Indira Rengarajan, M.Optom, FLVC

Occupational Optometrist, Occupational Optometry Services, Sankara Nethralaya, Chennai, India



Over the years, the survival rates of children with Neurodevelopmental Delay (NDD) and other perinatal adverse events have increased with the help of extensive high-quality treatment options. Yet, the prevalence of NDD conditions including Cerebral Palsy (CP), Autism Spectrum Disorder (ASD), Intellectual Disability (ID), Attention Deficit Hyperactivity Disorder (ADHD), Visual Processing Dysfunction such as Cortical Visual Impairment (CVI), and visual impairment among children are also parallelly increasing as a threat to public health. (1)

Developmental delay affects an estimated 10% of India’s 15 lakh new-borns. If not treated promptly, this might result in permanent cognitive, hearing, and vision impairments. (2)

 NDD is defined as a child’s underdeveloped or immature response and neurological system at a specific stage of development. The nervous system’s immature growth and development interfere with perceptual skills, hand-eye coordination, visual functioning, and motor skill development. (3)

 Neural networks of the visual system:

The visual system is a complex network that includes ocular and subcortical components as well as several brain areas, including higher-order parietal and frontal areas. Children will suffer from a variety of issues, ranging from lower-order visual sensory and oculomotor deficits to difficulty with higher-order visual perception. Common symptoms include difficulties orienting and maintaining visual attention, detecting, and seeing certain visual elements (e.g., colours, shapes, movements), as well as providing meaning to what is viewed, and employing the visual input to guide behaviour. These visual processing functions, for example, visual identification and visuospatial orientation, might be thought of as prerequisites for higher-order visual perception processes. (1)

 Critical periods for early intervention:

The human brain is not fully formed at birth and continues to develop until the age of 20 years, it is completely dependent on experiences and is modified and shaped by them during the critical periods. For instance, in people who are born blind, the areas of the brain that normally process visual information are rewired to begin processing sounds, including language. The critical period is a maturational period during which a critical experience has its greatest impact on development or learning, resulting in typical behaviour that is adapted to the specific environment to which the brain has been exposed which will have reduced or no effect after this period. (4)

Early intervention:

Given the number of children with visual loss and developmental difficulties in India, and on the other hand, considering the critical periods of brain development there is an urgent need to scale up early intervention programs. (2)

Early access to intervention remains a significant challenge in India due to several factors, including a lack of awareness among families and professionals, a lack of trained professionals; a lack of tools and resources to serve the entire population; and a lack of access to services for children from rural areas because the majority of early intervention centres are urban based. (2)


Early intervention followed by identification during the critical periods (< 3 years of age) plays a pivotal role in the child’s development in case of special clinical conditions.


Neurodevelopmental delay, early intervention, visual developmental therapy



  1. Kooiker, M. J., van der Linden, Y., van Dijk, J., van der Zee, Y. J., Swarte, R. M., Smit, L. S., … & van der Steen, J. (2020). Early intervention for children at risk of visual processing dysfunctions from 1 year of age: a randomized controlled trial protocol. Trials21, 1-14.
  2. Jayaraman, D., Jacob, N., & Swaminathan, M. (2021). Visual function assessment, ocular examination, and intervention in children with developmental delay: A systematic approach – Part 2. Indian journal of ophthalmology69(8), 2012–2017.
  3. Aldharman, S. S., Al-Jabr, K. H., Alharbi, Y. S., Alnajar, N. K., Alkhanani, J. J., Alghamdi, A., … & Almallah, A. (2023). Implications of Early Diagnosis and Intervention in the Management of Neurodevelopmental Delay (NDD) in Children: A Systematic Review and Meta-Analysis. Cureus15(5).
  4. Mundkur, N. (2005). Neuroplasticity in children. The Indian Journal of Pediatrics72, 855-857.