCLUSIONS

Premature infants receiving an IV fat emulsion containing fish oil had less ROP requiring laser treatment and less cholestasis than those receiving a standard lipid emulsion. These infants also had higher plasma and erythrocyte DHA levels at 7 and 14 days, suggesting potential long-term neurodevelopmental benefits.

Alterations of the tunica vasculosa lentis in the rat model of retinopathy of prematurity

PURPOSE

To study the relationship between retinal and tunica vasculosa lentis (TVL) disease in retinopathy of prematurity (ROP). Although the clinical hallmark of ROP is abnormal retinal blood vessels, the vessels of the anterior segment, including the TVL, are also altered.

METHODS

ROP was induced in Long-Evans pigmented and Sprague Dawley albino rats; room-air-reared (RAR) rats served as controls. Then, fluorescein angiographic images of the TVL and retinal vessels were serially obtained with a scanning laser ophthalmoscope near the height of retinal vascular disease, ~20 days of age, and again at 30 and 64 days of age. Additionally, electroretinograms (ERGs) were obtained prior to the first imaging session. The TVL images were analyzed for percent coverage of the posterior lens. The tortuosity of the retinal arterioles was determined using Retinal Image multiScale Analysis (Gelman et al. in Invest Ophthalmol Vis Sci 46:4734-4738, 2005).

RESULTS

In the youngest ROP rats, the TVL was dense, while in RAR rats, it was relatively sparse. By 30 days, the TVL in RAR rats had almost fully regressed, while in ROP rats, it was still pronounced. By the final test age, the TVL had completely regressed in both ROP and RAR rats. In parallel, the tortuous retinal arterioles in ROP rats resolved with increasing age. ERG components indicating postreceptoral dysfunction, the b-wave, and oscillatory potentials were attenuated in ROP rats.

CONCLUSIONS

These findings underscore the retinal vascular abnormalities and, for the first time, show abnormal anterior segment vasculature in the rat model of ROP. There is delayed regression of the TVL in the rat model of ROP. This demonstrates that ROP is a disease of the whole eye.

Delayed luminance and chromatic contrast sensitivity in infants with spontaneously regressed retinopathy of prematurity

BACKGROUND

The current study assessed whether contrast sensitivity is affected in preterm infants with a history of spontaneously regressed retinopathy of prematurity (ROP, Stages 1-3). Specifically, we employed luminance (light/dark) and chromatic (red/green) stimuli, which are mediated by the magnocellular (M) and parvocellular (P) subcortical pathways, respectively.

METHODS

Contrast sensitivity (CS) was measured using forced-choice preferential looking testing in 21 infants with a history of ROP and 41 control preterm infants who were born prematurely but did not develop ROP, tested between 8 and 47 weeks (2-11 months) postterm age. Infants were presented with chromatic and luminance drifting sinusoidal gratings, which appeared randomly on the left or right side of the monitor in each trial. The contrast of the stimuli varied across trials and was defined in terms of root mean squared cone contrast for long- and medium-wavelength cones.

RESULTS

Between 8 and 25 weeks postterm, ROP infants had significantly worse CS, and there was a trend for greater impairment for luminance than chromatic CS. This delay was not seen at older ages between 26 and 47 weeks postterm.

CONCLUSIONS

These findings are consistent with the concept that early maturation of the M pathway is vulnerable to biological insult, as in the case of ROP, to a greater extent than in the P pathway.

Effects of prematurity on the development of contrast sensitivity: testing the visual experience hypothesis

In order to investigate the effects of visual experience on early visual development, the current study compared contrast sensitivity across infants born with different degrees of moderate-to-late prematurity. Here the logic is that at any given postterm age, the most premature infants will have the oldest postnatal age. Given that postnatal age is a proxy for visual experience, the visual experience hypothesis predicts that infants who are more premature, yet healthy, should have higher sensitivity. Luminance (light/dark) and chromatic (red/green) contrast sensitivities (CS) were measured in 236 healthy infants (born -10 to +2 weeks relative to due date) between 5 and 32 weeks postterm age from due date and 8-38 weeks postnatal from birth date. For chromatic CS, we found clear evidence that infants who were most premature within our sample had the highest sensitivity. Specifically, 4-10 additional weeks of visual experience, by virtue of being born early, enhanced chromatic CS. For luminance CS, similar but weaker results were seen. Here, only infants with an additional 6-10 weeks of visual experience, and only at later age points in development, showed enhanced sensitivity. However, CS in preterm infants was still below that of fullterm infants with equivalent postnatal age. In sum, these results suggest that chromatic CS is influenced more by prematurity (and possibly visual experience) than luminance CS, which has implications for differential development of parvocellular and magnocellular pathways.

Critical period for foveal fine structure in children with regressed retinopathy of prematurity

PURPOSE

Midgestation is a critical period in the formation of the foveal avascular zone. The authors evaluated the effects of preterm birth on foveal structure in children with regressed retinopathy of prematurity.

METHODS

Children with regressed retinopathy of prematurity with normal-appearing posterior poles (n = 26) and full-term control children (n = 56) were investigated. Frequency-domain optical coherence tomography 9-mm line scans across the fovea were obtained from right eyes. Using a customized segmentation program in MATLAB, total retinal thickness and the thickness of individual retinal layer regions were measured at the fovea (0°) and throughout ± 8°.

RESULTS

Total thickness of the fovea in the retinopathy of prematurity group (287.7 ± 47.6 μm) was greater than that in the control group (230.1 ± 18.2 μm). Bilinear fitting was performed to examine the relationship between total thickness and gestational age. Before 28 weeks, foveal thickness decreased with gestational age (14.3 μm/week); after 28 weeks, foveal thickness decreased only slightly (2.73 μm/week). Inner retinal layers contributed to the difference in thickness between groups more than outer layers. Foveal thickness was correlated with gestational age at birth but not with visual acuity or refractive error.

CONCLUSION

Preterm birth before 28 weeks of gestational age was associated with a failure of the inner retinal layers to migrate away from the fovea, resulting in increased foveal thickness.

My Voice Heard: The Journey of a Young Man with a Cerebral Visual Impairment

This longitudinal case study presents John's journey through childhood and adolescence, living with visual difficulties associated with a cerebral visual impairment. It highlights the day-to-day problems that John encountered, giving practical solutions and strategies that have enabled his dream of going to a university to be realized. John and his family are an inspiration.

Refractive Development in the "ROP Rat"

Although retinopathy of prematurity (ROP) is clinically characterized by abnormal retinal vessels at the posterior pole of the eye, it is also commonly characterized by vascular abnormalities in the anterior segment, visual dysfunction which is based in retinal dysfunction, and, most commonly of all, arrested eye growth and high refractive error, particularly (and paradoxically) myopia. The oxygen-induced retinopathy rat model of ROP presents neurovascular outcomes similar to the human disease, although it is not yet known if the "ROP rat" also models the small-eyed myopia characteristic of ROP. In this study, magnetic resonance images (MRIs) of albino (Sprague-Dawley) and pigmented (Long-Evans) ROP rat eyes, and age- and strain-matched room-air-reared (RAR) controls, were examined. The positions and curvatures of the various optical media were measured and the refractive state (℞) of each eye estimated based on a previously published model. Even in adulthood (postnatal day 50), Sprague-Dawley and Long-Evans ROP rats were significantly myopic compared to strain-matched controls. The myopia in the Long-Evans ROP rats was more severe than in the Sprague-Dawley ROP rats, which also had significantly shorter axial lengths. These data reveal the ROP rat to be a novel and potentially informative approach to investigating physiological mechanisms in myopia in general and the myopia peculiar to ROP in particular.

Cone function in children with a history of preterm birth

Color vision was examined by psychophysical tests and photopic color full-field electroretinography (ERG) in formerly preterm children, and compared with those of full-term children. In a prospective case-control study, 25 patients with a history of preterm birth 7-14 years of age were divided into three groups: group I, laser-treated retinopathy of prematurity [ROP] (n = 7); group II, spontaneously regressed ROP (n = 8); group III, no ROP (n = 10). Age-matched full-term born children comprised the control group (n = 8). Color vision was assessed by Fansworth D15 and Lanthony desaturated D15 tests. The cone function was tested using photopic full-field ERG. Besides the ISCEV standard stimuli, blue light on amber background was also used (S-cone ERG). The correlation between ERG parameters and prematurity or ROP was determined. We found no significant differences between any patient group and the control group in the results of the psychophysical tests, and implicit times of the ERG responses. The ERG b-wave amplitudes were significantly lower in group I (laser-treated ROP) compared to controls, for 2 of 4 stimulus conditions i.e. the standard (P = 0.028) and S-cone (P = 0.017) single flash ERGs. The general estimating equation model statistics found a significant effect of prematurity on the b-wave amplitudes (P = 0.025, standard, P = 0.014, S-cone ERG). A slightly reduced photopic ERG b-wave amplitude may be associated with prematurity.

Prediction of neurodevelopmental and sensory outcome at 5 years in Norwegian children born extremely preterm

OBJECTIVE

To examine the prevalence of neurodevelopmental disability and the predictive value of pre-, peri-, and postnatal data on neurologic, sensory, cognitive, and motor function in children born extremely preterm.

METHODS

This was a prospective observational study of all infants born in Norway between 1999 and 2000 with gestational ages between 22 and 27 weeks or birth weights between 500 and 999 g. Cognitive function was assessed with the Wechsler Preschool and Primary Scale of Intelligence-Revised, motor function with the Movement Assessment Battery for Children, and severity of cerebral palsy with the Gross Motor Function Classification for Cerebral Palsy. Disabilities were described as mild, moderate, or severe.

RESULTS

Of 371 eligible children, 306 (82%) were examined at a mean (SD) age of 5 years and 10 (4) months. For gestational age less than 28 weeks (n = 239), 26 (11%) children had cerebral palsy alone (n = 21) or in combination with blindness (n = 3) or deafness (n = 2); 1 was blind and 1 was deaf. Of the remaining children, the mean full-scale IQ was 94 ± 15, and significant predictors were (values given as the difference in IQ points [95% confidence intervals]) high maternal education (9.6 [5.7-13.4]), preeclampsia (-7.7 [-12.7 to -2.7]), and retinopathy of prematurity higher than grade 2 (-17.5 [-27.1 to -8.0]). Movement Assessment Battery for Children scores were positively associated with gestational age and prenatal steroids and negatively associated with being small for gestational age, male gender, and having retinopathy of prematurity. Moderate to severe neurodevelopmental disability was more common for gestational ages 25 weeks or less (28 of 87 children) than for 26 to 27 weeks (12 of 152 children; P < .001) and 28 weeks or more (7 of 67 children; P = .001).

CONCLUSIONS

The outcome was poorer for children with gestational ages of 25 weeks or less compared with those with gestational ages between 26 and 27 weeks. For those without cerebral palsy, blindness, or deafness, however, gestational age had a limited association with cognitive and motor function.

A conserved switch in sensory processing prepares developing neocortex for vision

Developing cortex generates endogenous activity that modulates the formation of functional units, but how this activity is altered to support mature function is poorly understood. Using recordings from the visual cortex of preterm human infants and neonatal rats, we report a "bursting" period of visual responsiveness during which the weak retinal output is amplified by endogenous network oscillations, enabling a primitive form of vision. This period ends shortly before delivery in humans and eye opening in rodents with an abrupt switch to the mature visual response. The switch is causally linked to the emergence of an activated state of continuous cortical activity dependent on the ascending neuromodulatory systems involved in arousal. This switch is sensory system specific but experience independent and also involves maturation of retinal processing. Thus, the early development of visual processing is governed by a conserved, intrinsic program that switches thalamocortical response properties in anticipation of patterned vision.

Flash visual evoked potentials at 2-year-old infants with different birth weights

BACKGROUND

Increased prevalence of visual impairments has been reported in preterm populations. However, it remains unclear about the long-term visual electrophysiological outcomes and their association with visual cognitive functions in premature infants. We investigated visual electrophysiological outcome of 2-year-old infants of different birth weights by flash visual evoked potentials (FVEPs) in order to explore the correlation between visual cognitive functions and FVEPs and to assess the application of FVEPs in evaluating the visual capability of an infant.

METHODS

The FVEPs of 77 infants, including 25 very low birth weight (VLBW) premature infants, 16 low birth weight (LBW) premature infants and 36 full-term infants, were tested with a visual electrophysiological testing device. Neuromotor development was assessed with the Bayley Scales of Infant Development, Second Edition (BSID-II). The visual cognitive functions were evaluated by scoring the proportion passed of 12 items chosen from the BSID-II for infants at 23 to 25 months of age.

RESULTS

The second prominent positive wave (P2) was the major component presented in all three groups. The mean latency of P2 in the VLBW, LBW and full-term groups was 149.65+/-23.79 ms, 129.39+/-8.70 ms, and 126.14+/-7.73 ms respectively. There was no significant difference in mean latency of P2 wave between the LBW and full-term groups; the mean latency of the P2 wave in the VLBW group was delayed more significantly than those of the other two groups. The difference in amplitude of the P2 peak to the preceding N2 peak (N2P2) between the three groups was not statistically significant. The latency of the P2 main wave was negatively correlated with mental developmental index (MDI) (r'(MDI) = -0.35) and visual cognitive capability (r'(visual capability) = -0.21).

CONCLUSIONS

The latency of the P2 main wave on FVEPs was delayed more significantly in premature infants than in full-term infants at 2 years of corrected age. The visual functional development was delayed in premature infants, especially in VLBW infants (gestational age <32 weeks). The FVEPs were reported low but there were statistically significant correlations between measures of visual cognition and P2 peak latency. As a noninvasive and convenient method, FVEPs are useful in assessing certain aspects of an infant's visual development and visual function.

Chromatic and luminance contrast sensitivity in fullterm and preterm infants

In order to investigate the contributions of visual experience vs. preprogrammed mechanisms on visual development, the current study compared contrast sensitivity in preterm vs. fullterm infants. If development is tied to time since conception, preterm infants should match the developmental trajectories of fullterm infants when plotted in postterm age. By contrast, if development is influenced by visual experience, preterm and fullterm infants should match when plotted in postnatal age. Luminance (light/dark) and chromatic (red/green) contrast sensitivities (CS) were measured in 25 preterm (born, on average, 6.6 weeks early) and 77 fullterm infants, between 1 and 6 months postterm. In the first few months, luminance CS was found to be predicted by postterm age, suggesting that preprogrammed development is sufficient to account for luminance CS. By contrast, chromatic CS exceeded that predicted by postterm age, which suggests that time since birth confers a benefit on chromatic CS. The preterms' 6.6 weeks of additional time since birth is roughly equivalent to 3.7 weeks of development in chromatic CS. In sum, these results suggest that chromatic CS is more influenced by early postnatal visual experience than luminance CS, which may have implications for development of parvocellular and magnocellular pathways.

The neurovascular retina in retinopathy of prematurity

The continuing worldwide epidemic of retinopathy of prematurity (ROP), a leading cause of childhood visual impairment, strongly motivates further research into mechanisms of the disease. Although the hallmark of ROP is abnormal retinal vasculature, a growing body of evidence supports a critical role for the neural retina in the ROP disease process. The age of onset of ROP coincides with the rapid developmental increase in rod photoreceptor outer segment length and rhodopsin content of the retina with escalation of energy demands. Using a combination of non-invasive electroretinographic (ERG), psychophysical, and image analysis procedures, the neural retina and its vasculature have been studied in prematurely born human subjects, both with and without ROP, and in rats that model the key vascular and neural parameters found in human ROP subjects. These data are compared to comprehensive numeric summaries of the neural and vascular features in normally developing human and rat retina. In rats, biochemical, anatomical, and molecular biological investigations are paired with the non-invasive assessments. ROP, even if mild, primarily and persistently alters the structure and function of photoreceptors. Post-receptor neurons and retinal vasculature, which are intimately related, are also affected by ROP; conspicuous neurovascular abnormalities disappear, but subtle structural anomalies and functional deficits may persist years after clinical ROP resolves. The data from human subjects and rat models identify photoreceptor and post-receptor targets for interventions that promise improved outcomes for children at risk for ROP.

Visual fields and optic disc morphology in very low birthweight adolescents examined with magnetic resonance imaging of the brain

PURPOSE

We aimed to evaluate visual fields (VFs) and optic disc morphology in very low birthweight (VLBW) adolescents compared with age- and gender-matched controls, and to relate the findings to magnetic resonance imaging (MRI) results.

METHODS

Fifty-nine VLBW adolescents and 55 age- and gender-matched controls with normal birthweight were examined. Visual fields were tested using computerized rarebit perimetry (RB). Optic nerve and retinal vessel morphology were evaluated by digital image analysis of fundus photographs. Brain MRI was conducted in the VLBW subjects.

RESULTS

Ten of the 57 VLBW subjects (p = 0.022) had subnormal VF results defined as a mean hit rate below the fifth percentile of the controls (i.e. < 89%). All of these also had significantly lower mean hit rates (p = 0.039) in the inferior hemifield. Sixteen of 57 (28%) VLBW subjects had white matter damage of immaturity (WMDI) on MRI. Six of 15 subjects with WMDI (who underwent VF testing) also had subnormal RB results, compared with four of 39 with normal MRI findings (p = 0.02). The mean neural retinal rim area was 9% smaller (p = 0.018) in the VLBW group than in the control group. The VLBW adolescents had a significantly higher index for tortuosity of arterioles than the controls (p < 0.001).

CONCLUSIONS

In the present study, 18% of all VLBW adolescents and 40% of those with WMDI had subnormal RB VF findings. The VLBW group had increased arterial tortuosity and a somewhat smaller (9%) mean neural retinal rim area than the control group. Thus sequels to VLBW appear to persist in adolescence.

Optic disc area and retinal area in amblyopia

PURPOSE

To compare retinal area to optic disc rim area ratios of hyperopic normal, strabismic eyes with equal acuity, amblyopic, and fellow eyes.

METHODS

Neuroretinal rim areas of 293 amblyopic and fellow eyes, and 77 non-amblyopic hyperopic right eyes, and 84 non-amblyopic strabismic right eyes were measured by magnification corrected retinal photography and planimetry. Retinal area estimates were based on axial lengths.

INCLUSION CRITERIA

All subjects had bilateral hyperopia. Patients with glaucoma or known optic nerve atrophy were excluded. The normal and strabismic groups had equal visual acuity in each eye better than 20/40. The amblyopic group had acuity worse than 20/40 in one eye uncorrectable with lenses and without gross anatomic defects.

RESULTS

The amblyopic group included 137 with strabismus and 89 with anisometropia exceeding 1.5 diopters. There were highly significant differences between the ratio of retinal area to optic disc rim area of the amblyopic and of normal eyes (unpaired t-test, p = 8.6 x 10(-6)), the amblyopic and strabismic right eyes (unpaired t-test, p = 4.22 x 10(-8)) as well between the fellow and amblyopic eyes (paired t-test, p = 2.13 x 10(-5)). The difference between the normal and strabismic eyes without amblyopia was not significant (p = 0.82). There was a 20 percent increase in the retinal receptor areas of hyperopic amblyopic eyes as compared to hyperopic eyes without amblyopia despite reduced retinal areas in the amblyopic eyes. Dysplastic and/or asymmetric optic discs were present in 163 of 293 (56 percent) amblyopic patients, 47 of 84 (56 percent) strabismic, and 10 of 77 (13 percent) normal patients.

CONCLUSIONS

The increase in the receptor area may be an explanation for diminished acuity and impaired visual function in amblyopic eyes.

Vision in children and adolescents with autistic spectrum disorder: evidence for reduced convergence

Evidence of atypical perception in individuals with ASD is mainly based on self report, parental questionnaires or psychophysical/cognitive paradigms. There have been relatively few attempts to establish whether binocular vision is enhanced, intact or abnormal in those with ASD. To address this, we screened visual function in 51 individuals with autistic spectrum disorder and 44 typically developing individuals by measuring visual acuity, stereoacuity, convergence, divergence, ocular motility, incidence of strabismus and integrity of the optokinetic response. The data suggest that many aspects of vision, including visual acuity, are unaffected in ASD, but that convergence is an aspect of visual function that merits further research in those with ASD.