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ORIGINAL ARTICLE
Year : 2020  |  Volume : 28  |  Issue : 1  |  Page : 9-13

Cortical Visual Impairment in Children − Aetiology, Clinical Findings and Neurological Findings


1 Department of Pediatric Ophthalmology and Strabismus, Sankara Eye Hospital, Bengaluru, Karnataka, India
2 Sankara Eye Hospital, Bengaluru, Karnataka, India

Date of Submission01-Jan-2020
Date of Decision21-Apr-2020
Date of Acceptance23-Apr-2020
Date of Web Publication07-Sep-2020

Correspondence Address:
Dr. Sowmya Raveendra Murthy
Department of Pediatric Ophthalmology and Strabismus, Sankara Eye Hospital, Bengaluru, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njo.njo_1_20

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  Abstract 


Objectives: To evaluate the demographic profile, aetiology, systemic and ocular associations and findings on neuroimaging, of children with cortical visual impairment (CVI) at a tertiary eye hospital in South India. Materials and Methods: Records of 85 children with CVI, undertaking visual stimulation therapy (VST), were retrospectively analysed between March 2016 and March 2018. The data obtained was analysed for the age and gender profile, aetiology, cycloplegic refraction, fundus evaluation, MRI findings, pre and post visual stimulation therapy vision. Other associated ocular and neurological abnormalities were also noted. Results: The records of 63 boys and 22 girls were analysed. The mean age was 1.93 years with 58.8% aged <2 years were analysed. Hypoxia ischemic encephalopathy (HIE) was found to be the most common aetiology (31.7%), followed by epilepsy (27%) and structural abnormalities of brain (24.7%). Amongst the ocular associations, refractive error was the most common, seen in 42 (49.4%) children, while strabismus (exotropia>esotropia) in 40 (47%), nystagmus in 34 (40%) while pale disc in 31 (36.5%) patients. Fifty-five(64.7%) children had associated developmental delay, while 40 (47%) had seizures. Other neurological associations noted were, cerebral palsy (14.1%), microcephaly (14.1%), hearing loss in 5 and hemiparesis in 1 patient. MRI abnormalities were present in 65 (76.4%), with ischemic encephalopathy (32.9%) being the most common change noted. Conclusion: In our study cohort, HIE was found to be the most common cause of CVI, with refractive error and strabismus being the common ocular associations, while seizures and developmental delay were the common neurological associations. Neuroimaging showed that the structural insult was at both the cortical and white matter levels.

Keywords: Cortical visual impairment, developmental delay, exotropia, ischemic encephalopathy, HIE, nystagmus, refractive error


How to cite this article:
Murthy SR, Sudhakar P. Cortical Visual Impairment in Children − Aetiology, Clinical Findings and Neurological Findings. Niger J Ophthalmol 2020;28:9-13

How to cite this URL:
Murthy SR, Sudhakar P. Cortical Visual Impairment in Children − Aetiology, Clinical Findings and Neurological Findings. Niger J Ophthalmol [serial online] 2020 [cited 2021 Jan 19];28:9-13. Available from: http://www.nigerianjournalofophthalmology.com/text.asp?2020/28/1/9/294377




  Introduction Top


According to the recent global estimates, there are 19 million visually impaired children in the world.[1],[2] Of these, 1.26 million are blind with a vast majority living in developing countries.[1],[2] Statistics have shown that in up to 60% of childhood cases, visual impairment is treatable or preventable.[2] These numbers and figures stand to rationalize the control of childhood blindness as one of the priorities of Vision 2020: The Right to Sight. Unlike in adults, the risk of amblyopia in this segment of population only adds to the gravity of the problem at hand. Hence, dealing with various causes of visual impairment in children is of paramount connotation.

The revamping of perinatal care and intensive neonatal care services have not only increased the survival of babies, but also of those born prematurely and with hypoxic‑ischemic insults and perinatal stress. This is of significance as perinatal injury to the developing visual system is a common cause of visual impairment and neurologic morbidity in children.[3],[4] Cerebral or cortical visual impairment (CVI) is one such entity.

The definition of CVI has evolved to encompass a significant deficit in visual and perceptual visual impairments resulting from dysfunction, anomaly or injury to retro-geniculate visual pathways (optic radiations, occipital cortex, and visual association areas) and oculomotor control in the absence of major ocular disease, oculomotor disorder, or uncorrected refractive error.[5] Hence, the diagnosis of CVI should not be made in the presence of concurrent pathology of the anterior visual pathway.

While there have been reports of large series of patients with CVI in developed countries, there is paucity of studies from developing countries like India. This disparity could perhaps be accounted for by the possibility of underestimation, missed diagnosis and under reporting of these cases, due to various reasons such as lack of complete awareness, lack of screening facilities, or even failure of documentation of the same. Hence, recognizing CVI, which is the first step toward rehabilitation and prevention, entails modifications in the examination techniques towards detailed assessment of vision and the components of visual function. It has been stated that as many as 65% of patients with CVI may have associated ophthalmological abnormalities.[6] Refractive errors and strabismus are common associations.[7],[8] As part of the syndrome, structural anomalies such as cataract, coloboma, optic atrophy, and retinal dystrophy have also been found to be associated.[9],[10] ROP may be found to be in association with periventricular white matter injury.[11] Optic nerve hypoplasia and optic atrophy known to occur with a wide range of brain disorders including CVI, impair visual function.[12] Disorders of eye movement control, including strabismus, nystagmus, unstable fixation, inaccurate fast eye movements (dysmetric saccades), deficient smooth pursuit movements, and paroxysmal deviations, in which the eyes intermittently deviate upward (most commonly) are common in children with CVI.[11]

The extremely nascent age and the associated ocular co-morbidities make their examination difficult. However, more importantly, the lack of adequate facilities for paediatric eye screening and the lack of compliance thereof, adds to the challenge. The purpose of this study was to look at the common causes, and the ophthalmic associations and neuroimaging findings of CVI in a south Indian cohort. This could help us address the potential areas which when identified could possibly bridge the existing lacunae in effectively tackling this emerging dilemma.

Methods

We retrospectively reviewed the clinical records of eligible children registered for the vision rehabilitation clinic at our hospital, between March 2016 and March 2018.

Our study included children aged <16 years with a confirmed diagnosis of CVI and excluded incomplete records. The diagnosis of CVI was based on an ocular examination that revealed poor visual function bilaterally that could not be accounted for by age, structural ocular examination findings, optic atrophy, or high refractive error. Preliminary comprehensive eye examination of these children was done in the pediatric ophthalmology department.

The digital medical records (DMR) of the hospital helped us procure pertinent data. Following the demographic data, which included age and gender, we made a note of relevant birth history. This included stormy perinatal course, use of supplemental oxygen and its duration, ventilator support, anemia requiring transfusion, repeated episodes of hypoglycemia, which could be an indicator of sepsis, neonatal enterocolitis, phototherapy for hyperbilirubinemia, seizures, meningitis, or encephalitis.

Visual responses in infants and young children who could not identify letters or pictures had been qualitatively assessed by their quality of fixation and following. The former was noted as being brief, sustained, uncertain, or inaccurate while the latter by the child’s ability to follow toys, with eyes alone or eyes and head together or only with the head, the last two suggesting possibility of poor vision. We broadly classified and documented these responses as:
  1. Inability to fixate or follow light
  2. Ability to either fixate or follow light
  3. Ability to fixate and follow the light


In older children, the quantitative records (Lea paddles, Snellen optotypes) were considered.

We then noted the findings of dynamic retinoscopy performed at 33 cm using a streak retinoscope with the object of interest presented to the child and noting

the accommodative response, and then switching the child’s fixation to a distant target (at least 3 m) like a lighted mount on the wall and back again to the near.

Pupillary examination performed with a moderately bright torch light with dimmed room light, was looked for and any note of paradoxical pupils or relative afferent pupillary response was included in the data. Anterior segment examination findings of associated anomalies, if any, such as a developmental cataract or other media opacities, done using either a portable slit lamp or distant direct ophthalmoscopy, were recorded. Data on the documented findings on dilated fundoscopy especially optic atrophy were also collected. Other findings such as scars in the macula, altered background pigmentation, and arteriolar attenuation, suggestive of coexisting retinal dystrophy, were also noted.

The findings of cycloplegic refraction done preferably using homatropine 2%, were also noted.

General examination findings noted in case records of dysmorphic features, change in gait, or other systemic features suggestive of syndromic association were noted.

Further, findings of MRI brain reports in the records were studied and the positive findings recorded.


  Results Top


Records of 85 children, diagnosed with CVI, were reviewed. Of these, there were 63 boys and 22 girls. Majority of them (58.8%) were <2 years of age, with mean age of 1.93 years [Table 1].
Table 1 Age distribution of the children with CVI

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Though many of the patients (37.6%) had multiple aetiologies, hypoxic ischemic encephalopathy (HIE) was the most common (31.7%) followed by epilepsy (27%). The remainder had various aetiologies as listed in [Table 2].
Table 2 Aetiology of CVI among the children

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The ocular and neurological associations in our patients are summarized in [Table 3] and [Table 4]. Ocular findings were present in almost all the patients, with significant refractive error (>-2/+2 Ds) being the most common (49.4%) followed by strabismus (47%). Of the 40 patients with strabismus, majority (23) had exotropia. Nystagmus was seen in 40 patients. Fundus examination revealed that 47 of the 85 children (55.2%) had normal fundi, 28 had disc pallor (33%) and 1 had optic nerve head hypoplasia. 44 of the 85 patients had multiple neurological deficits. The common neurological findings were developmental delay (64.7%) followed by seizures (47%). Cerebral palsy and micro/brachy/scaphocephaly were seen in 14% each. Amongst the less common associations were hearing loss (6%) and hemiparesis (2%).
Table 3 Ocular co-morbidities in the children with CVI

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Table 4 Neurological associations in the children with CVI

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All the patients had neuroimaging (MRI) done, and the findings are listed in [Table 5]. Abnormality in MRI was seen in 77.6% and non-specific changes in 22.4% of cases. The most common findings were ischemic encephalopathy (32.9%), periventricular leukomalacia (15.3%), and structural abnormalities (12.9%).
Table 5 MRI findings in the children with CVI

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The visual function of these children during their preliminary evaluation was recorded as:
  1. Ability to either fixate or follow light
  2. Ability to either fixate and follow light
  3. Inability to fixate or follow the light


We found that majority of them (39 of 85 children) only followed light, while 22 could fixate and follow the light, while the remainder 24 children could neither fixate or follow the light.


  Discussion Top


With the new wave of revamped perinatal services sweeping across developing countries like India, CVI is looming ahead as one of the important causes of acquired bilateral visual impairment in children. The availability of limited literature on children with CVI, and more so from the developing world, it becomes even more imperative to study the nuances in identifying the disorder. CVI is a verifiable visual dysfunction which cannot be attributed to disorders of the anterior visual pathways or any potentially co-occurring ocular impairment.

The most common associated aetiologies in our series of children (most of whom were <2 years old) were hypoxic ischemic encephalopathy (31.7%), followed by epilepsy (27%) and structural abnormalities of the brain (24.7%). This was comparable to the results of a few similar studies. Huo et al. reported that the four most common causes of CVI were perinatal hypoxia (22%), cerebral vascular accident (14%), meningitis (12%), and acquired hypoxia (10%).[6] While Khetpal et al.[14] reported perinatal hypoxia (35%), prematurity (29%), hydrocephalus (19%), structural central nervous system abnormalities (11%), and seizures (10%) as the common aetiologies. Many children (69%) had multiple aetiologies. Pehere et al.[11] found perinatal hypoxia to be the most common aetiological association.

Majority (77 of 86 children, i.e. 89.5%) of the children in our cohort had associated neurological issues, of whom 55 had delayed developmental milestones. This perhaps corroborates the fact that most of these children had a neurological insult as an antecedent event. The associated neurological deficits were reported to be in all patients to some extent and ranging between 65.3–75% in various studies.[6],[14],[15],[16] In our study, we found that developmental delay (64.7%) was the most common neurological association followed by seizures (47%), cerebral palsy (14.1%), and microcephaly (14.1%). This was comparable to the finding from a similar study in the Indian subcontinent, by Pawar et al.[17], who found developmental delay and seizures to be the most common neurological associations. However, the statistical results of Huo, Good, Hoyt, Khetpal et al. though grossly analogous, varied in the order of frequency. Seizures followed by cerebral palsy were found to be the major neurological association.

This could possibly be due to one of the following causes viz.,

Our study being retrospective in nature, possible lower reporting of seizures in our cohort or possibly a higher chance of being missed due to absence seizures manifesting in other subclinical forms and its documentation in records.
  1. Sample size being smaller and the difference in population compared (eastern versus western population).
  2. The higher incidence of meningitis/encephalitis in other studies could also account for higher incidence of seizures in their study.
  3. Difference in terminologies used may also be an explanation . Some studies have overlapped inclusions of features of developmental delay and traits of cerebral palsy to be included into one single entity of cerebral palsy unlike ours.


Apart from neurological issues, children with CVI can have a myriad of ocular manifestations.[13] All the children had associated ocular comorbidities, with 62.8% having multiple associations. The results from our study highlighted that the major causes of visual impairment were those amenable to treatment like refractive error (96.5%) and strabismus (exotropia > esotropia) (46.5%). While this was true for the majority, the ones more refractory to treatment, like optic atrophy (36%) and nystagmus (39.5%), also contributed to the spectrum. This was in conjunction with findings from similar studies by Khetpal and Pehere et al.[11],[14] in which, refractive errors, strabismus, and optic atrophy, in the descending order of frequency, were found to be the most common ocular associations.Most of the records of patients had MRI of brain reports, of which 12 were normal, while the vast majority (86%) had abnormalities in the report, of which 21.6% had multiple changes. Ischemic encephalopathy (32.5%) was the most common change, followed by some non-specific changes (22%), PVL (15%), and structural abnormalities (12.8%). Ischemic encephalopathy, followed by PVL, cortical and subcortical atrophy and structural malformations were the most common MRI changes in other studies.[14],[17]

The visual function of these children revealed that majority of them (45.9%) only followed light, while 25.9% could fixate and follow the light, while the remaining 28.2% children could neither fixate nor follow the light.

Our study included 85 patients less than 16 years and majority (58.8%) were <2 years of age, with mean age of 1.93 years. There were 63 boys and 22 girls. Khetpal et al.[14] included 98 patients ranged from 0.2 to 19 years, with an average age of 3.1 years. There were 56 males and 42 females. Pehere et al.[11] included 428 severely visually impaired children aged ≤3 years with average age at presentation being 14.02 months. There were 264 (62%) boys and I64 (38%) girls. Males were commonly affected in both studies comparable to our cohort.


  Conclusion Top


Cortical visual impairment has ocular and neurological associations. In our study cohort, majority were boys and aged less than 2 years. HIE was found to be the most common cause of CVI, with refractive error and strabismus being the common ocular associations, while seizures and developmental delay were the common neurological associations. Neuroimaging showed that the structural insult was at both the cortical and white matter levels.

This may suggest the need for early ocular examination in children with history of hypoxic ischemic encephalopathy or developmental delay to detect the possible cortical visual impairment in these children.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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