A population-based study of ocular abnormalities in premature children aged 5 to 10 years

Characteristic differences between full-term and premature infants with intermittent exotropia

Strabismus is prevalent among preterm infants of low gestational age and birth weight in Southeast Asian countries, with intermittent exotropia (IXT) being the most common type in South Korea. In this retrospective, cross-sectional study, we investigated the differences between full-term and premature infants with IXT. IXT patients with available childbirth history were divided into two groups: preterm vs. full-term and low birth weight (LBW) vs. normal birth weight (NBW). Parameters related to exotropia including parental heredity, surgical history, and treatment options were investigated. In univariate regression for gestational age, a result of ≥ 100 s in the Titmus test was 1.352 times more frequent in preterm than in full-term infants. When birth weight was considered instead, a result of ≥ 100 s in the Titmus test was 1.412 times more frequent in the LBW compared to the NBW group. In multivariate regression for birth weight, the frequency of a result of ≥ 100 s in the Titmus test for the LBW group was 2.032 times higher than that for the NBW group. It is particularly important to examine stereopsis in preterm and LBW patients affected by IXT to ensure timely surgical planning and avoid potential recurrence after surgery.

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.

Longitudinal Change of Cup to Disc Ratio in Premature Infants with Enlarged Cup to Disc Ratio and Normal Intraocular Pressure

PURPOSE

To evaluate the longitudinal change of cup to disc ratio (CDR) in premature infants with enlarged CDR and normal intraocular pressure (IOP).

METHODS

This retrospective, observational study included 283 eyes of 283 premature infants at single center. Infants were divided into enlarged CDR and control groups. Data on demographics, gestational age (GA), birth weight (BW), vertical cup to disc ratio (vCDR), IOP, and corneal diameter were analyzed.

RESULTS

Of the 283 patients, 38 (13.4%) and 245 (86.6%) were in the enlarged CDR and control groups, respectively. In the enlarged CDR group, the vCDR and baseline IOP was 0.63 ± 0.12 and 12.7 ± 2.2 mmHg, respectively. In the control group, the vCDR and baseline IOP was 0.18 ± 0.05 and 10.9 ± 1.7 mmHg, respectively. The IOP at a GA of 40 weeks and at 1 and 2 years of age were significantly lower than that at baseline. The differences in vCDR between baseline and each follow-up visit were not significant. vCDR was negatively correlated with GA and BW; however, these correlations were not significant.

CONCLUSIONS

The vCDR did not significantly change up to age of 2 years of age in premature infants with enlarged CDR and normal IOP. However, close follow-up is needed until other reliable glaucoma examinations, such as optical coherence tomography and visual fields, can be possible.

Effects of prematurity and retinopathy of prematurity on refractive errors and biometric optic components in school children: results of a tertiary center from Turkey

PURPOSE

To reveal refractive errors, the relationship between refractive errors and optical parameters, and the effect of prematurity and retinopathy of prematurity (ROP) on ocular development in school children with a history of prematurity.

METHODS

Premature children aged 8-12 years were divided into 3 groups as those without ROP (Group 1), with ROP that did not require treatment (Group 2), and with laser-treated ROP (Group 3). Age-matched full-term healthy children were included in the control group. Demographic features were recorded. A detailed ophthalmologic examination was performed. Anterior chamber depth (ACD), trabecular-iris angle (TIA), iris thickness (IT), lens thickness (LT), vitreous body length (VBL), axial length (AL) were measured by ultrasound biomicroscopy (UBM). The results were compared between groups.

RESULTS

Group 3 had the lowest best corrected visual acuity (0.81 ± 0.31 SL), the highest rates of myopia (55.9%) and astigmatism (50.0%). In the premature groups, ACD (p < 0.001), TIA (p < 0.001), IT (p = 0.016), VBL (p < 0.001) and AL (p < 0.001) were lower; LT (p < 0.001) was higher than in the control group. As birth weight (BW) and gestational age (GA) increased, ACD, TIA, VBL and AL increased, and LT decreased (p < 0.001). In the group 3, 35.2% anisometropia, 17.6% of esotropia and 5.9% of exotropia were detected.

CONCLUSIONS

The frequency of myopia, astigmatism, hyperopia and anisometropia is increasing in premature children, especially in cases with laser-treated ROP. Premature cases are characterized by thicker lens, shallower ACD, narrower TIA and shorter AL. Refractive errors, anisometropia, amblyopia and strabismus are important causes of visual impairment in children with laser-treated ROP.

Functional Ophthalmic Factors Associated With Extreme Prematurity in Young Adults

IMPORTANCE

Children born preterm (<37 weeks' gestation) have a higher risk of visual impairment and ocular morbidities compared peers born at full term. However, the long-term ocular sequelae in adulthood for those born extremely preterm (EP), who have the highest risk of neonatal retinopathy, are unknown.

OBJECTIVE

To evaluate visual function and ocular morbidity in young adults born EP compared with controls born full term.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study of a geographically based birth cohort in the UK and Ireland born from March 1 through December 31, 1995, included 128 participants aged 19 years (born at 22-25 weeks' gestation) and 65 age-matched controls born at full term. Statistical analysis was performed from March 1, 2020, to November 26, 2021.

EXPOSURES

Participants underwent eye examinations as part of a comprehensive outcome evaluation.

MAIN OUTCOMES AND MEASURES

Best-corrected visual acuity, refractive status, contrast sensitivity, color vision, prevalence of strabismus and nystagmus, and patient-reported visual function, measured using the Health Utilities Index Mark 3.

RESULTS

The study comprised 128 participants (256 eyes; 68 female participants [53%]; mean [SD] age, 19.3 [0.5] years) and 65 age-matched controls born at full term (130 eyes; 40 female participants [62%]; mean [SD] age, 19.2 [0.5] years). Compared with control eyes, the mean (SD) best-corrected visual acuity among eyes in the EP group was significantly worse (monocular vision: -0.06 [0.14] logMAR in the control group vs 0.14 [0.38] logMAR in the EP group; P < .001; binocular vision: -0.14 [0.15] logMAR in the control group vs 0.06 [0.37] logMAR in the EP group; P < .001). Participants in the EP group had a significantly higher prevalence of strabismus (36% [46 of 127] vs 0%; P < .001), abnormal ocular motility (15% [19 of 125] vs 0%; P < .001), and nystagmus (13% [16 of 127] vs 0%; P < .001) than the control group. No significant differences between participants in the EP group and controls were observed for refractive error, contrast sensitivity, color vision, or patient-reported visual function. Among the participants in the EP group, 48% of eyes (120 of 250) had no retinopathy of prematurity (ROP), 39% (98 of 250) had ROP not requiring neonatal treatment, and 13% (32 of 250) received cryotherapy or laser ablation for ROP. Within the EP group, there was no significant difference in binocular visual function parameters, prevalence of ocular morbidity, and patient-reported visual function by neonatal ROP status.

CONCLUSIONS AND RELEVANCE

Extreme prematurity is associated with an increased prevalence of visual and ocular deficits in young adulthood; this study suggests that, for individuals born EP, visual and ocular deficits appear to be partially independent of ROP status in the neonatal period but reports similar overall visual function.

The Development of Ocular Biometric Parameters in Premature Infants without Retinopathy of Prematurity

PURPOSE

The aim of this study was to investigate the developmental tendencies and distribution of ocular biometric parameters in premature infants without retinopathy of prematurity (ROP). Axial length (AL), anterior chamber depth (ACD), lens thickness (LT) and vitreous length (VL) were measured, and their relationships with birth weight (BW) and postmenstrual age (PMA) were analyzed during their earliest weeks of life.

METHODS

This cross-sectional cohort study included 633 premature infants. They were divided into nine groups according to their PMA: 32 weeks, 33 weeks, 34 weeks, and onward to 40 weeks. All participants underwent portable slit-lamp examination, RetCam3 and A-scan ultrasound biometry. The following ocular biometric parameters were recorded: AL, ACD, LT and VL. The t-test, one-way analysis of variance, and the multiple regression analysis model were used to analyze the data.

RESULTS

The increases in AL, ACD, LT and VL were 0.14 mm, 0.028 mm, 0.0025 mm and 0.11 mm per week, respectively. AL, ACD, LT and VL were positively correlated with BW (β = 0.000337, 4.234E-5, 2.697E-5, 0.000278, respectively) and PMA (β = 0.142, 0.026, 0.011, 0.103, respectively).

CONCLUSIONS

With maturation, AL and VL increased and ACD deepened, but there was no significant change in LT. The ocular growth parameters were positively correlated with BW and PMA however the correlations were not strong.

An early phase of instructive plasticity before the typical onset of sensory experience

While early experience with moving stimuli is necessary for the development of direction selectivity in visual cortex of carnivores, it is unclear whether experience exerts a permissive or instructive influence. To test if the specific parameters of the experienced stimuli could instructively sculpt the emergent responses, visually naive ferrets were exposed to several hours of experience with unusual spatiotemporal patterns. In the most immature ferrets, cortical neurons developed selectivity to these patterns, indicating an instructive influence. In animals that were 1–10 days more mature, exposure to the same patterns led to a developmentally-typical increase in direction selectivity. We conclude that visual development progresses via an early phase of instructive plasticity, when the specific patterns of neural activity shape the specific parameters of the emerging response properties, followed by a late phase of permissive maturation, when sensory-driven activity merely serves to enhance the response properties already seeded in cortical circuits.

Brain circuits exhibit different amounts of plasticity over different developmental stages. Here authors show that there is a transition of the influence of spatiotemporal patterns, from instructive to permissive, around the time of the onset of visual experience.

A comparison of surgical outcomes between pre-and full-term patients with exotropia

PURPOSE

To compare the surgical outcomes between pre- and full-term patients with exotropia and to examine the factors associated with surgical outcomes.

METHODS

This retrospective study included 48 pre- and 432 full-term patients with basic-type exotropia who underwent unilateral or bilateral lateral rectus muscle (ULR or BLR) recession. Preoperative characteristics and surgical outcomes were compared between the pre- and full-term infants. Additionally, factors affecting the surgical outcomes were evaluated in all patients.

RESULTS

The preoperative characteristics were significantly different between the pre- and full-term groups in terms of neurodevelopmental disabilities (p = 0.020). There were no significant differences between the pre- and full-term groups in terms of the success, overcorrection, and recurrence rates after the mean follow-up period of 34.6 ± 13.9 months (p = 0.697). The major cause of surgical failure was recurrence in both groups. Pre-term birth was not a risk factor for overcorrection and recurrence. However, regardless of the pre- or full-term birth status, the presence of neurodevelopmental disabilities significantly affected final overcorrection (p = 0.004).

CONCLUSIONS

Pre-term patients with exotropia showed similar surgical outcomes to full-term controls. The presence of neurodevelopmental disabilities was a risk factor for final overcorrection.

Comparative study of visual dysfunctions in 6-10-year-old very preterm- and full-term-born children

PURPOSE

To compare visual dysfunction between very preterm-born (VPB) children with no retinopathy of prematurity (no-ROP) at 6-10 years of age and age- and sex-matched full-term-born controls.

METHODS

This is an observational, prospective study that included 30 children, 6-10 years of age, born ≤ 32 weeks of gestation, with no-ROP, and 30 age- and sex-matched full-term-born controls, conducted from January 2015 until August 2015. All children underwent complete ophthalmic evaluation. Main outcome measures include visual functions (best corrected visual acuity (BCVA), color vision, and stereoacuity), ocular alignment, refractive errors, and the presence of amblyopia and nystagmus.

RESULTS

Mean BCVA of the right eyes was 0.04 ± 0.08 logMAR for VPB children and 0.02 ± 0.05 logMAR for the full-term children (P = 0.075). Mean BCVA for the left eyes was 0.07 ± 0.09 logMAR for VPB children and 0.02 ± 0.05 logMAR for the full-term children (P = 0.014). Refractive errors were slightly higher though not statistically significant in VPB children compared to full-term children (P = 0.125). The incidence of myopia and hypermetropia was 16.7 and 40%, respectively, in VPB children and 10 and 23.3%, respectively, in full-term children. Anisometropia found only in VPB children with an incidence of 16.7%. Amblyopia found in 10% of VPB children compared to 3.3% in full-term children. Strabismus was found equally in 10% of each group.

CONCLUSION

VPB children with no-ROP are at an increased risk of developing decreased BCVA at least in one eye and anisometropia compared to age-matched full-term controls.

Prevalence and Risk Factors of Amblyopia among Refractive Errors in an Eastern European Population

Background and objective: Amblyopia is the leading cause of visual impairment in children and adults and is very common during childhood. The aim of this study was to identify the prevalence and the risk factors of amblyopia in a pediatric population with refractive errors from an Eastern European country. Materials and methods: A total of 1231 children aged 5–16 years, who had refractive errors and were examined from January to August 2017, were enrolled in a cross-sectional population-based study. Every child underwent a complete ophthalmological exam. Amblyopia was defined as a visual acuity (VA) of less than 0.63. The study respected the Multi-Ethnic Pediatric Eye Disease Study (MEPEDS) criteria for defining amblyopia (MEPEDS, 2008). Parents participated in a face-to-face interview. The questionnaire contained details about their family history of amblyopia; the child’s maternal nutritional status in the preconception period; their history of maternal smoking or work in a toxic environment; the child’s birth, and the child’s history of congenital naso-lacrimal duct obstruction (CNLDO). Results: Amblyopia was identified in 2.8% of the participants. The ocular conditions hyperopia (p = 0.0079), astigmatism (p = 0.046), anisometropia (p < 0.001), esotropia (p < 0.001), exotropia (p = 0.0195), and CNLDO (p < 0.001), as well as a family history of amblyopia (p < 0.001), were associated with amblyopia. The non-ocular risk factors for amblyopia that were found in the study included low birth weight (p < 0.0009), prematurity (p < 0.001), an Apgar score under 7 (p = 0.0008), maternal age, maternal smoking history or work in toxic environment (p < 0.001), and maternal body mass index in the preconception period (p < 0.003). Conclusions: Some of the risk factors we identified for amblyopia are modifiable factors. This is an important observation as an adequate health education program can provide the relevant information for future mothers that will allow for a better management of the condition. We also wanted to highlight the need for amblyopia screening starting from the age of 3 years in case of significant parental refractive errors, strabismus, prematurity, and maternal risk factors.

Prevalence and associated factors of strabismus in former preterm and full-term infants between 4 and 10 Years of age

Background

Limited data exist collating most of the associated factors for strabismus in one analysis. The aim of this study was to assess the prevalence of strabismus and to analyse associated factors in former preterm and full-term infants.

Methods

In this cross-sectional study, 239 former preterm infants with gestational age (GA) ≤ 32 weeks and 264 former full-term born infants with GA ≥ 37 weeks underwent detailed ophthalmologic examination in the age of 4–10 years and perinatal data assessment for risk factor analysis. Ophthalmologic examinations included cover testing, best corrected visual acuity, cycloplegic objective refraction, slit lamp as well as fundus examinations. For association analysis with strabismus, the following data was collected and included in multivariable analysis: sex, age at examination, anisometropia, myopic and hyperopic refractive error (≥ 3 dioptres), astigmatism, birth weight percentile, gestational age, retinopathy of prematurity occurrence, maternal age at childbirth, mother smoking, breastfeeding < 3 months, artificial ventilation, intraventricular bleeding, and other perinatal adverse events.

Results

Overall, 4/264 (2%) full-term infants, 15/125 (12%) preterm-infants with GA 29–32 weeks without ROP, 13/59 (22%) preterm infants with GA ≤ 28 weeks without ROP and 14/55 (26%) with GA ≤ 32 weeks with retinopathy of prematurity were affected by strabismus. In the multivariable regression model strabismus was associated with GA (OR = 0.84 per week; p = 0.001), hyperopic refractive error (OR = 4.22; p = 0.002) and astigmatism (OR = 1.68; p = 0.02).

Conclusion

This investigation highlights that low gestational age and refraction of the eye are independent risk factors for strabismus, while the other factors show less independent influence.

Long-term evaluation of refractive changes in eyes of preterm children: a 6-year follow-up study

PURPOSE

To investigate the longitudinal changes in refractive errors in preterm children with and without retinopathy of prematurity (ROP) in the first 6 years of life.

METHODS

We included 226 preterm children with a gestational age of ≤34 weeks: 222 eyes with no ROP, 73 eyes with mild ROP and 145 eyes with severe ROP. Longitudinal cycloplegic refraction data were collected initially and yearly thereafter until 6 years of age.

RESULTS

Eyes in the severe ROP group showed an increase in myopia values between the 1- and 3-year examinations (p = 0.005), with little change thereafter. However, the mild/no ROP group demonstrated a nonsignificant increasing myopia values throughout the 6-year follow-up (p = 0.073). Both the mild/no ROP and severe ROP groups were found to have increasing mean astigmatism values with increasing age, albeit nonsignificantly (p = 0.418, p = 0.384, respectively). Likewise, the stable mean values of anisometropia increased nonsignificantly during the first 6 years of life in both the mild/no ROP and severe ROP groups (p = 0.246, p = 0.073, respectively). Severe ROP group had higher values regarding myopia, astigmatism, and anisometropia parameters than the mild/no ROP group for all ages during the follow-up.

CONCLUSIONS

Preterm children with severe ROP should be closely monitored, and also those with mild/no ROP should be carefully followed up for not overlooking possible increases in refractive conditions.

Ophthalmological findings in relation to auxological data in moderate-to-late preterm preschool children

PURPOSE

To evaluate ophthalmological findings in preschool children born moderate-to- late preterm (MLP) and relate the findings to auxological data at birth and at 5.5 years of age.

METHODS

Seventy-eight MLP children [gestational age (GA) 32-36 weeks; 34 girls; mean age 5.7 years] were investigated. Gestational age, weight, length and head circumference at birth and at the time of assessment were registered. Visual acuity (VA), refraction, orthoptic evaluation, slit-lamp examination and ophthalmoscopy were conducted, and a history of visuoperceptual problems was recorded. The data were compared with age- and sex-matched controls born full term (n = 35).

RESULTS

Ophthalmological abnormalities were noted in 82% of MLP children and 47% of controls (p = 0.0004). There was a significant difference with regard to impaired motility (p = 0.03), heterophoria at distance (p = 0.006) and refraction expressed as spherical equivalent dioptre (p = 0.01). Amongst auxological data at birth, birthweight (BW) was the strongest predictor to ophthalmological abnormalities (p = 0.0003). In a stepwise logistic regression, GA was the strongest predictor of VA outcome at time of assessment (p = 0.0036). Moderate-to-late preterm birth showed a 2.4-fold increased risk of refractive errors compared with full-term children (RR 2.39: 95% CI 1.10-5.20; p = 0.02).

CONCLUSION

Based on our findings, MLP birth may be associated with increased ocular morbidity compared with their full-term counterparts. Auxological data at birth, especially BW, seems to be an important factor when conducting an ophthalmological diagnosis in preschool MLP children, and an increased VA was correlated to a higher GA.

Comparison of Retinal Nerve Fiber Layer Thickness in Terms of Birth Weight in Prematurely Born Children

PURPOSE

To study the potential effects of both prematurity and the sub-groups of low birth weight on thickness of RNFL.

METHODS

Prospective case series of 26 preterm school-aged children with low birth weight whose retinal nerve fiber layer analyses with RTVue-100 Fourier-domain optic coherence tomography were performed in 2013 at the Department of Ophthalmology, Erzurum Region Education and Training Hospital.

RESULTS

The mean retinal nerve fiber layer thicknesses were 100.6 ± 13.3 microns in extremely low birth weight, 103.9 ± 8.4 microns in very low birth weight, and 104.1 ± 10.8 microns in low birth weight groups. There was no significant difference in RNFL among the groups.

CONCLUSIONS

No significant relationship was found between birth weights and retinal nerve fiber layer thickness of preterm children who were appropriate for gestational age.

Sensory eye balance in surgically corrected intermittent exotropes with normal stereopsis

Surgery to align a deviated or strabismic eye is often done for both functional as well as cosmetic reasons. Although amblyopia is often an impediment to regaining full binocularity in strabismics in general, intermittent exotropes, because their deviation is intermittent, have no amblyopia and some degree of stereopsis. Binocular function, including a balanced ocular dominance, could be expected to be normal after surgical correction if normal levels of stereopsis and visual acuity are postsurgically achieved. Here we used a binocular phase combination paradigm to quantitatively assess the ocular dominance in a group of surgically corrected intermittent exotropes who have normal stereo and visual acuity as defined clinically. Interestingly, we found significant interocular imbalance (balance point < 0.9) in most of the surgically treated patients (8 out 10) but in none of the controls. We conclude that the two eyes may still have a residual sensory imbalance in surgically corrected strabismus even if stereopsis is within normal limits. Our study opens the possibility that a further treatment aimed at re-balancing the ocular dominance might be necessary in surgically treated intermittent exotropia to provide more efficient binocular processing in the long term.

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.

Scheimpflug imaging for long-term evaluation of optical components in Hungarian children with a history of preterm birth

PURPOSE

To determine ocular geometry and refraction in children with a history of preterm birth, and compare them to age-matched full-term children.

METHODS

In a prospective case-control study, 50 eyes of 27 premature patients 7 to 14 years of age were evaluated with Scheimpflug camera after cycloplegia. Age-matched full-term children comprised the control group (68 eyes of 34 children). All of the eligible eyes had a normal-appearing posterior pole. Anterior segment parameters such as keratometry, anterior chamber volume or thickness, and lens thickness were measured. Corneal thickness, lower- and higher-order aberrations refractive errors of the cornea (root mean square of lower- and higher-order aberrations: RMS LOA, RMS HOA) were also assessed and exported for further analysis.

RESULTS

In the premature eyes, anterior chamber depth was marginally smaller (P = .06), the lens was significantly thicker (P = .03), and axial length was significantly shorter (P < .001). Scheimpflug imaging showed a significant difference in corneal RMS (P = .03) and an increase in corneal RMS HOA (P = .002) in the premature group. Preterm birth showed significant impact on axial length (P < .01) and lens thickness (P = .05); at the same time, anterior chamber depth was more influenced by retinopathy of prematurity stage (P = .01). Laser treatment showed marginally significant impact (P = .06) on anterior chamber depth.

CONCLUSIONS

In premature eyes with or without mild retinopathy of prematurity, anterior segment anatomy is slightly different and they have more higher-order corneal aberrations compared to the eyes of term-born children.

Developmental changes in the balance of disparity, blur, and looming/proximity cues to drive ocular alignment and focus

Accurate coordination of accommodation and convergence is necessary to view near objects and develop fine motor coordination. We used a remote haploscopic videorefraction paradigm to measure longitudinal changes in simultaneous ocular accommodation and vergence to targets at different depths, and to all combinations of blur, binocular disparity, and change-in-size ('proximity') cues. Infants were followed longitudinally and compared with older children and young adults, with the prediction that sensitivity to different cues would change during development. Mean infant responses to the most naturalistic condition were similar to those of adults from 6-7 weeks (accommodation) and 8-9 weeks (vergence). Proximity cues influenced responses most in infants of less than 14 weeks of age, but sensitivity declined thereafter. Between 12 and 28 weeks of age infants were equally responsive to all three cues, while in older children and adults manipulation of disparity resulted in the greatest changes in response. Despite rapid development of visual acuity (thus increasing availability of blur cues), responses to blur were stable throughout development. Our results suggest that, during much of infancy, vergence and accommodation responses are not dependent on the development of specific depth cues, but make use of any cues available to drive appropriate changes in response.

Factors associated with strabismus in spina bifida myelomeningocele

PURPOSE

Higher prevalence of strabismus in individuals with spina bifida myelomeningocele (SBM) has previously been attributed to hydrocephalus; however, SBM is associated with many other complications. This study investigates the relation between strabismus and other factors in SBM.

METHODS

Children aged 3 to 18 years with SBM (n = 112) received an eye examination including assessment of ocular alignment by cover or Hirschberg test. Gestational age, respiratory distress at birth, birth weight, maternal age at birth, number of shunt revisions, and spinal lesion level were also obtained. The relation between these factors and strabismus was analyzed.

RESULTS

Forty-two participants had strabismus. Maternal age (P = .4) and respiratory distress (P = .6) were not significantly related to strabismus. Lower birth weight was suggestive of a relation with strabismus (logistic regression, P = .05) and younger gestational age was related to strabismus (logistic regression, P = .01). Participants who had at least one shunt revision were more likely to have strabismus (Fisher's exact test, P = .038). Spinal lesion level was significantly related to strabismus with increased likelihood of strabismus for spinal lesions closer to the brain (Wald chi-square, 1,100 = 4.29, P = .038).

CONCLUSION

These findings indicate that several factors are associated with strabismus in SBM. Some of these factors (lower birth weight and younger gestational age) are associated with strabismus in the general population, whereas the association of strabismus and level of spinal lesion may be unique to SBM and may be related to the more severe brain dysmorphology associated with upper level spinal lesions.

An assessment of ocular morbidities of children born prematurely in early childhood

PURPOSE

To assess the ocular morbidities of premature children in early childhood.

METHODS

One hundred seventeen children with a history of gestational age of less than 37 weeks at birth underwent ophthalmic examination including visual acuity testing with Lea symbols, anterior and posterior segment examination, refraction, orthoptic examination for strabismus, and ocular biometry. They were subdivided into three groups according to gestational age (28 or less, 29 to 32, and 33 to 36 weeks). The prevalence of ocular morbidities and mean value of refractive errors were studied.

RESULTS

The mean age of the subjects at examination was 37.6 ± 1.1 months (range: 20 to 65 months). Only 62.4% of the eyes had visual acuity better than 20/32. The prevalence of high myopia (above -5.0 diopters [D]), myopia (below -5.0 D), and strabismus was 12.5%, 22.5% and 33.3% in the 28 weeks or less group and 3.6%, 18.9%, and 24.1% in the 29 to 32 weeks group, respectively, whereas 7.9% of the 33 to 36 weeks group had myopia and 13.2% had strabismus. Spherical equivalent in eyes that received cryotherapy and with macular heterotopia was -2.7 ± 3.9 and - 4.4 ± 3.4 D, respectively. Biometric measurements showed that high myopic eyes had statistically significantly thicker lenses compared to myopic and hyperopic eyes (P = .01).

CONCLUSION

This study confirms that children born prematurely are at increased risk of ocular morbidities such as defective visual acuity, myopia, and strabismus. High myopic eyes have thicker lenses compared to myopic and hyperopic eyes, and eyes with macular heterotropia and treated with cryotherapy are more prone to development of high myopia.

Characteristics of peripapillary retinal nerve fiber layer in preterm children

PURPOSE

To examine quantitatively characteristics of the peripapillary retinal nerve fiber layer (RNFL) in preterm children using Fourier-domain optical coherence tomography (FD-OCT).

DESIGN

Prospective cross-sectional study.

METHODS

A 3-mm high-resolution FD-OCT peripapillary RNFL circular scan centered on the optic disc was obtained from right eyes of 25 preterm children (10.6 ± 3.7 years old, 8 preterm and 17 with regressed retinopathy of prematurity with normal-appearing posterior poles) and 54 full-term controls (9.8 ± 3.2 years old). Images were analyzed using Spectralis FD-OCT software to obtain average thickness measurements for 6 sectors (temporal superior, temporal, temporal inferior, nasal inferior, nasal, nasal superior), and the global average.

RESULTS

The RNFL global average for preterm children was 8% thinner than for full-term controls. In the preterm group, peripapillary RNFL thickness on the temporal side of the disc was 6% thicker than in full-term controls, while all other peripapillary RNFL sectors were 9% to 13% thinner. In the preterm group, temporal sector peripapillary RNFL thickness was correlated with gestational age (r = -0.47, P < .001), with foveal center total thickness (r = 0.48, P = .008, 1-tailed), and with visual acuity (r = 0.42; P = .026, 1-tailed).

CONCLUSIONS

The significantly thinner RNFL global average for preterm children suggests that prematurity is associated with subclinical optic nerve hypoplasia. Significant correlations between temporal sector RNFL thickness and both the foveal thickness and visual acuity suggest that the peripapillary RNFL is related to abnormalities in macular development as a result of preterm birth.

Risk factors associated with childhood strabismus: the multi-ethnic pediatric eye disease and Baltimore pediatric eye disease studies

OBJECTIVE

To investigate risk factors associated with esotropia or exotropia in infants and young children.

DESIGN

Population-based cross-sectional prevalence study.

PARTICIPANTS

Population-based samples of 9970 children 6 to 72 months of age from California and Maryland.

METHODS

Participants were preschool African-American, Hispanic, and non-Hispanic white children participating in the Multi-Ethnic Pediatric Eye Disease Study and the Baltimore Eye Disease Study. Data were obtained by parental interview and ocular examination. Odd ratios and 95% confidence intervals were calculated to evaluate the association of demographic, behavioral, and clinical risk factors with esotropia and exotropia.

MAIN OUTCOME MEASURES

Odds ratios (ORs) for various risk factors associated with esotropia or exotropia diagnosis based on cover testing.

RESULTS

In multivariate logistic regression analysis, esotropia was associated independently with prematurity, maternal smoking during pregnancy, older preschool age (48-72 months), anisometropia, and hyperopia. There was a severity-dependent association of hyperopia with the prevalence of esotropia, with ORs increasing from 6.4 for 2.00 diopters (D) to less than 3.00 D of hyperopia, to 122.0 for 5.00 D or more of hyperopia. Exotropia was associated with prematurity, maternal smoking during pregnancy, family history of strabismus, female sex, astigmatism (OR, 2.5 for 1.50 to <2.50 D of astigmatism, and 5.9 for ≥2.5 D of astigmatism), and anisoastigmatism in the J0 component (OR, ≥2 for J0 anisoastigmatism of ≥0.25 D).

CONCLUSIONS

Prematurity and maternal smoking during pregnancy are associated with a higher risk of having esotropia and exotropia. Refractive error is associated in a severity-dependent manner to the prevalence of esotropia and exotropia. Because refractive error is correctable, these risk associations should be considered when developing guidelines for the screening and management of refractive error in infants and young children.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

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.

An analysis of neonatal risk factors associated with the development of ophthalmologic problems at infancy and early childhood: a study of premature infants born at or before 32 weeks of gestation

BACKGROUND

To determine the frequency of ophthalmologic problems and the risk factors that affect the occurrence of these problems in premature newborns with a gestational age of 32 weeks or less.

METHODS

Premature newborns observed at a neonatal intensive care unit between January 2002 and March 2006 were included. A control visit including an ophthalmologic examination was performed at 10 months of age or later. Primary ocular morbidities were studied, and the association between these parameters and prenatal, perinatal, and neonatal characteristics were evaluated.

RESULTS

A total of 169 premature newborns were included in the study, and they were examined at a mean age of 25.85 ± 11.79 months (range: 10 to 42 months). There was complete vision loss (blindness) in 1 (0.6%) case, strabismus in 15 (8.9%) cases, and refractive errors in 10 (5.9%) cases. Twenty (77%) cases with any abnormality and 50 (35%) cases with a normal examination at follow-up had a history of retinopathy of prematurity (ROP) at any stage during the neonatal period (P = .001). Short gestational age (P = .018), low birth weight (P = .002), and the presence of ROP requiring retinal surgery during the neonatal period (P = .007) were determined to be significant risk factors for the development of vision loss, strabismus, and refractive errors.

CONCLUSION

Neonates with a gestational age of 32 weeks or less, especially those younger than 30 weeks, should not only be screened for ROP in the neonatal period, but should also have regular follow-up examinations to check for the development of other ophthalmologic problems during infancy and early childhood.

Ocular growth and morbidity in preterm children without retinopathy of prematurity

PURPOSE

To investigate ocular growth and morbidity in both preschool and school-aged children born prematurely without retinopathy of prematurity (ROP).

METHODS

This population-based study was carried out in 26 children, 5-7 years of age, born prematurely without ROP. All children underwent a full ocular examination, including corrected visual acuity, cycloplegic refractive errors, color vision, ocular alignment, and anterior and posterior segment examinations. Anterior chamber depth, lens thickness, vitreous length, and total axial length were measured.

RESULTS

There was no correlation between the degree of prematurity and visual acuity or refractive state. Two (7.7%) subjects had strabismus, two (7.7%) had amblyopia, and four (15%) had anisometropia. Total axial length was significantly correlated with both gestational age at birth (r=0.822, P<0.001) and birth weight (r=0.569, P=0.003). Similarly, vitreous length was also significantly correlated with gestational age (r=0.744, P<0.001) and birth weight (r=0.553, P=0.004).

CONCLUSIONS

This study showed that although the globe gets longer as gestational age approaches term and as birth weight increases, this condition does not result in any significant refractive error. According to the literature, the prevalence of strabismus, amblyopia, and anisometropia may be higher in preterm children without ROP than in age-matched, normally delivered children.

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.

Severe retinopathy of prematurity and visual outcomes in British Columbia: a 10-year analysis

OBJECTIVE

To describe the incidence trend and long-term visual outcomes of infants diagnosed with stages 3 to 4 retinopathy of prematurity (ROP) or laser-treated ROP born in British Columbia (Canada).

STUDY DESIGN

Data from all (n=1384) neonates with birth weight (BW) <1250 g, admitted to British Columbia Children's Hospital between period 1 (January 1992 to December 1996) and period 2 (January 1997 to December 2001) were analyzed. Ophthalmologic records of infants with stages 3 to 4 ROP or laser-treated ROP were abstracted. chi(2)- and t-test were used to compare neonatal characteristics between periods. Logistic regression was used to identify risk factors associated with visual impairment (defined as visual acuity <or=20/60 or visual field restriction of 20 degrees binocularly).

RESULT

Of 1159 surviving infants, 887 were examined for acute ROP (473 in period 1, 414 in period 2). Stages 3 to 4 ROP or laser-treated ROP were present in 35 infants in period 1 (7%) and 59 in period 2 (14%), P<or=0001. Infants born in period 2 had lower mean BW and gestational age. Among infants who developed severe ROP or laser-treated ROP, binocular visual impairment was present in eight children in period 1 and seven in period 2. Refractive errors, including myopia and astigmatism, were increased in period 2. Children who developed periventricular leucomalacia had the highest risk of visual impairment at 4 to 6 years of age.

CONCLUSION

During the 10-year study period, a significant increase in rates of stages 3 to 4 or laser-treated ROP was not associated with increases in visual impairment rates.

Progression of myopia and high myopia in the early treatment for retinopathy of prematurity study: findings to 3 years of age

PURPOSE

Examine the prevalence of myopia and high myopia, at 6 and 9 months postterm and 2 and 3 years postnatal in preterm children with birth weights < 1251 g who developed high-risk prethreshold retinopathy of prematurity (ROP) in the neonatal period and participated in the Early Treatment for ROP Study.

DESIGN

Randomized controlled clinical trial.

PARTICIPANTS

Four hundred one infants who developed prethreshold ROP and were determined to have a significant risk (>/=15%) of poor structural outcomes without treatment. Children underwent cycloplegic retinoscopy at examinations between 6 months postterm and 3 years' postnatal age.

INTERVENTION

Eyes were randomized to receive treatment at high-risk prethreshold ROP (early treated [ET]) or conventional management (CM), with treatment only if threshold ROP developed.

MAIN OUTCOME MEASURES

Myopia (spherical equivalent >/= 0.25 diopters [D]) or high myopia (>/=5.00 D) at each visit.

RESULTS

Prevalences of myopia were similar in treated eyes in the ET and CM groups, increasing from approximately 58% to 68% between 6 and 9 months, with little change thereafter. Both ET and CM eyes showed an increasing prevalence of high myopia, approximately 19% at 6 months and increasing 4% to 8% at successive examinations. Zone of ROP and presence or absence of plus disease had little effect on prevalence of myopia or high myopia between ages 6 months and 3 years. However, eyes with ROP residua (straightened temporal vessels or macular heterotopia) showed a higher prevalence of myopia and high myopia than eyes without residua.

CONCLUSIONS

Approximately 70% of high-risk prethreshold ROP eyes were myopic in early childhood, and the proportion with high myopia increased steadily between ages 6 months and 3 years. Timing of treatment of high-risk prethreshold ROP did not influence refractive error development. There was little difference in prevalence of myopia or high myopia between eyes with zone I and eyes with zone II ROP, nor between eyes with plus disease and eyes with no plus disease. However, prevalence of myopia and high myopia was higher in eyes with retinal residua of ROP than in eyes with normal-appearing posterior poles, highlighting the importance of follow-up eye examinations of infants who had prethreshold ROP.

Eye movements and binocular function in low birthweight teenagers

PURPOSE

To assess eye movements and binocular function in 14-year-olds with very low birthweight (VLBW: birthweight </= 1500 g) and 14-year-olds born at term but small for gestational age (SGA: birthweight < 10th percentile) in a population-based study.

METHODS

Ophthalmological examinations including measurements of heterophoria/tropia, near point of convergence, accommodative amplitude, stereopsis, nystagmus, saccades and smooth pursuit were performed in 51 adolescents with VLBW, 58 adolescents born SGA and in a control group consisting of 75 subjects of the same age.

RESULTS

Latent or manifest strabismus, poor stereopsis, poor convergence and nystagmus were all more frequent in the VLBW group than in the control group. The VLBW group did not differ from the control group regarding accommodative amplitude or saccades and smooth pursuit. The SGA population did not differ from the control group in the measured variables.

CONCLUSIONS

Premature birth with VLBW affects binocular visual functions negatively in adolescence, whereas birth small for date at term does not appear to be a risk factor for impaired eye movements and binocular function.

Prevalence and development of strabismus in 10-year-old premature children: a population-based study

PURPOSE

To evaluate the prevalence and development of strabismus, at 10 years, in children born prematurely.

METHODS

This population-based study included 216 premature and 217 full-term children from the same geographic area.

RESULTS

Strabismus was noted in 16.2% (35 of 216) premature and in 3.2% (7 of 217) full-term children. The most important risk factors for strabismus at 10 years were anisometropia at 6 months, spherical equivalent refractive errors (i.e., > +3 D or < -3 D) at 2.5 years, and various neurologic conditions.

CONCLUSION

At 10 years, children born prematurely have a greater risk of strabismus than children born at term.

Prevalence and associations of anisometropia and aniso-astigmatism in a population based sample of 6 year old children

AIM

To study the distribution of anisometropia and aniso-astigmatism in young Australian children, together with clinical and ocular biometry relations.

METHOD

The Sydney Myopia Study examined 1765 predominantly 6 year old children from 34 randomly selected Sydney schools during 2003-4. Keratometry, cycloplegic autorefraction, and questionnaire data were collected.

RESULTS

Spherical equivalent (SE) anisometropia (> or =1 dioptre) prevalence was 1.6% (95% confidence interval (CI) 1.1% to 2.4%). Aniso-astigmatism (>or =1D) prevalence was 1.0% (CI: 0.6% to 1.6%). Both conditions were significantly more prevalent among moderately hyperopic (SE > or =2.0D) than mildly hyperopic (SE 0.5-1.9D) children. Myopic children (SE < or =-0.5D) had higher anisometropia prevalence. Neither condition varied by age, sex, or ethnicity. In multivariate analyses, anisometropia was significantly associated with amblyopia, odds ratio (OR) 29, (CI: 8.7 to 99), exotropia (OR 7.7, CI: 1.2 to 50), and neonatal intensive care unit (NICU) admission (OR 3.6, CI: 1.1 to 12.6). Aniso-astigmatism was significantly associated with amblyopia (OR 8.2, CI: 1.4 to 47), maternal age >35 years (OR 4.0, CI: 1.3 to 11.9), and NICU admission (OR 4.6, CI: 1.2 to 17.2). Anisometropia resulted from relatively large interocular differences in axial length (p<0.0001) and anterior chamber depth (p = 0.0009). Aniso-astigmatism resulted from differences in corneal astigmatism (p<0.0001).

CONCLUSION

In this predominantly 6 year old population, anisometropia and aniso-astigmatism were uncommon, had important birth and biometry associations, and were strongly related to amblyopia and strabismus.

Contrast sensitivity in 10 year old preterm and full term children: a population based study

AIMS

To determine the contrast sensitivity (CS) in 10 year old prematurely born children, previously included in a population based study on the incidence of retinopathy of prematurity (ROP), and in full term controls.

METHODS

This study included 205 prematurely born children and 215 children born at term, from the same geographical area and study period. CS was assessed monocularly with the Vistech 6500 test at five spatial frequencies (1.5-18 cycles/deg).

RESULTS

Prematurely born children had statistically significant lower CS at all frequencies, compared to full term ones. The mean differences in logarithmic CS were 0.03 (1.5 cycles/deg), 0.09 (3 cycles/deg), 0.10 (6 cycles/deg), 0.12 (12 cycles/deg), and 0.19 (18 cycles/deg). Even when the children with ROP and neurological disorders were excluded there was a difference between the two groups. Children who had been treated with cryotherapy had the lowest CS.

CONCLUSION

CS was lower in 10 year old prematurely born children than in full term ones of the same age. Whether this finding affects their visual function in daily life is uncertain.

Prevalence of myopia at 9 months in infants with high-risk prethreshold retinopathy of prematurity

PURPOSE

To examine the prevalence of myopia and high myopia at 9 months corrected age in premature infants who participated in the multicenter randomized trial of Early Treatment for Retinopathy of Prematurity (ETROP).

DESIGN

Randomized, controlled clinical trial.

PARTICIPANTS

Four hundred one infants with birth weights of <1251 g in whom prethreshold ROP developed in one or both eyes and who were determined to have a significant risk (> or =15%) of poor structural outcomes without treatment, based on the risk management for ROP program.

INTERVENTION

Infants with bilateral high-risk prethreshold ROP (n = 317) had 1 eye randomized to early treatment, and the fellow eye was managed conventionally. In asymmetric cases (n = 84), the eye with high-risk prethreshold ROP was randomized to early treatment or conventional management (control). Eyes randomized to early treatment at high-risk prethreshold ROP and eyes randomized to conventional management in which threshold ROP developed received peripheral retinal photocoagulation or cryotherapy. Conventionally managed eyes in which threshold ROP did not develop were observed. Cycloplegic retinoscopy data were obtained at 9 months corrected age from 321 eyes treated early and 307 eyes managed conventionally.

MAIN OUTCOME MEASURES

Prevalence of myopic (spherical equivalent > or = 0.25 diopters [D]) and highly myopic (> or =5.00 D) eyes in each group.

RESULTS

The prevalence of myopia (64.5% vs. 69.4%; P = 0.06) and high myopia (25.5% vs. 28.3%; P = 0.20) was similar between eyes treated at high-risk prethreshold and high-risk prethreshold eyes managed conventionally. Among high-risk eyes managed conventionally, the prevalence of myopia (78.2% vs. 53.3%) and high myopia (37.6% vs. 11.2%) was higher when threshold ROP developed than when regression without treatment occurred. Among eyes treated at high-risk prethreshold ROP, the prevalence of myopia (93.3% vs. 91.7% vs. 60.6%) and of high myopia (53.3% vs. 33.3% vs. 20.8%) was higher in eyes with abnormal angle of temporal retinal vessels or macular ectopia than in eyes with no retinal residua. This also held true for conventionally managed eyes.

CONCLUSIONS

Early treatment at high-risk prethreshold did not place eyes at greater risk of myopia and high myopia than did conventional management of eyes with high-risk prethreshold ROP.

An analysis of high myopia in a pediatric population less than 10 years of age

PURPOSE

The purpose of this article is to document a comprehensive clinical profile-including the prevalence of amblyopia, strabismus, and anisometropia-of a pediatric population less than 10 years of age who manifested 6.00 diopters or more of myopia.

METHOD

A retrospective record review was performed on all pediatric patients less than 10 years of age, examined at the State University of New York (SUNY) State College of Optometry between 1998 and 2001, and with a spherical equivalent of 6.00 diopters or more of myopia.

RESULTS

One hundred seventy-eight patients met the criteria. Amblyopia or reduced corrected visual acuity was present in 75.8% of the patients. Strabismus was present in 31.5% of the patients, with essentially equal numbers of esotropes and exotropes. Anisometropia was present in 35.4% of the patients. One hundred forty-five patients had high myopia in the absence of significant ocular or systemic compromising conditions. In this sample of 145, strabismus or anisometropia was an etiology for amblyopia. There was a greater prevalence of bilateral high myopia (64.8%) than unilateral high myopia. Anisometropia was present in 10.6% of the bilateral high myopes, and 78.4% of the unilateral high myopes.

CONCLUSION

Children less than 10 years of age with high myopia have a high risk of having amblyopia, strabismus, and anisometropia.

Visual function in low birthweight children

AIM

To determine the visual functions, at age 10-12 years, of a geographically based cohort of children of birth weight less than 1701 g. The results were compared to a group of children born at full term.

METHODS

572 low birthweight (LBW) "low birthweight cohort" children who had been examined in the neonatal period were invited for review at 10-12 years of age. 169 11 year old schoolchildren born at full term were also recruited, "school cohort." Visual acuity (at distance and near), contrast sensitivity, colour vision, and visual fields were measured.

RESULTS

293 of the original 572 participants consented to a further examination. Compared to the school cohort of children born at term the low birthweight cohort showed significantly lower near and distance acuities and contrast sensitivity (p<0.001 for all uniocular and binocular measures). Retinopathy of prematurity (ROP) was a very poor predictor of outcome and multivariate analysis did not identify any key neonatal factors as predictors of long term visual outcome.

CONCLUSIONS

Low birthweight children have a small but statistically significant deficit in both visual acuity and contrast sensitivity. Low birth weight and ROP both impact on long term visual functions.

Refraction and keratometry in 40 week old premature (corrected age) and term infants

AIM

To compare refraction and keratometry readings between premature and term babies at 40 weeks' postconceptional age (PCA), and the possible effect of birth weight (BW) and gestational age (GA) on ocular parameters.

METHODS

33 preterm babies hospitalised in the neonatal unit between January and March 2002 were matched with 33 term babies born within the same period and hospitalised in the same unit. The preterm group underwent funduscopy at 4-5 weeks after delivery. Ophthalmic examination at 40 weeks' PCA included cycloplegic retinoscopy, funduscopy, and keratometric measurements. Mean and standard deviation of refraction, astigmatic power (plus cylinder), axis of astigmatism, and keratometric reading were calculated and compared between groups and correlated with BW and GA in the premature babies.

RESULTS

Retinopathy of prematurity (ROP) stage 1 or 2 was noted in 88% of the premature babies on the first funduscopy examination, but only in 36% by the corrected age of 40 weeks. Statistically significant between groups differences were found for cycloplegic refraction (p = 0.02 for both eyes) and keratometry (p = 0.001 for both eyes). GA and BW had no impact on the refractive and keratometric findings in the preterm babies.

CONCLUSIONS

Babies with mild ROP at the corrected age of 40 weeks have mild hypermetropia compared to the moderate hypermetropia found in term babies (a difference of 50%), and they have higher and steeper keratometric values. The greater corneal curvature may contribute to the development of myopia. Ophthalmologists and parents need to be aware of the possibility of visual dysfunction already very early in life even in relatively older premature infants.

Monocular chromatic contrast threshold and achromatic contrast sensitivity in children born prematurely

PURPOSE

To study the effect of prematurity on monocular chromatic contrast thresholds (CCT) and achromatic contrast sensitivity (ACS).

DESIGN

Case-control study.

METHODS

A prospective study of 59 children born at less than 33 weeks' gestation was undertaken. Subjects were identified during routine neonatal screening for retinopathy of prematurity and recalled for testing at age 7 to 13 years. Five had stage 1 retinopathy of prematurity, seven had stage 2, and three had stage 3. Sixty-eight full-term children were recruited as controls. Those with major cerebral or eye disease were excluded. The CCT and ACS were measured monocularly in the eye with better visual acuity using static, computer-generated, sinusoidal gratings, displayed on a high-resolution monitor. The CCT and ACS were determined using a randomized double-staircase reversal algorithm. The ACS was measured at five spatial frequencies (0.22, 0.44, 0.88, 1.75, and 3.50 cycles/degree), and the CCT was measured along red-green and tritan confusion axes.

RESULTS

Red-green (P =.326) and tritan (P =.910) contrast thresholds and ACS (P >.394 for all spatial frequencies) were similar to the control group.

CONCLUSIONS

Previous research suggests that prematurity adversely affects color vision and ACS. This study used a computerized psychophysical test that minimized the test errors inherent in many previous studies. Unexpectedly, CCT and ACS were found to be similar to full-term children.

Emmetropisation following preterm birth

BACKGROUND/AIMS

Even in the absence of retinopathy of prematurity (ROP), premature birth signals increased risk for abnormal refractive development. The present study examined the relation between clinical risk factors and refractive development among preterm infants without ROP.

METHODS

Cycloplegic refraction was measured at birth, term, 6, 12, and 48 months corrected age in a cohort of 59 preterm infants. Detailed perinatal history and cranial ultrasound data were collected. 40 full term (plus or minus 2 weeks) subjects were tested at birth, 6, and 12 months old.

RESULTS

Myopia and anisometropia were associated with prematurity (p<0.05). More variation in astigmatic axis was found among preterm infants (p<0.05) and a trend for more astigmatism (p<0.1). Emmetropisation occurred in the preterm infants so that at term age they did not differ from the fullterm group in astigmatism or anisometropia. However, preterm infants remained more myopic (less hyperopic) than the fullterm group at term (p<0.05) and those infants born <1500 g remained more anisometropic than their peers until 6 months (p<0.05). Infants with abnormal cranial ultrasound were at risk for higher hyperopia (p<0.05). Other clinical risk factors were not associated with differences in refractive development. At 4 years of age 19% of the preterm group had clinically significant refractive errors.

CONCLUSION

Preterm infants without ROP had high rates of refractive error. The early emmetropisation process differed from that of the fullterm group but neither clinical risk factors nor measures of early refractive error were predictive of refractive outcome at 4 years.

Preterm birth and visual development

Visual impairment, oculomotor abnormalities, and refractive error are prevalent among children with a history of preterm birth. These conditions may result from exposure of the immature visual system to early visual stimulation, from nutritional deficits that occur following the abrupt loss of placental maternal-to-fetal transfer of essential nutrients, and as secondary effects of systemic disease or complications associated with preterm birth. This chapter provides an overview of the structural and functional maturation of the visual system of the healthy preterm infant and of several forms of visual impairment that are prevalent in the low birth weight population.

The long term ophthalmic morbidity of low birth weight children: a review

Low birth weight infants are at greater risk of ophthalmic morbidity compared to children born at term. There are numerous studies detailing the outcome of low birth weight infants and the purpose of this paper is to discuss and summarize these studies, focusing on the long term effects on visual function and the prevalence of strabismus. The variation in study design will be discussed with regard to the subsequent effect on results. Despite the significant variation between studies, they all report an increase in the prevalence of strabismus and reduced visual acuity. This increase in ophthalmic morbidity is due in part to retinopathy of prematurity (ROP), but not all ophthalmic morbidity can be attributed to ROP.

Comitant strabismus

A review of the literature on comitant strabismus of the period from April 1999 until April 2000 is presented. A rather new and increasingly important issue is the psychosocial aspect of strabismus. Two studies have demonstrated that strabismus creates a significant negative social prejudice on the patients and that it can significantly reduce an applicant's ability to obtain employment. Subsequently, strabismus surgery can no longer be called "cosmetic". Concerning the timing of surgery in congenital esotropia, it was reported that early surgery does not ensure continued alignment, but frequently requires additional operations. The increased risk of early-onset strabismus in prematurely born children was confirmed by several studies, and the importance of regular ophthalmologic controls of all preterm infants screened for retinopathy of prematurity was stressed. It was reported that risk factors are cicatricial retinopathy of prematurity, refractive error, family history of strabismus, and poor neurodevelopmental outcome, rather than low gestational age and regressed acute retinopathy of prematurity. A number of other aspects of interest concerning exotropia, esotropia, and dissociated vertical deviation are presented in this review.

Screening for amblyogenic factors using a volunteer lay network and the MTI photoscreener. Initial results from 15,000 preschool children in a statewide effort

PURPOSE

To describe the results from a statewide preschool vision screening program using the MTI PhotoScreener (Medical Technology and Innovations, Inc., Cedar Falls, IA).

DESIGN

Cross-sectional study.

PARTICIPANTS

A total of 15,059 children aged 6 to 47 months enrolled in childcare and preschool settings throughout the state of Tennessee.

METHODS

Volunteers from local Lions Clubs took photoscreening photographs of children in a statewide effort. Photographs were interpreted at the Vanderbilt Ophthalmic Photography Reading Center using predetermined criteria. Children who failed the screening were referred to community ophthalmologists or optometrists who performed a comprehensive evaluation and forwarded the results to the authors.

MAIN OUTCOME MEASURES

Referral rate, unreadable rate, and predictive value positive (PVP).

RESULTS

During the 2 years of the screening program, 15,059 children were screened in 850 screenings. The screening referred 1013 children (6.7%), and 704 photographs (4.7%) were unreadable. Children who failed the screening had a significant abnormality (strabismus, anisometropia, high hypermetropia, high astigmatism, or high myopia) in 320 of the 531 cases where adequate follow-up results were reported. The PVP ranged from 84% when a diagnosis of strabismus was suggested by the photoscreen reading to 41% for astigmatism. Despite intense attention to follow-up, many children who failed the screening never received a formal eye examination.

CONCLUSIONS

The MTI PhotoScreener can be used by volunteers to screen preschool children and can have a high PVP in organized settings, provided that meticulous attention is paid to photograph interpretation and quality control. The PVP of the MTI PhotoScreener depends on the diagnosis suggested when the photograph is read. Significant obstacles exist in obtaining care for those who fail screening.

Long term refractive outcome in eyes of preterm infants with and without retinopathy of prematurity: comparison of keratometric value, axial length, anterior chamber depth, and lens thickness

BACKGROUND/AIMS

A longitudinal study of premature infants was conducted to examine changes in refractive status and their relation with age and factors influencing the occurrence and degree of myopia. Identification of which of the various refractive factors play important parts in relation to myopia in premature infants was attempted.

METHODS

Under observation were 125 eyes in 65 patients who were found to demonstrate no signs of retinopathy of prematurity (ROP) or who had grade I or II ROP without or after cryotherapy. Cycloplegic refractions were conducted at 6 months, 3 years, and 6 years of age; at 6 years of age keratometric values, lens thicknesses, and axial lengths were recorded, and anterior chamber depths also were measured.

RESULTS

Myopia begins to appear at 6 months of age and its severity increases between the ages of 6 months and 3 years. The condition showed no further progress in subjects older than 3 years. Of the 104 eyes with ROP, those eyes with cicatricial retinopathy tended towards myopia and high myopia while there was no difference in the degree of myopia related to whether or not cryotherapy was conducted. At 6 years of age, the premature infants exhibited shallower anterior chambers, thicker lenses, and higher axial lengths when the degree of the myopia was higher. The keratometric values, however, appeared to bear no relation to the degree of the myopia.

CONCLUSION

These results suggest that the occurrence of myopia is related more strongly to whether or not there is cicatricial retinopathy than whether or not there is cryotherapy. Also, the degree of the myopia was found to be related to the depth of the anterior chamber, the thickness of the lens, and the change in axial length but not to keratometric value.

Optic nerve morphology may reveal adverse events during prenatal and perinatal life--digital image analysis

OBJECTIVE

To evaluate optic nerve morphology in children with various conditions caused by adverse events during prenatal and/or perinatal life and to investigate whether optic nerve morphology can reveal brain lesions associated with these conditions, as well as provide insight into the etiology and timing of the prenatal and perinatal damage.

METHODS AND PATIENTS

A digital image analysis technique was used to analyze fundus photographs. One hundred healthy Swedish individuals of various ages from childhood to adolescence constituted a reference group. The following patient groups were chosen to represent various clinical conditions affecting the newborn or fetus at different stages of development: children born preterm (N = 39), children with fetal alcohol syndrome (FAS [N = 16]), children with periventricular leukomalacia (PVL [N = 17]), and children with septo-optic dysplasia (SOD [N = 6]).

RESULTS

Preterm children without known brain lesions demonstrated normal optic disk morphology but abnormal retinal vascular pattern; children born preterm with an acquired brain lesion late in gestation (PVL) demonstrated normal disk size with enlarged cups in addition to the abnormal vascular pattern. Children with prenatal alcohol exposure (FAS) had a subnormal optic disk area with increased tortuosity of both arteries and veins, whereas children born at term with an early acquired brain lesion (SOD) had a markedly reduced optic disk area with isolated tortuosity of the retinal veins.

CONCLUSIONS

Evaluation of optic nerve morphology, by digital image analysis, demonstrated that differences in ocular fundus morphology were correlated with differences in etiology and timing of the adverse event occurring in prenatal and perinatal life. In addition, digital image analysis may be a helpful tool for understanding variations in optic nerve and retinal vessel morphology and their relationship with central nervous pathology.

Retinopathy of prematurity in infants < 32 weeks' gestation at birth in New South Wales in 1993 and 1994

OBJECTIVE

To study the incidence and severity of retinopathy of prematurity (ROP) in infants < 32 weeks' gestation.

DESIGN

Review of the records maintained in the New South Wales Neonatal Intensive Care Unit Study (NICUS) database on infants admitted to the neonatal intensive care units (NICU) in NSW from 1 January 1993 to 31 December 1994.

RESULTS

In the more premature infants, 23-26 weeks' gestation, 65% developed ROP (102 of 157 examined for ROP). Forty-four infants (28%) developed severe ROP (Stage ≥ 3 ROP), 19 infants (12.1%) required cryo/laser therapy and one infant (0.6%) in this group had a retinal detachment. One hundred and fifty-seven of 159 surviving infants (98.7%) were examined for ROP. In the infants 27-28 weeks' gestation, 38.3% developed ROP (103 of 269 examined for ROP). Fifteen infants (5.6%) developed severe ROP, seven infants (2.6%) required cryo/laser therapy for threshold ROP and three infants (1.1%) in this group had a retinal detachment. Two hundred and sixty-nine of 299 surviving infants (90%) were examined for ROP. In the infants 29-31 weeks' gestation, 10.8% developed ROP (48 of 443 examined for ROP). Six infants (1.4%) developed severe ROP, one infant (0.2%) required cryo/laser therapy for threshold ROP and no infant in this group had a retinal detachment. However, only 443 of 681 surviving infants (65.1%) in this group were examined for ROP. Of the four infants with detached retinas, one was a 25 week gestation infant weighing 840 g, two were 27 weeks' gestation weighing 960 and 980 g and one infant was a 28 week gestation infant weighing 620 g. No infant developed Stage 5 ROP.

CONCLUSION

In the more mature infants 29-31 weeks' gestation, the rate of ROP is low, although severe ROP still occurs. However, only 65.1% of these infants were examined for ROP and we should be diligent in screening for ROP in the sicker infants in this group. The incidence of severe ROP as well as the rate of cryo/laser therapy in premature infants 23-26 weeks' in NSW has not changed since the increases seen in the early 1990s. Retinal detachment also occurs in the infants 27-28 weeks' gestation and it is important that all these infants are screened for ROP.

Risk factors for strabismus in children born before 32 weeks' gestation

AIM

To investigate risk factors associated with strabismus in children born prematurely.

METHODS

Prospective study of all children born before 32 weeks' gestation between 1 January 1990 and 31 December 1991 in a geographically defined population of approximately 3 million in the Northern Region of the United Kingdom. All children were examined aged 2 years by the same ophthalmologist and paediatrician.

RESULTS

558 children (98.6% of study group) were examined. Logistic regression showed an increased risk of strabismus in children with cicatricial retinopathy of prematurity (p=0.02), refractive error (p=0.003), family history of strabismus (p<0.0001), and poor neurodevelopmental outcome (p<0.0001), in particular impaired locomotor skills (p=0.008) and hand-eye coordination (p=0. 001). Gestational age and regressed acute ROP were not independent risk factors for strabismus (p=0.92 and 0.85 respectively).

CONCLUSIONS

This study has identified factors which are independently related to strabismus (although not necessarily causative) and others which are related only indirectly. This may contribute both to the management of children born prematurely and to future studies of the aetiology of strabismus.

Ophthalmological follow up of preterm infants: a population based, prospective study of visual acuity and strabismus

BACKGROUND/AIMS

Prematurely born infants are known to have an increased rate of ophthalmological morbidity. The aim of the present study was to investigate visual acuity and ocular alignment in a population of preterm infants in a geographical area, in infants with and without retinopathy of prematurity (ROP).

METHODS

A prospective population based study of ophthalmological status of preterm infants with a birth weight of 1500 g or less was performed during 3.5 years, with examinations at 6, 18, 30, and 42 months of corrected age. Visual acuity was tested using linear optotypes. Multiple regression analyses were used to analyse independent risk factors for poor vision and strabismus.

RESULTS

Poor vision (< 0.3) was detected in 2.5% (6/237) of the children. Of these, only two (0.8%) had a severe visual impairment (< 0.1). Strabismus occurred in 13.5% (31/229). Children with cryotreated ROP and neurological complications ran the highest risk of poor vision and strabismus, according to multiple regression analysis. Among children without a history of ROP or neurological complications, 34% had a visual acuity < 0.7 and 5.9% had strabismus, compared with 61% and 22%, respectively, among the children with ROP or neurological complications.

CONCLUSIONS

The overall incidence of subnormal vision and strabismus in children born prematurely was higher than in a full term population of the same age. On the basis of this study, follow up of all preterm infants screened for ROP is recommended and general guidelines are suggested.