Brain injury and the eye

Neurological and Visual Outcomes in Infants and Toddlers Following Therapeutic Hypothermia for Neonatal Hypoxic-Ischemic Encephalopathy

BACKGROUND

The majority of studies have investigated neurodevelopmental outcomes, whereas visual impairment is less explored in children with a history of neonatal (hypoxic-ischemic) encephalopathy. Our aim was to perform a detailed neurological and visual assessment and also to investigate the presence of cerebral visual impairment in infants and toddlers with neonatal encephalopathy.

METHODS

Thirty participants with a history of neonatal encephalopathy, who had been hospitalized for therapeutic hypothermia, underwent a detailed neurological examination at age five to 36 months. Age-matched, 30 healthy children were also enrolled as a control group. All children in the study and control groups received neurological and a comprehensive ophthalmologic examination, including visual field and visual acuity. Presence of cerebral visual impairment was also evaluated clinically.

RESULTS

Rates of cerebral palsy, severe motor impairment, cognitive impairment, epilepsy, and cerebral visual impairment were found to be 20%, 10%, 15.3%, 10%, and 20%, respectively. When compared with healthy controls, oculomotor functions, pupillary light response, refractive parameters, anterior/posterior segment examinations, ocular visual impairment rates, and last, visual acuities were found similar. However, we found a statistically significant increase in visual field defects in our study group.

CONCLUSIONS

It could be better to perform a comprehensive ophthalmologic examination including visual field, visual acuity, and oculomotor functions by a pediatric ophthalmologist to accurately diagnose neurovisual deficits in infants following therapeutic hypothermia. Early identification and rehabilitation of the visual deficits might improve the neurodevelopment in these children.

Ocular neovascularization following hypoxic ischemic encephalopathy

We present the findings of 2 children with neonatal hypoxic ischemic encephalopathy (HIE), who demonstrated ocular neovascularization at birth. While the cerebral effects of HIE have been well described, ocular effects have not. Our cases, combined with recent published laboratory research, demonstrate that significant ocular effects may accompany HIE.

Abnormal Vestibular-Ocular Reflexes in Children With Cortical Visual Impairment

BACKGROUND

To determine whether the vestibular-ocular reflexes (VORs) can be affected by central nervous system injury in children with cortical visual impairment (CVI).

METHODS

Retrospective case series. Twenty consecutive children with CVI who presented to a pediatric ophthalmology practice over an 18-month period were included in the study. Horizontal and vertical VORs were assessed by a pediatric neuro-ophthalmologist using the standard doll's head maneuver. MRI studies were independently reviewed by a pediatric neuroradiologist in a masked fashion. The main outcome measures were the integrity of the VORs and the presence of brainstem abnormalities on MRI.

RESULTS

VORs were found to be absent or severely impaired in 13/20 (65%) children with CVI. More surprisingly, the doll's head maneuver failed to substantially overcome the deviated eye position in 8/13 (62%) children with conjugate gaze deviations. Reduced brainstem size and signal abnormalities were found in 4/7 children with normal VORs and in 9/13 children with abnormal VORs (P = 0.6), showing noncorrelation with the integrity of the VOR.

CONCLUSION

VORs are commonly impaired in children with CVI. This ocular motor deficit reflects the diffuse cortical and subcortical injury that often accompanies perinatal injury to the developing brain. Consequently, these children may lack important visual compensatory mechanisms to stabilize gaze during head movements. This knowledge can help in planning visual rehabilitation.

Utilising the Orthoptic Skill Set to Improve Access to Eye Care for Adults with Severe/Profound Learning Disabilities-A Service Evaluation

Intro:

There is a wealth of research evidencing the high incidence of visual impairment (VI) and poor uptake of eye care services by adults with learning disabilities (LD). Despite this, very few authorities within England currently provide the additional support required by those with severe/profound LD (S/PLD).

Method:

By means of an initial funded pilot study, an unmet need was evidenced locally and a small service established to improve access to eye care for adults with S/PLD. Operational since 2007, this service has provided evidence to support the campaign for a nationally funded eye care pathway.

This service evaluation outlines the initial service set up, aims and objectives, and provides an analysis of the current service by means of a detailed breakdown of service-user outcomes during a sample 5-year period.

Results:

Orthoptic home visits (OHV) revealed high levels of strabismus (54.4%), refractive error (43.3%), cataracts (23.3%), and many other ophthalmic conditions (29%). Over a quarter of the adults with LD (26.6%) were certified as VI and 61% of people were provided with tailored strategies, the majority of which were for visual processing difficulties.

Conclusion:

The prospect of a nationally funded eye care pathway for adults with LD in England is now a real possibility. This service model has identified a clearly defined unmet need and illustrates the unique skill set orthoptists can offer to address this health inequality. Requiring minimal financial outlay and flexible enough to be integrated into any future national eye care framework, this service has ensured that access to eye care is truly equitable for all people with LD.

Spectral-domain OCT changes in retina and optic nerve in children with hypoxic-ischaemic encephalopathy

Purpose

To evaluate the effect of neonatal hypoxic–ischaemic injury on the retina and the optic nerve and to correlate ocular damage with systemic parameters, laboratory tests, neurological imaging and therapeutic hypothermia at birth.

Methods

Forty-one children with hypoxic–ischaemic encephalopathy (HIE) at birth (9.09 ± 3.78 years) and a control group of 38 healthy subjects (9.57 ± 3.47 years) were enrolled in a cohort study. The HIE population was divided into three subgroups, based on the degree of encephalopathy according to Sarnat score and the treatment with therapeutic hypothermia (TH): Sarnat score I not treated with hypothermia, Sarnat score II-III treated with TH and Sarnat score II-III not subjected to TH. Total macular thickness, individual retinal layers and peripapillary nerve fibre layer thickness were measured with spectral-domain optical coherence tomography. Clinical data of perinatal period of HIE children were collected: APGAR score, pH and base excess of funiculus blood at birth, apnoea duration, brain ultrasound, cerebral MRI ischaemic lesions and blood chemistry tests.

Results

Children with Sarnat score I did not show a reduction of peripapillary nerve fibres and ganglion cell layer compared to the control group (p = 0.387, p = 0.316). Peripapillary nerve fibre layer was 109.06 ± 7.79 μm in children with Sarnat score II-III treated with TH, 108.31 ± 7.83 μm in subjects with Sarnat score II-III not subjected to TH and 114.27 ± 6.81 μm in the control group (p = 0.028, p = 0.007). Ganglion cell layer was thinner in children with Sarnat score II-III treated with TH (50.31 ± 5.13 μm) compared to the control group (54.04 ± 2.81 μm) (p = 0.01). Inner retinal layers damage correlated with C-reactive protein and lactate dehydrogenase increase, while higher levels of total bilirubin were protective against retinal impairment (p < 0.05). Cerebral oedema was related to peripapillary nerve fibre layer damage (p = 0.046).

Conclusions

Thickness reduction of inner retinal layer and peripapillary nerve fibre impairment was related to encephalopathy severity. Ocular damage was associated with inflammation and cerebral oedema following hypoxic–ischaemic damage.

Evidence-Based Clinical Practice Guideline: Comprehensive Pediatric Eye and Vision Examination

Republished with written permission granted from the American Optometric Association, October 2, 2020.

The value of the visual evoked potentials test in the assessment of the visual pathway in head trauma

Background:

The research was done to evaluate the value of the visual evoked potentials test in the assessment of visual pathways function in cases with head trauma and minimal findings on routine testing.

Methods:

A prospective case series evaluating use of visual evoked potentials testing in patients with a history of head trauma and suffering from visual symptoms with no significant clinical and neuroimaging findings, referred for further work up.

Results:

Thirty-four patients with a history of head trauma and subsequent visual complaints were included. 27 cases (79.4%) were male and 7 cases (20.6%) were female. The mean elapsed time after the trauma was 47.6 weeks (range: 3.5 to 320 weeks). Twenty-five cases had unilateral and 9 cases had bilateral visual complaints. History of coma with mean duration of 12 days was present in 4 cases. The best-corrected visual acuity was less than 1 Log MAR (legally blind) in 21 eyes. In 4 eyes (12%) the relative afferent papillary defect test was positive. Mild to moderate optic disc pallor was present bilaterally in 4 cases and unilaterally in 3 cases. Hemorrhagic patches were reported on MRI in 2 cases; no other cases had pathologic MRI findings. In unilateral cases, there was a statistically significant difference between the involved eye-sided lobe and the sound eye-sided lobe implicit time and amplitude. In patients with bilateral complaints, by testing each eye, the VEP amplitudes of both eyes showed significant differences with the International Society for Clinical Electrophysiology of Vision standards, whereas the implicit times showed not-statistically significant differences.

Conclusions:

The visual evoked potentials test shows not only additional diagnostic value, not seen on routine clinical and neuroimaging testing, but also rather a high validity in tracing visual disability in traumatic brain injury.

Prenatal or Perinatal Injury? Diagnosing the Cortically Blind Infant

PURPOSE

To document the association of prenatal brain disruption with secondary perinatal distress in children diagnosed as having cortical visual impairment (CVI).

DESIGN

Retrospective case series.

METHODS

Eight children with severe CVI and clinical history of perinatal events were included. Case histories and neuroimaging studies were reviewed. The main outcome measures were perinatal history, visual and neurologic findings, and magnetic resonance (MR) imaging.

RESULTS

In our patient cohort, MR imaging showed signs of cortical dysgenesis leading to congenital brain malformations such as polymicrogyria consistent with a prenatal timing of CNS injury. Although subcortical white matter changes were common, signs of watershed injury to the visual cortex were absent, suggesting that the visual loss was attributable to a prenatal etiology with secondary birth complications.

CONCLUSION

Some children with CVI and a history of perinatal distress have prenatal dysgenesis of the developing brain. Therefore, a clinical history of perinatal hypoxia-ischemia is nonspecific and merits neuroimaging to identify antecedent brain malformations and timing of injury, which can influence patient diagnosis and management.

Neuroplasticity in cerebral visual impairment (CVI): Assessing functional vision and the neurophysiological correlates of dorsal stream dysfunction

Cerebral visual impairment (CVI) results from perinatal injury to visual processing structures and pathways and is the most common individual cause of pediatric visual impairment and blindness in developed countries. While there is mounting evidence demonstrating extensive neuroplastic reorganization in early onset, profound ocular blindness, how the brain reorganizes in the setting of congenital damage to cerebral (i.e. retro-geniculate) visual pathways remains comparatively poorly understood. Individuals with CVI exhibit a wide range of visual deficits and, in particular, present with impairments of higher order visual spatial processing (referred to as "dorsal stream dysfunction") as well as object recognition (associated with processing along the ventral stream). In this review, we discuss the need for ongoing work to develop novel, neuroscience-inspired approaches to investigate functional visual deficits in this population. We also outline the role played by advanced structural and functional neuroimaging in helping to elucidate the underlying neurophysiology of CVI, and highlight key differences with regard to patterns of neural reorganization previously described in ocular blindness.

Impact of prematurity on neurodevelopment

The consequences of prematurity on brain functional development are numerous and diverse, and impact all brain functions at different levels. Prematurity occurs between 22 and 36 weeks of gestation. This period is marked by extreme dynamics in the physiologic maturation, structural, and functional processes. These different processes appear sequentially or simultaneously. They are dependent on genetic and/or environmental factors. Disturbance of these processes or of the fine-tuning between them, when caring for premature children, is likely to induce disturbances in the structural and functional development of the immature neural networks. These will appear as impairments in learning skills progress and are likely to have a lasting impact on the development of children born prematurely. The level of severity depends on the initial alteration, whether structural or functional. In this chapter, after having briefly reviewed the neurodevelopmental, structural, and functional processes, we describe, in a nonexhaustive manner, the impact of prematurity on the different brain, motor, sensory, and cognitive functions.

The Assessment of Visual Function and Functional Vision

The complete assessment of vision-related abilities should consider visual function (the performance of components of the visual system) and functional vision (visual task-related ability). Assessment methods are highly dependent upon individual characteristics (eg, the presence and type of visual impairment). Typical visual function tests assess factors such as visual acuity, contrast sensitivity, color, depth, and motion perception. These properties each represent an aspect of visual function and may impact an individual's level of functional vision. The goal of any functional vision assessment should be to measure the visual task-related ability under real-world scenarios. Recent technological advancements such as virtual reality can provide new opportunities to improve traditional vision assessments by providing novel objective and ecologically valid measurements of performance, and allowing for the investigation of their neural basis. In this review, visual function and functional vision evaluation approaches are discussed in the context of traditional and novel acquisition methods.

Ophthalmic outcomes following neonatal hypoxic ischaemic encephalopathy; oculomotor, biometric and refractive data in early childhood

OBJECTIVES

To investigate the functional and structural impact of neonatal hypoxic ischaemic encephalopathy (HIE) on childhood visual development.

METHODS

In a prospective study, the neurocognitive outcomes of 42 children with a history of neonatal HIE were assessed serially up to 5 years. For the ophthalmic component of the study, visual, refractive, orthoptic and ocular biometry measurements were obtained in 32 children, with axial length measurements estimated using the IOLMaster.

RESULTS

For the 32 children who completed the ophthalmic component of the study, severity of HIE grade was determined to be mild, moderate, or severe in 18 (56.3%), 13 (40.6%), and 1 (3.1%) cases, respectively. One (3.1%) child was classed as visually impaired. Twelve (37.5%) were found to have ametropia. Mean (±SD) axial length was 22.09 (±0.81) mm, within the normal range for the age of this cohort. Seven of the 42 (16.7%) children who were involved in the larger neurodevelopmental arm of the study had clinical evidence of a squint. There was no correlation between the severity of HIE grade at birth and axial length or occurrence of squint.

CONCLUSIONS

Neonatal HIE is associated with a higher incidence of squint compared with the general paediatric population. This occurred irrespective of severity of HIE grade. The ocular biometry measurements were consistent with published normative data, and no significant difference in ocular biometry was demonstrated between HIE severity groups.

Attenuation of Retinal Vascular Development in Neonatal Mice Subjected to Hypoxic-Ischemic Encephalopathy

A significant proportion of children that survive hypoxic-ischemic encephalopathy (HIE) develop visual impairment. These visual deficits are generally attributed to injuries that occur in the primary visual cortex and other visual processing systems. Recent studies suggested that neuronal damage might also occur in the retina. An important structure affecting the viability of retinal neurons is the vasculature. However, the effects of HIE on the retinal neurovasculature have not been systemically evaluated. Here we investigated whether exposure of postnatal day 9 (P9) neonatal mice to HIE is sufficient to induce neurovascular damage in the retina. We demonstrate that the blood vessels on the surface of the retina, from mice subjected to HIE, were abnormally enlarged with signs of degeneration. The intermediate and deep vascular layers in these retinas failed to form normally, particularly in the periphery. All the vascular damages observed here were irreversible in nature up to 100 days post HIE. We also observed loss of retinal neurons, together with changes in both astrocytes and Müller cells mainly in the inner retina at the periphery. Collectively, our findings suggest that HIE results in profound alterations in the retinal vasculature, indicating the importance of developing therapeutic strategies to protect neurovascular dysfunction not only in the brain but also in the retina for infants exposed to HIE.

ERGs on the brain: the benefits of simultaneous flash retinal and cortical responses in paediatric cerebral visual impairment

Purpose

To highlight the importance of simultaneous flash electroretinogram (ERG) and visual evoked potential (VEP) recording to differentiate a true flash VEP response from an artefact caused by the intrusion of the ERG on a mid-frontal reference electrode in cases of severe cerebral visual impairment (CVI).

Methods

We report an observational case series of four children with severe CVI who underwent simultaneous flash ERG and VEP recordings. Flash VEPs from Oz–Fz and lower lid skin ERGs referred to Fz were recorded simultaneously to Grass intensity setting 4 flash stimulation.

Results

In all cases, atypical, but reproducible VEPs were evident. Comparison of the timing and waveform of the VEPs and ERGs showed the occipital responses were inverted ERGs and no true flash VEP was evident.

Conclusions

While ISCEV and neurophysiology standards do not require the simultaneous recording of the flash ERG with the VEP, these cases highlight the usefulness of this non-invasive technique particularly in suspected paediatric cerebral visual impairment to differentiate a true VEP from an artefact caused by ERG contamination.

Cerebral malaria induces electrophysiological and neurochemical impairment in mice retinal tissue: possible effect on glutathione and glutamatergic system

Background

Cerebral malaria (CM) is a severe complication resulting from Plasmodium falciparum infection. This condition has usually been associated with cognitive, behavioural and motor dysfunctions, being the retinopathy the most serious consequence resulting from the disease. The pathophysiological mechanisms underlying this complication remain incompletely understood. Several experimental models of CM have already been developed in order to clarify those mechanisms related to this syndrome. In this context, the present work has been performed to investigate which possible electrophysiological and neurochemistry alterations could be involved in the CM pathology.

Methods

Experimental CM was induced in Plasmodium berghei-infected male and female C57Bl/6 mice. The survival and neurological symptoms of CM were registered. Brains and retina were assayed for TNF levels and NOS2 expression. Electroretinography measurements were recorded to assessed a- and b-wave amplitudes and neurochemicals changes were evaluated by determination of glutamate and glutathione levels by HPLC.

Results

Susceptible C57Bl/6 mice infected with ≈ 10⁶ parasitized red blood cells (P. berghei ANKA strain), showed a low parasitaemia, with evident clinical signs as: respiratory failure, ataxia, hemiplegia, and coma followed by animal death. In parallel to the clinical characterization of CM, the retinal electrophysiological analysis showed an intense decrease of a- and-b-wave amplitude associated to cone photoreceptor response only at the 7 days post-infection. Neurochemical results demonstrated that the disease led to a decrease in the glutathione levels with 2 days post inoculation. It was also demonstrated that the increase in the glutathione levels during the infection was followed by the increase in the ³H-glutamate uptake rate (4 and 7 days post-infection), suggesting that CM condition causes an up-regulation of the transporters systems. Furthermore, these findings also highlighted that the electrophysiological and neurochemical alterations occurs in a manner independent on the establishment of an inflammatory response, once tumour necrosis factor levels and inducible nitric oxide synthase expression were altered only in the cerebral tissue but not in the retina.

Conclusions

In summary, these findings indicate for the first time that CM induces neurochemical and electrophysiological impairment in the mice retinal tissue, in a TNF-independent manner.

Disentangling How the Brain is "Wired" in Cortical (Cerebral) Visual Impairment

Cortical (cerebral) visual impairment (CVI) results from perinatal injury to visual processing structures and pathways of the brain and is the most common cause of severe visual impairment or blindness in children in developed countries. Children with CVI display a wide range of visual deficits including decreased visual acuity, impaired visual field function, as well as impairments in higher-order visual processing and attention. Together, these visual impairments can dramatically influence a child's development and well-being. Given the complex neurologic underpinnings of this condition, CVI is often undiagnosed by eye care practitioners. Furthermore, the neurophysiological basis of CVI in relation to observed visual processing deficits remains poorly understood. Here, we present some of the challenges associated with the clinical assessment and management of individuals with CVI. We discuss how advances in brain imaging are likely to help uncover the underlying neurophysiology of this condition. In particular, we demonstrate how structural and functional neuroimaging approaches can help gain insight into abnormalities of white matter connectivity and cortical activation patterns, respectively. Establishing a connection between how changes within the brain relate to visual impairments in CVI will be important for developing effective rehabilitative and education strategies for individuals living with this condition.

Cerebral versus Ocular Visual Impairment: The Impact on Developmental Neuroplasticity

Cortical/cerebral visual impairment (CVI) is clinically defined as significant visual dysfunction caused by injury to visual pathways and structures occurring during early perinatal development. Depending on the location and extent of damage, children with CVI often present with a myriad of visual deficits including decreased visual acuity and impaired visual field function. Most striking, however, are impairments in visual processing and attention which have a significant impact on learning, development, and independence. Within the educational arena, current evidence suggests that strategies designed for individuals with ocular visual impairment are not effective in the case of CVI. We propose that this variance may be related to differences in compensatory neuroplasticity related to the type of visual impairment, as well as underlying alterations in brain structural connectivity. We discuss the etiology and nature of visual impairments related to CVI, and how advanced neuroimaging techniques (i.e., diffusion-based imaging) may help uncover differences between ocular and cerebral causes of visual dysfunction. Revealing these differences may help in developing future strategies for the education and rehabilitation of individuals living with visual impairment.

Transient cortical visual impairment after video-assisted thoracic surgery: a case report

Background

Visual loss associated with thoracic surgery has been reported mostly after coronary angiography or bypass surgery. The position of video-assisted thoracic surgery (VATS) is usually lateral, thus not compressive to the globe. Visual loss after VATS has not been reported. Herein we report a patient without any cardiovascular risk factors who experienced transient cortical blindness after an uneventful VATS.

Case presentation

A 40-year-old man noticed a visual loss at the recovery room after VATS. He showed normal pupillary reflex, normal optic disc appearance, and homonymous hemianopia respecting the vertical meridian, thus was typical for cortical visual impairment.

Conclusions

Transient cortical visual impairment could be encountered after an uneventful VATS in a patient without any cardiovascular risk factors.

Children and youth with 'unspecified injury to the head': implications for traumatic brain injury research and surveillance

Background

The case definition for traumatic brain injury (TBI) often includes ‘unspecified injury to the head’ diagnostic codes. However, research has shown that the inclusion of these codes leads to false positives. As such, it is important to determine the degree to which inclusion of these codes affect the overall numbers and profiles of the TBI population. The objective of this paper was to profile and compare the demographic and clinical characteristics, intention and mechanism of injury, and discharge disposition of hospitalized children and youth aged 19 years and under using (1) an inclusive TBI case definition that included ‘unspecified injury to the head’ diagnostic codes, (2) a restricted TBI case definition that excluded ‘unspecified injury to the head ‘diagnostic codes, and (3) the ‘unspecified injury to the head’ only case definition.

Methods

The National Ambulatory Care Reporting System and the Discharge Abstract Database from Ontario, Canada, were used to identify cases between fiscal years 2003/04 and 2009/10.

Results

The rate of TBI episodes of care using the inclusive case definition for TBI (2,667.2 per 100,000) was 1.65 times higher than that of the restricted case definition (1,613.3 per 100,000). ‘Unspecified injury to the head’ diagnostic codes made up of 39.5 % of all cases identified with the inclusive case definition. Exclusion of ‘unspecified injury to the head’ diagnostic code in the TBI case definition resulted in a significantly higher proportion of patients in the intensive care units (p < .0001; 18.5 % vs. 22.2 %) and discharged to a non-home setting (p < .0001; 9.9 % vs. 11.6 %).

Conclusion

Inclusion of ‘unspecified injury to the head’ diagnostic codes resulted in significant changes in numbers, healthcare use, and causes of TBI. Careful consideration of the inclusion of ‘unspecified injury to the head’ diagnostic codes in the case definition of TBI for the children and youth population is important, as it has implications for the numbers used for policy, resource allocation, prevention, and planning of healthcare services. This paper can inform future work on reaching consensus on the diagnostic codes for defining TBI in children and youth.

Defining pediatric traumatic brain injury using International Classification of Diseases Version 10 Codes: a systematic review

BACKGROUND

Although healthcare administrative data are commonly used for traumatic brain injury (TBI) research, there is currently no consensus or consistency on the International Classification of Diseases Version 10 (ICD-10) codes used to define TBI among children and youth internationally. This study systematically reviewed the literature to explore the range of ICD-10 codes that are used to define TBI in this population. The identification of the range of ICD-10 codes to define this population in administrative data is crucial, as it has implications for policy, resource allocation, planning of healthcare services, and prevention strategies.

METHODS

The databases MEDLINE, MEDLINE In-Process, Embase, PsychINFO, CINAHL, SPORTDiscus, and Cochrane Database of Systematic Reviews were systematically searched. Grey literature was searched using Grey Matters and Google. Reference lists of included articles were also searched for relevant studies. Two reviewers independently screened all titles and abstracts using pre-defined inclusion and exclusion criteria. A full text screen was conducted on articles that met the first screen inclusion criteria. All full text articles that met the pre-defined inclusion criteria were included for analysis in this systematic review.

RESULTS

A total of 1,326 publications were identified through the predetermined search strategy and 32 articles/reports met all eligibility criteria for inclusion in this review. Five articles specifically examined children and youth aged 19 years or under with TBI. ICD-10 case definitions ranged from the broad injuries to the head codes (ICD-10 S00 to S09) to concussion only (S06.0). There was overwhelming consensus on the inclusion of ICD-10 code S06, intracranial injury, while codes S00 (superficial injury of the head), S03 (dislocation, sprain, and strain of joints and ligaments of head), and S05 (injury of eye and orbit) were only used by articles that examined head injury, none of which specifically examined children and youth.

CONCLUSION

This review provides evidence for discussion on how best to use ICD codes for different goals. This is an important first step in reaching an appropriate definition and can inform future work on reaching consensus on the ICD-10 codes to define TBI for this vulnerable population.

Antecedents and correlates of visual field deficits in children born extremely preterm

AIM

We sought to identify the antecedents and correlates of visual field deficits (VFDs) at age 2 years among infants born before the 28th week of gestation.

METHODS

The visual fields of 1023 infants were assessed by confrontation at age 2 years. We compared the ante-and postnatal characteristics and exposures of the 65 infants with a VFD to their peers who did not have a VFD. We used time-oriented logistic regression risk models to assess the associations of potential antecedents and correlates with a VFD.

RESULTS

In the final regression model, VFD was associated with maternal consumption of aspirin during the current pregnancy, recurring/persistent acidemia during the first 3 postnatal days, cerebral ventriculomegaly seen on neonatal ultrasound, prethreshold retinopathy of prematurity (ROP), and supplemental oxygen and ventilator dependence at 36 weeks post-menstrual age. Birth before the 27th week was also associated with increased risk, but its significance was diminished by the addition of postnatal variables.

CONCLUSION

In this sample of extremely preterm born infants, antenatal as well as early and late postnatal characteristics and exposures are associated with an increased risk of having a VFD. Our study adds to our knowledge about the complex etiology of visual deficits of prematurity, and supports a multifactorial cause of these deficits.

Long-term effects of neonatal hypoxia-ischemia on structural and physiological integrity of the eye and visual pathway by multimodal MRI

PURPOSE

Neonatal hypoxia-ischemia is a major cause of brain damage in infants and may frequently present visual impairments. Although advancements in perinatal care have increased survival, the pathogenesis of hypoxic-ischemic injury and the long-term consequences to the visual system remain unclear. We hypothesized that neonatal hypoxia-ischemia can lead to chronic, MRI-detectable structural and physiological alterations in both the eye and the brain's visual pathways.

METHODS

Eight Sprague-Dawley rats underwent ligation of the left common carotid artery followed by hypoxia for 2 hours at postnatal day 7. One year later, T2-weighted MRI, gadolinium-enhanced MRI, chromium-enhanced MRI, manganese-enhanced MRI, and diffusion tensor MRI (DTI) of the visual system were evaluated and compared between opposite hemispheres using a 7-Tesla scanner.

RESULTS

Within the eyeball, systemic gadolinium administration revealed aqueous-vitreous or blood-ocular barrier leakage only in the ipsilesional left eye despite comparable aqueous humor dynamics in the anterior chamber of both eyes. Binocular intravitreal chromium injection showed compromised retinal integrity in the ipsilesional eye. Despite total loss of the ipsilesional visual cortex, both retinocollicular and retinogeniculate pathways projected from the contralesional eye toward ipsilesional visual cortex possessed stronger anterograde manganese transport and less disrupted structural integrity in DTI compared with the opposite hemispheres.

CONCLUSIONS

High-field, multimodal MRI demonstrated in vivo the long-term structural and physiological deficits in the eye and brain's visual pathways after unilateral neonatal hypoxic-ischemic injury. The remaining retinocollicular and retinogeniculate pathways appeared to be more vulnerable to anterograde degeneration from eye injury than retrograde, transsynaptic degeneration from visual cortex injury.

Repetitive mild traumatic brain injury causes optic nerve and retinal damage in a mouse model

There is increasing evidence that long-lasting morphologic and functional consequences can be present in the human visual system after repetitive mild traumatic brain injury (r-mTBI). The exact location and extent of the damage in this condition are not well understood. Using a recently developed mouse model of r-mTBI, we assessed the effects on the retina and optic nerve using histology and immunohistochemistry, electroretinography (ERG), and spectral-domain optical coherence tomography (SD-OCT) at 10 and 13 weeks after injury. Control mice received repetitive anesthesia alone (r-sham). We observed decreased optic nerve diameters and increased cellularity and areas of demyelination in optic nerves in r-mTBI versus r-sham mice. There were concomitant areas of decreased cellularity in the retinal ganglion cell layer and approximately 67% decrease in brain-specific homeobox/POU domain protein 3A-positive retinal ganglion cells in retinal flat mounts. Furthermore, SD-OCT demonstrated a detectable thinning of the inner retina; ERG demonstrated a decrease in the amplitude of the photopic negative response without any change in a- or b-wave amplitude or timing. Thus, the ERG and SD-OCT data correlated well with changes detected by morphometric, histologic, and immunohistochemical methods, thereby supporting the use of these noninvasive methods in the assessment of visual function and morphology in clinical cases of mTBI.

Visual function in preterm infants: visualizing the brain to improve prognosis

Considerable development of the visual system occurs in the third trimester of life, a time when very preterm-born infants are in a neonatal intensive care unit (NICU). Their very early birth during a period of rapid and marked neurodevelopment and their clinical course makes them a very high-risk population. A range of different events impacts brain development and the visual system, leading to significant long-term visual dysfunction. Improved neuroimaging techniques provide an important window on the early brain and visual system development of these vulnerable infants. Greater understanding of the etiology of visual impairment subsequent to preterm birth and the timing of critical processes will allow early recognition and the earlier implementations of interventions. In the longer term, this will help clinicians optimize NICU practice to reduce the incidence of visual dysfunction in these children.

Hypoxic-ischemic retinal injury in rat pups

BACKGROUND

Visual loss associated with brain damage, especially hypoxic-ischemic (HI) encephalopathy, is the most common cause of visual impairment in children in developed countries. We hypothesized that HI insults can cause long-term damage in immature eyes.

METHODS

In postnatal day 7 rat pups, HI was induced by unilateral common carotid artery ligation followed by hypoxia. Retina damage was assessed by electroretinography (ERG) and cell counting. Neuronal injury and astrogliosis were evaluated by terminal deoxynucleotidyl transferase nick-end labeling, cleaved caspase 3, ED1, and glial fibrillary acidic protein immunostaining.

RESULTS

We observed rapid and persistently extensive injuries in the ganglia cell layer (GCL), inner plexiform layer, and inner nuclear layer (INL) in ipsilateral retinas after HI injury, corresponding to the marked alteration in ERG. HI insult caused prominent microglial and Műller cell activation in ipsilateral inner retinas. Neuronal death in the GCL and INL after HI injury was mainly apoptotic, involving caspase-dependent pathways.

CONCLUSION

Our study demonstrated the first evidence of HI retinal damage at both the pathological and functional level using the Vannucci model in neonatal rats. Because retinal damage is often associated with HI injury, it is important to demonstrate that a particular neuroprotective strategy effectively preserves the retina in addition to the brain.

Current methods of visual rehabilitation

BACKGROUND

Despite therapeutic progress, many diseases of the eyes and visual pathways still cause persistent visual deficits that make everyday life more difficult in many ways. Rehabilitation aims to compensate for these limitations by optimizing residual vision. The demand for visual rehabilitation will increase markedly in the near future.

METHODS

We summarize the state of the art in visual rehabilitation on the basis of a selective review of the literature, including randomized, controlled trials (RCTs) in the Cochrane and PubMed databases as well as Cochrane reviews. We also pay particular attention to studies illustrating an important principle or a clinically established method.

RESULTS

Central visual field defects impair reading. Persons with an absolute central scotoma can regain reading ability by eccentric fixation and text magnification. Many kinds of magnifying visual aids are available. Specific reading training can further improve reading speed. Peripheral field defects impair orientation. Persons with a concentric field defect can be helped by tactile aids, such as a cane, and with orientation and mobility training. Persons with hemianopia can benefit from compensatory saccadic training.

CONCLUSION

Suitable rehabilitative measures chosen after the thorough diagnostic evaluation of a visual impairment and analysis of its effects can usually restore reading ability, improve orientation, and thereby enhance the patient's independence and quality of life. As the demand for visual rehabilitation is increasing, steps will need to be taken to make it more widely available. Furthermore, as the scientific basis for visual rehabilitation is currently inadequate in some areas, more research in the field will be needed.

Rehabilitative techniques

This chapter deals with neuro-ophthalmological diseases at different levels of the afferent visual pathways with special regard to visual field defects, their functional impact, and their rehabilitation. The nature of these impairments and their significance for activities of daily living can be quite varied; an exact assessment of the residual function is required to determine specific rehabilitation approaches. Rehabilitation aims to compensate for the visual deficits by means of specific training and visual aids. Visual field defects in the center cause reading disability. Preconditions for reading are a sufficient size of the reading visual field or perceptual span and sufficient resolution of the retinal area used for reading. In central scotoma, as in macular or optic nerve disease, reading ability can be regained by eccentric fixation plus text magnification. In hemianopia, reading depends on the amount of sparing in the center, the side of the defect, and adaptive strategies. Field defects in the periphery cause orientation and mobility problems. In constricted fields, tactile training with a cane is indicated; in hemianopia, explorative saccadic training is effective. With the appropriate technique, rehabilitation can be very successful, and quality of life can be regained in most patients.

Birth weight deviation and early postnatal growth are related to optic nerve morphology at school age in children born preterm

The aim of this study was to evaluate the influence of early and later postnatal growth variables on optic disc morphology in children (n = 53) born at gestational age <32 wk. On fundus photographs taken at a median age of 5.4 y, the optic discs were evaluated using digital image analysis and compared with those of a control group (n = 203). The results were analyzed in relation to gestational age, birth weight (BW) SD score (SDS), IGF-1 weight at postmenstrual age 32 wk (SDS), and weight, length, and head circumference (SDS) at follow-up. The preterm children's optic disc and neuronal rim areas were smaller than in the control group. Low BW (SDS) and weight at wk 32 (SDS) were associated with larger area of the optic cup and reduced neuronal rim area. Preterm children with known brain lesions (n = 6) had significantly larger cups than preterm children without known brain lesions. The association found between both low BW and poor early growth and later reduced neuronal tissue of the optic nerve indicate that early weight gain is important for neural development in preterm children.

Temporal visual field defects are associated with monocular inattention in chiasmal pathology

PURPOSE

Chiasmal lesions have been shown to give rise occasionally to uni-ocular temporal inattention, which cannot be compensated for by volitional eye movement. This article describes the assessments of 46 such patients with chiasmal pathology. It aims to determine the clinical spectrum of this disorder, including interference with reading.

METHODS

Retrospective consecutive observational clinical case study over a 7-year period comprising 46 patients with chiasmal field loss of varying degrees. Observation of reading behaviour during monocular visual acuity testing ascertained from consecutive patients who appeared unable to read optotypes on the temporal side of the chart. Visual fields were evaluated by kinetic (Goldmann) and static (Octopus) techniques. Five patients who clearly manifested this condition are presented in more detail. The results of visual field testing were related to absence or presence of uni-ocular visual inattentive behaviour for distance visual acuity testing and/or reading printed text.

RESULTS

Despite normal eye movements, the 46 patients making up the clinical series perceived only optotypes in the nasal part of the chart, in one eye or in both, when tested for each eye in turn. The temporal optotypes were ignored, and this behaviour persisted despite instruction to search for any additional letters temporal to those, which had been seen. This phenomenon of unilateral visual inattention held for both eyes in 18 and was unilateral in the remaining 28 patients. Partial or full reversibility after treatment was recorded in 21 of the 39 for whom reliable follow-up data were available. Reading a text was affected in 24 individuals, and permanently so in six.

CONCLUSION

A neglect-like spatial unawareness and a lack of cognitive compensation for varying degrees of temporal visual field loss were present in all the patients observed. Not only is visual field loss a feature of chiasmal pathology, but the higher visual function of affording attention within the temporal visual field by means of using conscious thought to invoke appropriate compensatory eye movement was also absent. This suggests the possibility of 'trans-synaptic dysfunction' caused by loss of visual input to higher visual centres. When inattention to the temporal side is manifest on monocular visual testing it should raise the suspicion of chiasmal pathology.