Oculomotor consequences of intraventricular hemorrhages in premature infants

Prevalence and Types of Strabismus in Cerebral Palsy: A Global and Historical Perspective Based on a Systematic Review and Meta-Analysis

PURPOSE

Strabismus is more frequent in cerebral palsy (CP) than in the normal population, but reports differ how much it is increased. We here examined the global prevalence and types of strabismus in CP, whether esotropia or exotropia is more frequent, and whether the prevalence differs between ethnicities and/or country income levels, and between generations.

METHODS

We compiled in a systematic review and meta-analysis the results of 147 CP studies that report the prevalence of strabismus or the ratio of esotropia to exotropia, and we conducted subgroup analyses for region (income level) and ethnicity. We performed a pooled analysis for the CP strabismus prevalence, and estimated the global number of CP cases with strabismus.

RESULTS

The pooled prevalence of strabismus in CP is 49.8% in high-income countries and 39.8% in lower-income countries. We estimate the global number of strabismus cases in CP as 12.2 million, with 7.6 million males and 4.6 million females, based on current estimates of 29.6 million global CP cases. Esotropia is more frequent than exotropia in Caucasians, while exotropia is more frequent than esotropia in Hispanic and in some Asian and African populations. The strabismus prevalence in CP increases with increasing country income levels.

CONCLUSION

Generational changes in strabismus prevalence appear to reflect a transition of CP types and an increase in prevalence as countries attain higher income and more effective maternal health care. The distribution of esotropia and exotropia in CP patients largely reflects the horizontal strabismus type that is predominant in the subject's ethnicity.

Prevalence and types of strabismus in cerebral palsy: A global and historical perspective based on a systematic review and meta-analysis

Purpose

Strabismus is more frequent in cerebral palsy (CP) than in the normal population, but reports differ how much it is increased. We here examined the global prevalence and types of strabismus in CP, whether esotropia or exotropia is more frequent, and whether the prevalence differs between ethnicities and/or country income levels, and between generations.

Methods

We compiled in a systematic review and meta-analysis the results of 147 CP studies that report the prevalence of strabismus or the ratio of esotropia to exotropia, and we conducted subgroup analyses for region (income level) and ethnicity. We performed a pooled analysis for the CP strabismus prevalence, and estimated the global number of CP cases with strabismus.

Results

The pooled prevalence of strabismus in CP is 49.8% in high-income countries and 39.8% in lower-income countries. We estimate the global number of strabismus cases in CP as 12.2 million, with 7.6 million males and 4.6 million females, based on current estimates of 29.6 million global CP cases. Esotropia is more frequent than exotropia in Caucasians, while exotropia is more frequent than esotropia in Hispanic and in some Asian and African populations. The strabismus prevalence in CP increases with increasing country income levels.

Conclusion

Generational changes in strabismus prevalence appear to reflect a transition of CP types and an increase in prevalence as countries attain higher income and more effective maternal health care. The distribution of esotropia and exotropia in CP patients largely reflects the horizontal strabismus type that is predominant in the subject's ethnicity.

Strabismus at Age 2 Years in Children Born Before 28 Weeks' Gestation: Antecedents and Correlates

Children born very preterm are at greater risk of ophthalmic morbidities, including strabismus, than children born at term. We evaluated perinatal factors associated with strabismus at age 2 years in a large population of infants delivered before 28 weeks' gestation. A total of 996 infants in the multicenter ELGAN (Extremely Low Gestational Age Newborn) study who had a retinal exam in infancy and a developmental assessment at 2 years corrected age are included. Their mothers were interviewed about the pregnancy, and both mother and newborn charts were reviewed. Certified examiners administered the Bayley Scales of Infant Development-II and performed an examination of ocular alignment. Time-oriented logistic regression risk models were created to evaluate the associations of characteristics and exposures with the development of strabismus. Overall, 14% (n = 141) of the children had strabismus at 2 years, and 80% of strabismic children had esotropia. Characteristics associated with strabismus were birth before 26 weeks' gestation, severe fetal growth restriction, and maternal history of aspirin ingestion. Associated postnatal factors included a SNAP-II (Score for Neonatal Acute Physiology) illness severity value ≥ 30, brain ventriculomegaly, type I retinopathy of prematurity, and ventilator-dependent severe bronchopulmonary dysplasia. Strabismus in very preterm populations is associated with a number of antenatal and postnatal antecedents as well as clinical and imaging correlates indicative of brain damage in these children. Routine ophthalmologic assessments in the early years can allow appropriate and timely interventions.

Comitant strabismus: Perspectives, present and future

Comitant strabismus is a common condition affecting infants, children and adults. Its impact on the affected patient may be severe resulting in visual loss, lack of binocularity, diplopia, social stigma and multiple corrective surgeries within the affected individual's lifespan. It is therefore important that this prevalent disorder should be better understood. We review the current understanding of the demographics and what is known of the etiology, risk factors and genetics of strabismus. We stress the importance of careful clinical assessment in classifying strabismus, and the common pitfalls in the measurement and pre-operative sensory work-up of the strabismic patient. The fact strabismus is comitant does not indicate it is benign: acute onset of comitant esotropia may be a presenting sign of pontine or cerebellar tumor. Lastly, we review the impact of genetics on our understanding of strabismus. While the causes of many types of congenital incomitant strabismus have been elucidated through careful observation and genetic screening, the genetics of comitant strabismus are more complex and multifactorial. Only through careful study and recruitment of large groups of affected individuals and families can we start to answer the question: why is this group of patients pre-disposed to develop strabismus. Doing so will help identify patients at risk, to spare them from the significant morbidity associated with this common disorder.

Decorrelation of cerebral visual inputs as the sufficient cause of infantile esotropia

BACKGROUND AND PURPOSE

Human infants at greatest risk for esotropia are those who suffer cerebral insults that could decorrelate signals from the two eyes during an early critical period of binocular, visuomotor development. The authors reared normal infant monkeys under conditions of binocular decorrelation to determine if this alone was sufficient to cause esotropia, and associated behavioral as well as neuroanatomic deficits.

METHODS

Binocular decorrelation was imposed using prism-goggles for durations of 3-24 weeks (control monkeys wore plano goggles), emulating unrepaired strabismus of durations 3 months to 2 years in human infants. Behavioral recordings were obtained, followed by neuroanatomic analysis of ocular dominance columns and binocular, horizontal connections in the striate visual cortex (area V1).

RESULTS

Concomitant, constant esotropia developed in each monkey exposed to decorrelation for a duration of 6-24 weeks. The severity of ocular motor signs (esotropia angle; dissociated vertical deviation; latent nystagmus; pursuit / optokinetic tracking asymmetry; fusional vergence deficits), and the loss of V1 binocular connections increased as a function of decorrelation duration. Stereopsis was deficient and motion visually evoked potentials were asymmetric. Monkeys exposed to decorrelation for 3 weeks showed transient esotropia, but regained normal alignment, visuomotor behaviors, and binocular V1 connections.

CONCLUSIONS

Binocular decorrelation is a sufficient cause of infantile esotropia when imposed during a critical period of visuomotor development. The systematic relationship between severity of visuomotor signs and severity of V1 connectivity deficits provides a neuroanatomic mechanism for these signs. Restoration of binocular fusion and V1 connections after short durations of decorrelation helps explain the benefits of early strabismus repair in humans.

Estrabismo y ambliopía, conceptos básicos para el médico de atención primaria

El estrabismo y la ambliopía son patologías relativamente frecuentes en la población general. La ambliopía constituye la causa principal de disminución de visión unilateral. Existen diferentes tipos de estrabismo mientras que la ambliopía se debe únicamente a tres mecanismos fisiopatológicos. El objetivo de este artículo es brindar al médico de atención primaria y al estudiante de medicina una revisión completa y actualizada sobre estos dos temas. Para esto revisamos libros de texto reconocidos y utilizando MEDLINE, artículos representativos relacionados con el tema y mostramos un panorama general que incluye aspectos básicos de anatomía de los músculos extraoculares, nomenclatura y terminología empleada en estrabismo, aspectos de fisiología motora, pruebas clínicas utilizadas para el diagnóstico, generalidades sobre los principales tipos de estrabismo y manejo.

Strabismus, Binocular Functions and Ocular Motility in Children with Hydrocephalus

PURPOSE

To investigate heterotropia, heterophoria, head posture, nystagmus, stereo acuity, ocular motility and near point of convergence (NPC) in children with hydrocephalus treated surgically before 1 year of age. In addition, the effects of being born with hydrocephalus, the effect of the etiology of hydrocephalus, number of shunt revisions and the size of the ventricles on these variables were studied.

METHODS

A population-based study was performed in 75 children and the results were compared with the results of an age- and sex-matched group (comp group) (n = 140).

RESULTS

Heterotropia 68.9% (comp group 3.6%; p < 0.001), abnormal head posture 41.3% (comp group 0; p < 0.001), nystagmus 44.0% (comp group 0; p < 0.001), stereo acuity < or =60'' 33.8% (comp group 97.1%; p < 0.001) and ocular motility defects 69.7% (comp group 0.7%; p < 0.001) were more common among children with hydrocephalus than in the comparison group. Children with overt hydrocephalus at birth had significantly more heterotropia (p = 0.0006), esotropia (p = 0.002), abnormal head posture (p = 0.02) and motility defects (p = 0.003) compared to those with hydrocephalus developing during the first year of life. The etiology, number of shunt revisions and the size of the ventricles had no significant effect on any of the investigated variables.

CONCLUSIONS

Children with hydrocephalus surgically treated before the age of one year commonly present orthoptic abnormalities. The etiology of hydrocephalus, number of shunt revisions and ventricle size seem to be of minor importance compared with the age of onset of hydrocephalus with regard to the risk for orthoptic abnormalities.

[Cerebral visual impairment in brain-damaged children - four case studies]

Cerebral visual impairment is one of the main causes of childhood visual impairment in developed countries. These disorders are often linked with pre- or perinatal hypoxic brain injuries. The patterns of brain injuries depend on the severity and duration of hypoxia and the child's age. In premature children, periventricular leukomalacia affects the optic radiations and the subcortical visual brain. In full-term newborn babies, chronic hypoxia leads to the damage of the visual cortex and acute hypoxia damages the basal ganglia. They recover from cortical blindness in variable ways. Visual dysfunction is characterized by fixation troubles, subnormal acuity (crowding), difficulty with perceiving visual fields, movements, depth, cognitive defects (agnosia of images, objects or faces, visuospatial disorders), ocular motility disorders (tonic gaze deviation, strabismus, nystagmus). Accompanying these cerebral injuries, there are accommodation defects and optic disk abnormalities that vary according to the gestational age at the time of hypoxia.

Treated threshold stage 3 versus spontaneously regressed subthreshold stage 3 retinopathy of prematurity: a study of motility, refractive, and anatomical outcomes at 6 months and 36 months

AIM

To compare the visual acuity (VA), spherical equivalent refractive error, motility, and anatomical outcomes in children with treated regressed threshold stage 3 retinopathy of prematurity (ROP) and those with spontaneously regressed subthreshold stage 3 ROP.

METHOD

6 month and 3 year data collected from infants examined between 1989 and 1999 with regressed stage 3 ROP, with or without treatment were retrospectively reviewed.

RESULTS

85 infants were included in this study. 40 eyes received cryotherapy, 81 eyes laser photocoagulation, and 34 eyes had spontaneously regressed subthreshold stage 3 ROP. Grating acuity score > or =2 cycles/degree (c/d) at 6 months was predictive of optotype acuity > or =6/9 in 69% of eyes and a score <2 c/d at 6 months was predictive of acuity < 6/9 in 88% of eyes. Eyes with subthreshold stage 3 ROP were twice as likely to have VA of 6/9 or better at 36 months than the treated eyes. The mean spherical equivalent refractive error at 36 months was -6.5 dioptres (D) (-21.5D to +1.38D) in cryotherapy treated eyes, -2.4D (-13D to +4D) in the laser group, and -0.22D (-9D to +2.25D) in the subthreshold group. Eyes within the treated groups were more myopic than the eyes within the spontaneously regressed group (p = 0.005). At 36 months, 42 out of the 85 infants (that is, 49%) had strabismus (44% in the cryotherapy group, 26% in the laser group, and 25% in the subthreshold group). There was a statistically significant association between the presence of strabismus and anisometropia (p = 0.016) and strabismus and intraventricular haemorrhage (IVH) (p = 0.005). There was a statistically significant difference in the incidence of strabismus between mild and moderate and severe grade IVH (p = 0.01). Eight out of 40 eyes in the cryotherapy group and six out of the 81 eyes in the laser group developed macular ectopia. None of the eyes in the spontaneously regressed group had macular dragging.

CONCLUSIONS

In this study, the grating acuity at 6 months was a good predictor of the 3 year optotype acuity in all groups. Eyes with spontaneously regressed subthreshold stage 3 ROP were associated with better vision at 3 years of age and a lesser degree of myopia compared to the treated groups. Strabismus developed predominantly in the treated groups and was frequently associated with neurological damage and/or anisometropia. The spontaneously regressed subthreshold stage 3 group had a better anatomical outcome compared to the groups in which the retinopathy regressed following treatment.

Perinatal cortical and subcortical visual loss: mechanisms of injury and associated ophthalmologic signs

PURPOSE

To determine whether term and preterm injuries to the retrogeniculate visual system are associated with recognizable patterns of ophthalmologic abnormalities and whether these patterns can be attributed to cortical (gray matter) or subcortical (white matter) injury.

DESIGN

A retrospective case series.

PARTICIPANTS

One hundred children with clinical and neuroimaging signs of perinatal posterior visual pathway injury who were examined at Arkansas Children's Hospital Eye Clinic between 1989 and 1999.

METHODS

We reviewed magnetic resonance images or computed tomographic scans from 50 children with cortical (predominantly or exclusively involving cortical gray matter) and 50 children with subcortical (predominantly or exclusively involving subcortical white matter) perinatal injury to the retrogeniculate visual system. Ophthalmologic abnormalities were analyzed retrospectively in each group.

MAIN OUTCOME MEASURES

Conjugate gaze deviation, type of strabismus, abnormal eye movements, and optic disc morphology.

RESULTS

Horizontal conjugate gaze deviation, exotropia, and a normal optic disc appearance were significantly more common in cortical than in subcortical visual loss. Tonic downgaze, esotropia, and optic nerve hypoplasia (with or without coexisting pallor) were significantly more common in subcortical than in cortical visual loss.

CONCLUSIONS

Perinatal cortical and subcortical visual loss produce differing profiles of ophthalmologic dysfunction. A reclassification of periventricular leukomalacia and other forms of retrogeniculate white matter injury as subcortical visual loss would increase diagnostic specificity.

Ocular significance of intraventricular haemorrhage in premature infants

AIM

To document ocular outcome in premature infants with intraventricular haemorrhages (IVH).

METHODS

68 preterm infants with IVH were examined.

RESULTS

Mean gestational age was 28.1 weeks (range 24-35). Mean birth weight was 1045.9 g (630-2240). Mean follow up was 54.6 months (6-150). IVH is graded from 1 to 4 based on the severity of haemorrhages. The incidence of ocular abnormalities was compared between low grade IVH (grade 1 and 2) and high grade IVH (grade 3 and 4). Of the 68 infants with IVH, ROP occurred in 33 infants (48.5%); 13 (43.3%) had low grade IVH; 20 (52.6%) had high grade IVH. Strabismus developed in 30 infants (44.1%); 14 (46.6%) had low grade IVH; 16 (42.1%) had high grade IVH. Infants with high grade IVH were at significant greater risk than infants with low grade IVH for the development of optic atrophy (31.5% v 16.6%), hydrocephalus (57.8% v 10%).

CONCLUSION

This study highlights the serious significance of all grades of IVH with the higher incidence of optic atrophy and hydrocephalus with high grade IVH.

The incidence of ophthalmologic interventions in children with birth weights less than 1251 grams. Results through 5 1/2 years. Cryotherapy for Retinopathy of Prematurity Cooperative Group

OBJECTIVE

This study aimed to report the frequency of ophthalmologic surgical and medical therapies provided to children with birth weights less than 1251 g who had all stages of retinopathy of prematurity (ROP). In addition, this study aimed to report the initial age at which such procedures are provided and to report the frequency of cerebrospinal fluid shunts.

DESIGN

Observational case series with prospective data collection.

PARTICIPANTS

Children from the Multicenter Trial of Cryotherapy for Retinopathy of Prematurity (CRYO-ROP) with birth weights less than 1251 g served as subjects. Group A included 257 children from all 23 CRYO-ROP study centers who had threshold ROP, who had participated in the randomized trial of cryotherapy, and who had survived to age 1 year. Group B included 1208 children from 5 of the 23 study centers who had varying severity of ROP (69 had threshold ROP) and who had participated in a 5 1/2-year study of the natural history of ROP.

MAIN OUTCOME MEASURES

Investigators documented medical and surgical ophthalmologic interventions through age 5 1/2 years as well as cerebrospinal fluid shunting surgery for hydrocephalus through age 2 years.

RESULTS

Group A was composed of 257 children with threshold ROP who underwent 226 ocular interventions in addition to cryotherapy (0.9 intervention per child). The most common treatments performed on the randomized cohort of children were vitrectomy (26% of patients), lensectomy (18%), amblyopia therapy (20%), and strabismus surgery (10%). Cataract surgery not associated with vitrectomy was performed infrequently (2%) and was performed equally often in treated and control eyes. Amblyopia therapy was prescribed as often for treated as for control eyes. Cerebrospinal fluid shunts were placed in 11% of these children. Group B was composed of 1208 natural history patients who underwent 239 ophthalmologic interventions (0.4 intervention per child). Strabismus surgery was the most commonly performed procedure for the natural history cohort of children (6% of the children). Amblyopia therapy was prescribed for 7% of the natural history patients. Cerebrospinal fluid shunts were required by 3% of the natural history infants, more often in children with more severe ROP.

CONCLUSIONS

These premature infants underwent a large number of ophthalmologic treatments during the first 5 1/2 years of life. The long-term costs of both extreme prematurity and ROP include not only the initial ablative therapy for ROP and societal loss due to blindness that still occurs in some cases, but also the ongoing costs of caring for eye problems.

Ocular morbidity in very low birth-weight infants with intraventricular hemorrhage

PURPOSE

To document ocular outcomes and prevalence of ocular disease in very low birth-weight infants with intraventricular hemorrhage.

METHODS

We retrospectively reviewed the records of all surviving very low birth-weight infants (1,500 g or less) admitted to the neonatal intensive care unit of our institution during 1992 and 1993. Of 252 survivors, 74 had complete ophthalmologic examinations at a mean adjusted age of 11 months. Of these 74 infants, 38 had intraventricular hemorrhage. Chi-square and multivariate analysis were used for statistical testing, in controlling for race, sex, and birth weight, and for other disease processes associated with prematurity.

RESULTS

Of 38 infants with intraventricular hemorrhage, strabismus occurred in 14 (37%), esotropia in 12 (32%), and exotropia in two (5%). Of the 20 infants with grades III and IV intraventricular hemorrhage, 11 (55%) had esotropia; none had exotropia. Infants with grades III and IV intraventricular hemorrhage were at significantly greater risk for the development of esotropia than were infants with less severe or no hemorrhage (odds ratio, 5.0; P = .04). Mean adjusted age at diagnosis of strabismus was 8.5 months. Infants with periventricular leukomalacia (odds ratio, 6.3; P = .036) and neonatal seizures (odds ratio, 7.3; P = .019) were at significantly greater risk of developing optic atrophy.

CONCLUSIONS

Very low birth-weight infants with more severe neurologic morbidity are at significant risk for development of esotropia and optic atrophy. Ophthalmologic screening of all very low birth-weight survivors may allow earlier diagnosis and intervention for these at-risk infants.

Are the pupils of premature infants affected by intraventricular hemorrhage?

The size and reactivity to light of the pupil in infants with intraventricular hemorrhage has been variously described in the literature. These descriptions have included miosis, reactivity to light, nonreactivity to light, and anisocoria. We studied the size and light reactivity of 20 infants with intraventricular hemorrhage compared with 30 controls. Both groups displayed a mean pupil diameter in relative darkness of 3.0 to 4.0 mm at various postconceptional ages (P > .05). The age of first response to light was about 30 weeks after conception in each group (P > .05). The severity of intraventricular hemorrhage as determined by ultrasound was not related to the pupil diameter in relative darkness. In general, the pupils of neonates are not affected by intraventricular hemorrhage.

Perinatal predictors of ocular morbidity in school children who were very low birthweight

Two hundred children from one neonatal intensive care unit (NICU), who were very low birthweight (VLBW), were examined at approximately 9 years of age and compared with a control group of normal birthweight children. Visual morbidity was significantly higher among children who were very low birthweight. Binocular visual acuity of 6/9 or worse was noted in 21 (10.5%), strabismus in 38 (19%) and regressed retinopathy of prematurity (ROP) in 13 (6.7%) of these children. A history of seizures in the perinatal period was highly correlated with poor visual acuity. Independently significant factors associated with strabismus included clinically diagnosed intraventricular haemorrhage, a maternal history of neonatal death, transfer from another hospital, bronchopulmonary dysplasia and necrotising enterocolitis. Perinatal variables that correlated with regressed ROP included birthweight, time from birth to admission to the NICU, necrotising enterocolitis and a history of maternal smoking during the pregnancy. When screening for ocular abnormalities among children who were born preterm, particular attention should be given to children with these risk factors.

Photorefraction screening in premature infants

BACKGROUND

Photorefraction is a screening technique capable of detecting potentially amblyogenic ophthalmic abnormalities. This screening technique was included as part of a longitudinal outpatient follow-up program of premature infants. The purpose of this investigation is to test the applicability of this screening method in a population of infants at risk for visual compromise.

METHODS

One-hundred eighty-two premature infants older than 3 months chronologic age were screened using a commercially available, off-axis photorefraction device. Ophthalmic examinations were performed concomitant with each photorefraction. In most cases, photorefractions were performed before and after administration of cycloplegic medications. All photorefractions were analyzed by an observer masked to the results of the ophthalmic examination.

RESULTS

For the 182 patients, the mean birth weight and mean gestational age were 1034.5 g and 28.2 weeks, respectively. The prevalence of ophthalmic abnormalities in the study population was 18%. Sensitivity and specificity rates for the overall screening were 77% and 90%, respectively. Photorefractions were analyzable in 77% of patients studied, with the remaining 23% of our study population unsuccessfully screened. Very young infants (younger than 3 months corrected age) were particularly difficult to photograph, as evidenced by the preponderance of these patients (85%) in the nonanalyzable group. The readability of photorefractions in black infants was improved when cycloplegia was used for the photorefraction.

CONCLUSION

Photorefraction screening was an acceptable method of screening for ophthalmic abnormalities in a group of premature infants. Future studies of photorefraction screening techniques in premature infants will need to improve the success rate in young infants, perhaps by improving the fixation device.

Ocular findings in premature infants with grade IV intraventricular hemorrhage

Grade IV intraventricular hemorrhage (IVH) is a severe complication of premature birth. We retrospectively performed serial exams on 13 infants with grade IV IVH and compared their ocular findings to 11 infants matched by gestational age and birth weight without an IVH. All children in the study were initially examined in the neonatal unit within 8 weeks after birth. Subsequent periodic eye exams were performed until 3 to 7 years of age. Of the 13 grade IV IVHs, there was a 92% incidence of ocular abnormalities, compared to a 73% incidence in the premature group without IVH. The children with grade IV hemorrhages had a statistically significant increased incidence of severe eye disease with resultant visual loss (38%) compared to the non-IVH group. Loss of vision was due to optic atrophy and retinopathy of prematurity. Grade IV IVH children are at high risk for severe eye disease and should have early and frequent ophthalmologic exams.

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

We studied the prevalence of ocular abnormalities in 528 children born prematurely (less than 1,501-g birth weight, less than 33 weeks' gestational age, or both) in Stockholm County from 1976 to 1981. The control group consisted of 1,047 randomly selected full-term children. Through various searches of the ophthalmic records from the period of 1981 to 1986 of Stockholm County, we found that 134 of the 528 premature children (25.4%) and 121 of the 1,047 full-term children (11.5%) had needed ophthalmic care for different reasons. The prevalence of ocular abnormalities was much higher in premature children than in full-term children: reduced visual acuity of 20/33 or worse in the best eye (21 of 528 [4.0%] and one of 1,047 [0.1%]); myopia (33 of 528 [6.3%] and 18 of 1,047 [1.8%]); anisometropia of 1 diopter or greater (31 of 528 [5.9%] and 15 of 1,047 [1.5%]); strabismus (52 of 528 [9.9%] and 22 of 1,047 [2.1%]); and nystagmus (13 of 528 [2.4%] and one of 1,047 [0.1%]). Children with birth weight less than 1,000 g had the highest rates of ocular abnormalities. We conclude that visual and oculomotor development of premature children should be carefully examined.

Optic nerve hypoplasia, encephalopathy, and neurodevelopmental handicap

Abnormalities of the central nervous system are frequently described in optic nerve hypoplasia. In a longitudinal study of 46 consecutive children (32 term, 14 preterm) with bilateral optic nerve hypoplasia 32 (69.5%) had associated neurodevelopmental handicap. Of these, 90% had structural central nervous system abnormalities on computed tomographic brain scans. Neurodevelopmental handicap occurred in 62.5% of the term and 86% of the preterm infants respectively. Term infants had a greater incidence of ventral developmental midline defects and proportionately fewer maternal and/or neonatal complications throughout pregnancy, while encephaloclastic lesions were commoner among the premature infants. An association of optic nerve hypoplasia with the twin transfusion syndrome and prenatal vascular encephalopathies is described.