Role of Visual Evoked Potential in children with developmental delay and its correlation with Neurodevelopmental Outcomes: A Systematic Review.

Dr Neha Thorbole ^*, Dr Rasika Bharaswadkar¹, Dr Shradha Salunkhe², Dr Sheuli Paul³, Dr Shailaja Mane⁴

 

1. Associate Professor, Department of Pediatrics, Dr. D Y Patil Medical College, Hospital & Research Centre ; Dr DY Patil Vidyapeeth, Pune, Maharashtra, India.

2. Professor, Department of Pediatrics, Dr. D Y Patil Medical College, Hospital & Research Centre ; Dr DY Patil Vidyapeeth, Pune, Maharashtra, India.

4. Professor, Department of Pediatrics, Dr. D Y Patil Medical College, Hospital & Research Centre ; Dr DY Patil Vidyapeeth, Pune, Maharashtra, India.

*Correspondence to: Dr Neha Thorbole, Post Graduate Student, Department of Pediatrics, Dr. D Y Patil Medical College, Hospital & Research Centre ; Dr DY Patil Vidyapeeth, Pune, Maharashtra, India.

Copyright.

© 2025 Dr Neha Thorbole. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: 23 Dec 2024

Published: 18 Jan 2025

DOI: https://doi.org/10.5281/zenodo.14711090

Introduction

Developmental delay in children is a significant concern, as it can have long-lasting implications for their cognitive, physical, and social well-being (1) (Daugherty & Moran, 1982). Developmental delay occurs when a child does not achieve developmental milestones compared to peers of the same age range. The degree of developmental delay can be further classified as mild (functional age < 33% below chronological age), moderate (functional age 34%–66% of chronological age), and severe (functional age < 66% of chronological age). A significant delay is defined as performance that is two or more standard deviations below the mean on age-appropriate standardized norm-referenced testing (2).

Visual dysfunction is a common comorbidity in children with developmental delay, with various ocular manifestations, including refractive errors, strabismus, and vision disorders (2,3). An impaired visual function can further compound these children's developmental challenges, as vision is integral to their ability to explore, learn, and interact with the environment (4). 

Visual processing and integration are crucial for a child's overall development, underpinning various cognitive, motor, and social skills. There exist few tools to evaluate the visual status of young children. Visual Evoked Potential is an objective and reliable tool that can assess the functional integrity of the visual pathway, from the retina to the visual cortex, and has been used to study the neurodevelopmental outcomes in children with developmental delays (2,3,4,5). VEP testing is a simple, non-invasive, and easily accessible tool for evaluating the visual status of young children who might be uncooperative. It can provide valuable insights into the functional integrity of the visual pathway and visual cortex (2,3,6).

VEPs have been used as an alternative method to assess visual acuity in non-verbal infants. VEPs are the expression of the electrical activity of the visual pathways up to the optic nerve to the calcarine cortex. The measurement of VEP is made possible by applying electrodes on the scalp in the occipital region and administering visual stimuli to a patient with open eyes. Depending on the characteristics of the stimulus, pattern visual evoked potentials can provide different information on the functionality of the various sectors of the visual field and the integrity of the optical pathways. This type of instrumental exploration has a clinical application in ophthalmological retinal pathology and neurological pathology related to the optic nerve and/or brain (inflammatory, atrophic, toxic, tumoral, and genetic disease (7).

Several studies have evaluated the utility of VEP in assessing visual function in children with developmental delays, and its correlation with long-term neurodevelopmental outcomes (8). VEP is an integral part of visual function evaluation. Purposes of VEP in Pediatric Patients - Quantification of visual impairment in children suffering from visual disorders. It also has the potential to monitor children at risk for visual complications as sequelae of therapy, drug side effects, or as a result of disease complications. VEP can effectively differentiate visual impairment from visual inattention in infants. Serves as a confirmatory test for detecting visual function impairment or loss. It acts as a prognostic tool for visual and systemic recovery (9).

 

This systematic review aims to gather and synthesize evidence to address these questions:

1- Is VEP a potential assessment tool for detecting developmental delay in children?

2- Is early detection of neurodevelopmental delay possible by measuring VEP responses in children?

3- How accurate is VEP in detecting minute neurological changes directed towards developmental delay in both infants and children?

4 – What is the current evidence on the role of Visual Evoked Potential in evaluating visual pathways and its correlation with neurodevelopmental outcomes in children with developmental delay?

 

Materials & Methods

The present systematic review is a comprehensive analysis of prognostic and diagnostic prediction studies on VEP. This study's reporting adheres to the PRISMA guidelines (10).

Inclusion and exclusion criteria

Inclusion Criteria: (1) Articles published in English; (2) Full-text articles; (3) Study designs – Case-control, cross-sectional, longitudinal, retrospective, cohort study; (4) VEP as an assessment tool for neurodevelopmental outcome in children with developmental delay; (5) VEP assessment as one of the major outcomes; (6) Study population – neonates/ preterm infants/full-term infants/ children/ toddlers.

Exclusion criteria were: (1) meeting abstracts, review articles, or editorials; (2) animal studies; (3) VEPs for communication, e.g. for the brain–computer interface (4) higher-level event-related potentials; (5) VEPs used to measure thresholds other than spatial frequency, e.g. contrast sensitivity, stereo acuity, vernier or hyperacuity, color or motion thresholds; (6) studies using Evoke related potential (ERP); (7) developmental delay due to congenital viral infections eg- Zika virus; (8) study types – case report, case studies, review (narrative, scoping and systematic).

Search strategy

A comprehensive literature search was conducted using multiple electronic databases, including PubMed and MEDLINE to identify relevant studies published from inception to the present.

 

Data collection and extraction

Two reviewers (R1, R2) independently and systematically searched PubMed and MEDLINE for studies published on VEP in children for assessment of developmental delay. MeSH terms or equivalent keywords were (“VEP” or “visual evoked potential” or “visual evoked cortical potential”) and (“developmental delay” or “motor delay”) and (“children” or “infants” or “toddlers”). Review articles or other pertinent articles pertaining to VEP in the assessment of developmental delay were noted separately to capture and compare their conclusions. The following data items were extracted: bibliographic details (name of authors, the year of publication, and country), type of VEP used, the definition of delayed VEP, details of the study population (age, systemic condition/ disorder if any present), the definition of the study objective (diagnostic or prognostic), study outcomes measured. Any differences or disagreements were resolved by discussion and consensus of two reviewers (R1, R2).

 

Risk of Bias

The risk of bias is not assessed, as there is no standard outcome measure being compared: the greatly heterogeneous nature of the included studies precludes meaningful comparison of quality. However, factors such as type of study, number of subjects included, type of developmental delay assessed, and tools/methods employed for assessing developmental delay have been qualitatively discussed.

 

Results

The literature search yielded [34] studies that met the inclusion criteria. The systematic revealed a significant correlation between visual evoked potentials and neurodevelopmental outcomes in children with developmental delays. Specifically, children with abnormal visual evoked potentials were likelier to exhibit poorer cognitive, motor, and language development than those with normal.The included studies highlighted the potential of visual evoked potentials for early identification and monitoring of developmental delays.

 

Study selection and Data extraction

The search results and process of selecting articles are shown in Fig. 1. Titles and abstracts were screened to identify potentially eligible studies for inclusion. Where necessary, the full text was reviewed to determine whether a study met the inclusion criteria. Data were extracted from included studies (Fig. 1) using a standardized template. Extracted information included: study design, participant demographics, details of VEP stimulation, acquisition and analysis, details of any concomitant behavioral acuity tests, and main findings. Inclusion/exclusion decisions and data extraction for each study were independently reviewed by two reviewers (R1 and R2), and any conflicting decisions were resolved through discussion.

After the literature search, a total of 571 articles were identified. Studies that were duplicated (n = 220) were excluded. A total of 351 articles were screened for title and abstract. Out of these 317 articles were excluded for not meeting inclusion criteria. A total of 34 articles were screened for full text. Articles were excluded for the following reasons: a) full text unavailable (n= 11); b) VEP as an assessment tool is NOT a major outcome (n= 11); c) Children with normal VEP are inclusion criteria (n= 1); d) No developmental delay assessed (n=1).

 

Fig. 1 PRISMA diagram illustrating systematic review process of literature search, screening, inclusion, and exclusion

Source: Page MJ, et al. BMJ 2021;372:n71. doi: 10.1136/bmj.n71.

This work is licensed under CC BY 4.0. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/

 

Citation for PRISMA Flow Diagram - Haddaway, N. R., Page, M. J., Pritchard, C. C., & McGuinness, L. A. (2022). PRISMA2020: An R package and Shiny app for producing PRISMA 2020-compliant flow diagrams, with interactivity for optimized digital transparency and Open Synthesis Campbell Systematic Reviews, 18, e1230. https://doi.org/10.1002/cl2.1230

 

Characteristics of relevant studies

A detailed summary of the included studies is provided in Tables 1,2 and 3, with each table showing the Authors and Year, Sample size, underlying disease/ disorder, assessment methods, type of study (Table 1), Definition of Delayed VEP latency, Outcomes, Parameters used to measure outcomes and Aim (FVEP related) (Table 2), Parameters evaluated, Tools for evaluation, Delay in VEP latency/ lowered amplitudes, Aim (PRVEP related) (Table 3).

 

Of the 10 studies included in the systematic review, 5 used Flash VEP (11,15,17,19,20), and 5 used PRVEP (12,13,14,16,18) (Figure -2). All of the studies have been published before 2020 except for 1 study which was recently published in 2021. Regarding the regions of relevant articles, out of 10 studies, 4 were conducted in Asia (China =2, Korea= 1, Japan=1), 2 in Europe (Sweden =1; Scotland = 1), 3 in North America (Canada=1; USA=1, Los Angeles=1), 1 in United Kindom (London =1).

 

Figure 2 – Distribution of Flash and Pattern VEP among included studies

FVEP – Flash Visual Evoke Potential; PRVEP – Pattern Recognition Visual Evoke Potential

 

Table 1 – Characteristics of studies included in the systematic review

Authors and Year	Sample size Age /Mean age (Yrs/months/weeks)	Underlying Disease or disorder	Assessment methods/tools	Type of Study
Kim J et al (2018) (11)	N = 322 Age = younger than 42 months	developmental disorder (mental and psychomotor delay)	Bayley Scales of Infant and Toddler Development second edition (BSID-II) and flash VEP	Retrospective
Cartier C et al (2014) (12)	N = 150 Age = 10-13 years	visual processing	PRVEP	Cross-Sectional Study
Tremblay E et al (2014) (13)	N = 74 Healthy Preterm and Fullterm infants Age - 3, 6, or 12 months (corrected age for premature babies)	Visual Maturation [Parvocelllular (P) and Magnocellular (M) system maturation]	PRVEP	Cross-Sectional Study
Mercuri E et al (1998) (14)	N = 46 Age = 5 months   Follow up age = 6, 9, 12 and 18 months	Maturation of visual function in full-term infants who suffered hypoxic ischaemic encephalopathy (HIE) at birth and/or who presented with lesions on neonatal brain imaging	PRVEP   (PH -VEP OR – VEP)	Longitudinal study
Kato T et al (2005) (15)	N = 135 (Preterm infants) Age =	cystic periventricular leukomalacia (PVL)	Flash VEP, Cranial Ultrasonography, EEG	Cross-Sectional
Feng JJ et al (2011) (16)	N = 102 (LBW and VLBW infants) Age = 4-6 yrs	Visual perceptual and visual-motor impairments	pattern reversal visual evoked potential (PRVEP)	Case-Control study
Feng JJ (2010) (17)	N = 77 (LBW, VLBW and full term) Age = 23 to 25 months/ 2 year	Visual cognitive function	Flash visual evoked potentials (FVEPs)	Cross-Sectional study
Varcin KJ et al (2016) (18)	N = 34 Age = 11–16 months	Tuberous sclerosis complex (TSC)	PRVEP	Cross-Sectional study
Thordstein CM et al (2004) (19)	N = 54 Age = gestational age of 40 and 46 weeks	brain function in infants with intrauterine growth retardation	Flash VEP	Case-control study
Shepherd AJ et al (1999) (20)	N = 81 Age = 1- 3 days Follow-up age = 3, 6, and 12 months	Genetic or prenatal abnormality	Flash VEP	Longitudinal study, Case-control study

 Table 2 – Characteristics of included studies utilizing Flash VE

Authors	Definition of Delayed VEP latency	Outcomes	Parameters used to measure outcomes	Aim (FVEP related)
Kim J et al (2018) (11)	P100 >115ms	developmental delay in both mental and psychomotor domains	MDI, PDI, and DQ scores lowered in delayed VEP latency group	Flash VEP as an Early indicator of developmental delay in both mental and psychomotor domains
Shepherd AJ et al (1999) (20)	N3 > 372 ms	Survival and Development of CP	At-risk preterm infants survival – Flash VEP Sensitivity – 86%; Specificity – 89%   Development of CP - Flash VEP Sensitivity – 60%; Specificity – 92%	Prognostic value of Flash VEP concerning severe neurological outcome in preterm infants from birth to term age Sensitivity and specificity of flash VEP concerning survival and development of CP (cerebral palsy) in at-risk preterm infants
Feng JJ (2010) (17)	P2= 149.65±23.79 ms	correlation between visual cognitive functions and FVEPs	MDI and visual cognitive capability Lowered with delay in P2 main wave latency	As a noninvasive and convenient method, FVEPs are useful in assessing certain aspects of an infant's visual development and visual function.
Kato T et al (2005) (15)	N300 in Type A or N300a in Type B >330 ms	periventricular cysts formation, Acute and/or chronic stage EEG abnormalities	The mean duration from the appearance of absent VEP to cyst formation was 12 days (range 3–20 days), to abnormal EEG findings – the duration range is 1- 8 days	Flash visual evoked potential (VEP) findings and their chronological changes in preterm infants with cystic periventricular leukomalacia (PVL) during the early neonatal period
Thordstein CM et al (2004) (19)	P latency >200ms	Brain function	P latencies were negatively correlated to Neonatal anthropometrics (birth weight, birth length, head circumference, and to the leanness score) P latencies were negatively correlated to Prenatal blood flow velocities/pulsatility index	VEP as a prognostic instrument for early identification of those with intrauterine growth retardation who will suffer from neurodevelopmental difficulties

DI - mental developmental index (MDI) and the psychomotor developmental index (PDI)

DQ – Developmental quotient

P100 - the first positive waveform

CP – Cerebral Palsy

 

Table 3 - Characteristics of included studies utilizing PRVEP

Authors	Parameters evaluated	Tools for evaluation	Delay in VEP latency/ lowered amplitudes	Aim (PRVEP related)
Feng JJ et al (2011) (16)	verbal, performance, and overall intelligence quotients	WPPSI, PRVEP at five levels of spatial frequency (checkerboard pattern (check) sizes of 108′, 54′, 27′, 13′ and 7′)	P100 amplitudes were lower in the below order – VLBW< LBW< Normal children	PRVEP may provide an objective and convenient measurement in detecting the problem of visual perception in children
Mercuri E et al (1998) (14)	maturation of cortical function	ORVEP and PHVEP square wave gratings (black and white stripes) at an oblique orientation	mildly delayed VEP in focal infarction or haemorrhages   abnormal VEP responses in hypoxic-ischaemic encephalopathy grade 2 and 3,  involvement of the basal ganglia, cerebral palsy	VEP as prognostic indicators of the maturation of cortical function in a population of fulllterm infants with brain lesions on neonatal MRI
Tremblay E et al (2014) (13)	differential maturational changes in the Magnocellular (M) and the Parvocellular (P) visual pathways	PRVEP -. Stimuli were two low spatial frequencies (0.5 cycles per degree [cpd]) presented at two Michelson [9] contrasts (10% and 95%), and one high spatial frequency (2.5 cpd) at 95% contrast	Lowered PI and N1 amplitudes in preterm infants	Role of specific VEP paradigms in evaluating the impact of premature birth on visual development
Varcin KJ et al (2016) (18)	visual reception skills/ visual cortical processing	PRVEP	No delay	utility of phase reversal VEPs as readouts of visual cortical processing in TSC
Cartier C et al (2014) (12)	visual processing impairment on p,p’-DDE exposure, both pre- and postnatally, during early childhood	PRVEP Vertical sinusoidal gratings with a spatial frequency of 2.5 cycles per degree were presented using Presentation® software (Neurobehavioral Systems, Inc. San Paolo, CA) at a reversal rate of 1.1 Hz 7 at four visual contrasts from high to low visibility, i.e., at 95, 30, 12 and 4%	Both increase and decrease in VEP amplitudes increased N150 amplitude at the lowest contrast(4%) N75 amplitude at mid-contrast (30 %) was significantly decreased with increasing p,p’-DDE plasma concentration at age 5	VEP responses associated with p,p’-DDE exposure

Wechsler Preschool and Primary Scale of Intelligence (WPPSI)

Tuberous Sclerosis Complex – TSC

 

Findings of the studies

The studies show that delay in VEP latency is correlated with negative neurological/ development outcomes. Only one study measured the sensitivity and specificity of VEP (FVEP) in predicting survival and development of cerebral palsy (20) (Table 2). Most of the studies support the use of VEP as a prognostic indicator of developmental delay. The flash VEP has been greatly used in infants compared to toddlers or preschoolers (11,15,17,19,20).

 

There is a great diversity in the population of included studies (Figure 3) . The study population with the disorder showed some kind of abnormal VEP response. The majority of them showed delayed VEP responses that showed both clinical and statistical significance. The delay in VEP latency has been an indicator of abnormal response and negatively correlates to developmental delay. The absent VEP is correlated with worse neurological outcomes (P<0.05) (Figure 4).

 

Figure 3 – Distribution of diverse population among studies (percentage)

PI – preterm infants

CP - cerebral palsy

 

Figure 4 – Relationship between VEP response and study population 

Absent VEP was the most prevalent defect, occurring in 13 out of 14 infants (93%). Between day 1 and day 10 (median day 3), absent VEP initially appeared. On days 1 or 2, there was delayed latency, which was followed by absent VEP. One infant's VEPs were always normal till day 14, however on day 17, an abnormal waveform was observed. Almost all infants with cystic PVL had abnormal flash VEPs within the first 3 weeks of life, but chronological changes of flash VEP findings were seen during the period (15).

Another study assessed the prognostic value of the flash VEP; the sensitivity of the flash VEP up to term age in predicting death was 86% and in predicting CP was 60%, with negative predictive values of 99% and 96% respectively. The higher prognostic value in the present study may partly be due to the use of more precise normal ranges and the different timings of the VEP tests (20).  The VEP latencies were prolonged in the following order – VLBW> LBW > Normal; Preterm birth> Full term birth (13,15,16,17) at P< 0.05 . Meta-analysis was not possible due to the heterogeneity of the study setting and findings.

 

Discussion

VEPs are a non-invasive, objective way to measure the occipital cortex's electrical reaction after presenting a visual stimulus (15). They are especially suitable for young children and infants who are unable to comply with routine vision tests or express visual complaints. The primary goals of visual eye exams (VEPs) in pediatric patients are to: (1) identify lesions that cause dysfunction of the sensory visual pathways (the VEP is a sensitive indicator of subclinical lesions and can be used to differentiate visual impairment from visual inattention in young infants); (2) confirm functional loss when visual system disorders are present; and (3) quantify visual impairment in patients with known visual disorders, either empirically by noting the severity of the VEP abnormality to flash and pattern stimuli or by visual acuity estimation studies (early quantification of vision loss allows referral to early intervention programs, which can mitigate the long-term consequences of the disability); (4) keeping an eye on patients who may experience visual complications as a result of illnesses like hydrocephalus or neurofibromatosis, or as a side effect of treatments like neurosurgery or chemotherapy, in order to identify and prevent long-term effects on the developing nervous system; (5) determining the prognosis for visual and systemic recovery based on flash VEPs for particular pediatric disorders, such as perinatal asphyxia in full-term neonates, acute-onset cortical blindness, and, to a certain degree, in comatose children; and (6) occasionally, helping with the differential diagnosis (21).

To the best of our knowledge, this is the first systematic review to assess the utilization of VEP in assessing developmental delay in children.  The current literature consists of a systematic review of VEP pertaining to visual acuity in the elderly (22). The present systematic review stands out to be the only one assessing developmental delays with a heterogeneous population like TSC, Brain lesions, VLBW, LBW, and preterm and full-term infants and children exposed to chemicals. The included studies had participants ranging from infants to toddlers/children. A wide spectrum of

Visual evoked potentials (VEPs), especially the N1 and P1 components, can be used to examine the preferential activations of the M and P systems in prematurely born infants to look into the likelihood of changed visual system activity (15). In both the mental and psychomotor domains, children with visual impairment confirmed by VEP have a greater developmental delay. VEP has some clinical utility even though it offers little information. VEP investigations could be readily used for children with probable developmental delays when a doctor is concerned about visual impairment. Additionally, the results of the VEP study may shed light on children's development and act as early warning signs for the need to see an ophthalmologist about an existing issue (11).

Flash VEP gives clinicians a more accurate estimate of morbidity or death by objectively assessing the integrity of the nervous system's susceptible pathways (20). The flash VEP anomaly is linked to the highest likelihood of serious neurological sequelae in preterm children who are clinically "at risk." On the other hand, a normal flash VEP indicates a favorable neurological prognosis even in preterm infants with several clinical risk factors (20). Absent VEP at any age in both healthy and diseased individuals is an indicator of negative neurological outcomes and signifies developmental delay. Prolonged VEP latencies –N1, N2 N3, N150, N300 in Type A or N300a in Type B, P100, P1, P2 negatively correlate with neurological outcomes (11,12,13,14,15,16,17,18,19,20).

The flash VEP has been greatly used in infants compared to toddlers or preschoolers. In the neonatal stage, a flash visual evoked potential is thought to be superior to a pattern arrangement. This response's intracerebral propagation most likely depends on subcortical circuits (23). P latencies correlated linearly to late prenatal flow velocities indicative of a blood flow redistribution as observed in intrauterine growth retardation and to neonatal anthropometric measurements. Human newborns with disproportionate growth retardation exhibit delayed brain maturation as indicated by visual evoked potential latencies. At least up to 46 weeks of GA, this effect can be seen. Authors hypothesized that this technique could be a prognostic tool for early identification of those with intrauterine growth retardation who will experience neurodevelopmental difficulties because different individuals with the condition have varying degrees of impairment in their visual evoked potential recordings (19).

A critical element to obtaining accurate results with FVEP is finding the ideal time to use FVEP for predicting and assessing children's neuromotor outcomes requires collecting data during the critical period of visual development in both preterm and full-term infants (20).

According to reports, children's visual evoked cortical potentials grow in two stages: a rapid phase that lasts from birth to roughly six months, and a slower phase that continues until adolescence [38]. Significant waveform shifts from a single positive peak to a negative–positive complex in response to pattern reversal stimuli were seen during the early fast phase (24). Waveform development occurs at the same time as synapse development and the morphological development of the macula and myelin sheath. During this time, it was also seen that the latencies of the main positive peaks for larger tests gradually decreased to the adult level. Furthermore, P100 grows more quickly for large checks than for tiny checks, according to research on VEPs' reactions to pattern-reversal stimulation. Preterm children's smaller receptive fields have underdeveloped neural connections that readily transmit low spatial frequency information (25). According to the preceding data, the visual system for spatial processing in the two groups of preterm preschoolers may not be as advanced as that of the full-term control group. Additionally, despite the fact that the VLBW children's cognitive profiles did not differ substantially from those of the LBW children, the delayed maturity was particularly evident for them (16). . Timely ophthalmologic assessment mediated by the use of VEP in preterm infants is of great significance as it directly correlates to the possibility of early and timely intervention (11). 

 

VEPs are a greater predictor of abnormalities associated with the Magnocellular pathway compared to the Parvocellular pathway (13). The retinocortical visual stream, which is mostly composed of the magnocellular and parvocellular circuits [13,26), mediates vision immediately after birth. There are anatomical and physiological differences between these two pathways. The magnocellular circuit is most sensitive to higher temporal and lower spatial frequencies and reacts to lower brightness contrasts. It is unique to fast motion processing and peripheral vision. The parvocellular pathway is particularly sensitive to higher spatial and lower temporal frequencies and reacts best to greater brightness contrasts. The parvocellular pathway is unique to color and form perception and central vision [27].

According to several lines of evidence, the magnocellular pathway develops more quickly and is present earlier than the parvocellular pathway. The magnocellular system grows more quickly throughout pregnancy and the first few months of life than the parvocellular pathway, according to anatomical research in rhesus monkeys and humans(28,29,30,31).

It is hypothesized that VLBW children may have more magnocellular pathway deficiencies than parvocellular pathway deficiencies. Additional evidence that suggests the magnocellular stream may be more compromised than the parvocellular stream indicates that early abnormal visual experience primarily impairs the visual functions that mature at the fastest rate during the injury period (13). PRVEPs help assess certain aspects of visual development and visual function.

One of the study findings implies that, for evaluating high-risk newborns, both PH and OR VEP are valuable diagnostic and prognostic instruments. They appear to offer more comprehensive information on the general maturity of cortical activity and the overall outcome across cognitive and motor domains, in addition to being a sensitive indicator of the maturation of particular components of visual function (14).

Only study did not find any abnormal VEP response in TSC children. The findings support the utility of phase reversal VEPs as readouts of visual cortical processing in TSC and suggest that delays in more complex visual skills in TSC may not be rooted in deficits in the processing of basic visual information (18). Except for differentiating between pre and post-chiasmal lesions, abnormalities of flash and/or pattern VEPs are typically not specific to the kind or precise location of the lesion.

 

Future directions

1. More research is required to determine the mechanism underlying the visual perceptual ability delays linked to preterm delivery.

2. Longterm studies with larger sample size need to be conducted  to compare the visual functions of preterm and full-term children. 

3. To determine the evolutionary changes of flash VEPs in preterm children with PVL, more research involving a greater number of PVL newborns with serial flash VEP recording right after birth is required.

4. To find out if the M system finally recruits the parietal region or if it develops improperly, not recruiting these dorsal regions, more source analysis studies in older children are required to examine the M route deficit in preterm infants,

 

Conclusion

VEPs are becoming a vital tool in pediatric neurology and ophthalmology. Given the challenges of evaluating the visual system's function in young or sick children and the VEP's sensitivity to subclinical impairment in this area of the central nervous system, they will most likely play a bigger part in the future. Given the limitations of systematic review, VEPs stand out to be good prognostic markers for the early identification of neurodevelopmental outcomes in children with developmental delay that paves way for early screening and intervention.

 

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