Eye Development Milestones

Excerpt from Eye Development Milestones : Introduction to brain development milestones

In order to first understand what goes wrong in neurodevelopment we need to have a working understanding what normal development looks like. We will begin at prenatal/birth milestones and progress through completed development.

As you have discovered in Fixing the Brain Book 3, there are two basic functions in the brain; receptive (input) and expressive (output). For this article we are limiting our discussion to three main receptive functions; vision, hearing and tactile (touch) functions and also we are discussing the three corresponding expressive functions of mobility, language and manual functions.

The receptive and expressive functions develop in predictable order and times in child development. An aberration in development at any level of one function will ultimately affect any subsequent developmental milestones above the aberration. Globally, this aberration in one developmental function also affects collateral functions. For example, a problem in visual development will ultimately affect language and mobility development. Challenges in auditory function affect language and mobility and so on.

This writing is not designed to give you the exact week, month or year of age that a milestone is reached in normal development but rather to acquaint you with the developmental order and interplay of the milestones. If you are caring for a child who has not developed an avenue of function appropriately it is more important to find out where the development got off track and mush less important to know when it should have developed. We simply understand where it went wrong and complete that function and move on.

The goal is to find and fix the problem in the development of the child.

This find and fix heart-set is critical when dealing with developmental disorders, delays and injuries in either the child or adult. With this model of neurodevelopment you can identify the completed and the incomplete milestones to discover where the first developmental aberration in any function occurred. Identifying the lowest level of dysfunction is the first step to fixing all developmental shortfalls and disorders. 

Caveat: Not included in these pages on the model of neurodevelopment is accelerated function. The section of neurodevelopment we are concerning ourselves with is the one that is sandwiched between prenatal and accelerated/advanced function. In other words, we are covering from birth to completed “normal” development specifically. Some of the other avenues of neurodevelopment not specifically outlined here are; global academic, emotional development, social development, smell, taste, gnostic, intuitive and instinctive functions.

Visual development

Vision is a receptive (input in) function of the brain. Its main counterpart in expressive function correlates to mobility. Mobility functions have a greater impact and influence on visual development than the other functions. Vision development is not limited to affecting and being affected by mobility but also carries an impact in manual, language, academic and emotional development. Globally, visual function also affects social, instinctive and even smell and taste development and perception.

  • The muscles, nerves and brain parts connected to the eyes have more than one billion delicate parts which must work together to provide clear vision.
  • The visual system takes up less than 2% of the body by weight, yet it consumes 25% of the nutrients the body takes in.

Although the physical eyes and neuropathways begin developing in early fetal development, visual development does not take off until light and environmental objects to view become available at birth. Present at birth, there will be basic reflexes like pupil response, flinch reflex and some faint outline perception of images but with no real cognitive sight developed.

Visual development starts out slower than the other receptive functions of hearing and tactile development simply because there is very little stimulation for the eyes in the womb. Because of a lack of light for image contrast, lack of depth in the environment and the lack of changing landscape, this limits the opportunities for neuropathways to develop until after the infant is born and introduced to environmental light along with changing scenery and environmental images.

Pupil reflex at birth

In neurodevelopment, the pupil reflex is an automatic brain/eye response to light that every newborn should have. Pupil reflex is influenced by hormones like adrenaline, emotional responses, cranial nerve development and environmental toxins. The most sensitive muscles in the human body are in the eye. Toxic environmental burdens in the body can show up by affecting these muscles and causing an irregularly shaped pupil. Adrenal dysfunction can cause either a slower-than-normal or an unsustainable pupil response.

Even before birth, the pupil response to light develops in the brain and eyes at about twent-seven weeks of gestation As the baby is developing in the womb, the eyes have little opportunity to develop as there is limited light, depth and changing shapes available to stimulate them. Once outside of the womb the newborn’s eyes now receive adequate light and newfound opportunity to develop sight.

The pupils constrict or dilate in response to light. When the brain receives signals from the nerves in the eye that tell how much light is entering the eye, the brain then produces the pupil reflex when it sends a parasympathetic response signal to the pupil’s sphincter muscles in the eye. These sphincter muscles are the ones that constrict and dilate the pupil’s opening.

A constant biofeedback to the brain regulates the amount of light that enters the eye by constricting or dilating the pupil of the eye. Any delayed or abnormal pupil response to light affects the subsequent levels in eye development of outline detail perception, central detail vision and beyond. Additionally, it will affect speech development, motor control and reading. This occurs because the eye/brain connection does not regulate the light input for the accurate reception and interpretation of images falling on the nerves in retina of the eye. This causes dulled images, inattentiveness to detail, visual sensory integration issues and light sensitivities.

Adrenaline produced in the sympathetic flight or fight situation, will dilate the pupil to give a wider field of vision and heighten sensitivity to peripheral movements and dangers. In the case of prevarication, or the telling of lies, the pupils will normally constrict. After habitual prevaricating the pathological responses to lies eventually retrain both pupil response and other body language responses to not react at all but to remain constant as if the truth was being told.

A difference in the size of the pupils from one eye to the other, called Anisocoria, can indicate one or more of several things that can be wrong. Things like injured cranial nerves, inappropriate development of lower levels of lateral brain/eye development, brain insult or brain injury, toxic chemical insult, potassium deficiency, and even parasites in the gut. If either of the pupils is not perfectly round but have jagged edges or are misshaped, this is an indicator of a toxic liver burden.

Outline perception, reflective smile

The next stage of eye development after pupil reflex is outline perception and reflective smile. Outline perception is the ability to see definitions of contrast starting at birth with more extreme contrast of light and dark developing to that of black and white and finally to the detail perception of discerning the subtle contrasts in similar colors, which completes the stage of outline detail perception.

While the baby is nursing, the outline perception develops as the baby begins to discover the mother’s face. At first the mother’s face is only a vague silhouette but quickly becomes shades of contrasts giving basic shapes to the face. The baby can smell, taste, feel and hear the mother up to now and starts to integrate these senses with the eyes to recognize the mother visually. This development occurs in first one eye then the opposite eye as the baby is rotated from one breast to the other.

For instance: When the nursing child is suckling on the breast, one eye is occluded by the breast and the other eye, closer to mommy’s face, is being stimulated with input. Soon the baby is recognizing the mother’s outline and facial features. So, if the baby is on the left breast, the right eye is closest to mommy and receives the majority of the stimulation. When the baby is rotated to the other breast, the eyes alternate and now the left eye is the one receiving input.

The brain first develops outline detail perception laterally (one side and then the other) and at about 16” or roughly the distance between the babies face and the mother’s face while nursing. This distance is an optimal distance throughout the life of the child through adulthood for the visual input of symbols and words, reading and learning in general. It is good to remember that 16” is the optimal distance for introducing images for visual memorization of vocabulary words and also for some visual therapies.

The eyes do not coordinate very well at this stage of outline detail perception as the brain is developing laterally and the brain will not coordinate the eyes together completely until the next stage of eye development. It is critical to note at this point that babies that are bottle fed and only held in one arm of the parent and not rotated from side to side do not develop brain organization appropriately. This will cause one eye to be much stronger than the other eye and can cause mild to severe brain disorganization and strabismus.

The mirror neurons in the cerebral cortex are also developing at this point of outline detail. When you smile, the baby smiles, when you frown—they frown. This developmental stage of reflective smile is the foundation for emotional responses, mimicking language, reaching for items, basic survival skills and a host of other adaptive activities that develop rapidly in the infant. Reflective neurons are critical for early survival of animals in the wild.

Mirror neurons are highly reactive to heavy metals like aluminum and mercury which happens to be adjuvants in childhood vaccines. A metals-sensitive child will regress neurologically with each vaccine it receives. Sometimes the effect of heavy metals on the developing brain can be permanent and sometimes the effects fade in a few weeks or months. Spacing out vaccines and waiting for further brain maturation can be wise choices. For some children, any vaccine at all can be neurologically devastating.

Central detail vision and hands play

Central detail vision or macular vision occurs in the macula of the eye. In anatomy, this is the small yellowish area of the retina near the optic disk that provides central vision. When the gaze is fixed on any object, the center of the macula, the center of the lens, and the object being viewed are in a straight line. In the center of the macula is a depression, called the fovea. The fovea contains specialized nerve cells that are known as cones. Cones are associated with color vision and perception of fine detail. 

Because the macula is the fine detail vision center of the eye this is where the brain eventually learns to interpret symbols into meaning. At later stages of development this is where reading occurs best and math is processed best. Reading and symbol recognition are simply visual memorization of images taken into the eye, recognized, analyzed and stored in the brain.

To experience the central detail vision and its importance let’s consider the temporary flash blindness associated to photography flash. The macula can be over-stimulated with too much light causing the brain to “tune it down” the macula. This occurs in the case of flash-blindness. We all have experienced temporary flash blindness with the flash of the camera in our eyes. This causes the “blue dot” in our vision for a few minutes because the brain reacts to the flash by tuning down that portion of the macula thereby leaving the “blue dot”.

In the case of “red eye” in a photograph, the macula of the eyes reflects the flash of light from the camera back to the camera film causing what is known as “red eye” in the photo. The newest cameras have a pre-flash built in to over-stimulate the macula of the eye before the flash that takes the picture thus reducing red eye in the ensuing photograph.

Children who have under-developed macular vision live life with the “blue dots” (actually a gray or fuzzy blotch) in the center of the vision all the time. This child will not look you in the eyes, sit really close to the television screen, and will read while holding a book at a very odd angle. It’s like taking a pair of opera glasses and painting over the lenses. Everything in front of becomes unrecognizable and you have to rely on the peripheral vision to navigate and read.

If there is a challenge in central detail vision the brain will have difficulty recognizing and memorizing symbols and words. The child may even skip whole lines while reading and invent words that it cannot see clearly using adaptive function to compensate for the lack of detail vision. This child will also be hyper-peripheral and distracted by motions in the periphery of the vision often bringing with it a diagnosis of “distractible”.

Central detail vision is the stage where the eyes first begin to really work together bilaterally. The brain begins to recognize the information as the same in both eyes and basic tracking begins to occur. Depth perception moves forward here as the visual horizons open up to the baby’s developing mobility and playing with its hands while the eyes begin to triangulate objects.

Mobility

Simultaneously at this stage of eye development the baby is rolling over, scooting around and viewing objects and movements in the horizon. If the baby is not accomplishing these mobility milestones it will affect the visual development. As depth perception opens up the baby will begin to reach out and find objects. The primary grasp develops here also in manual function as the baby discovers depth and reach.

Depth perception and basic eye tracking

Distance and depth perception happen by way of accommodation from the pupil’s ciliary muscles which change the position of the lens of the eye to focus on the desired object. These muscles are closely aligned with and affected by the sphincter muscles of the eye that regulates light input to the nerves of the eye. Problems in pupil reflex can cause problems in depth perception simply because of the proximity of these two muscles.

Depth perception is a matter of triangulation. To visually determine distance accurately, the eyes are the required two fixed positions viewing and reporting a common third position whether it is mobile or stationary. It takes both eyes fixed and focused on the same object for appropriate depth perception. Depth perception is especially critical when tracing objects coming straight at the body.

At this stage of depth perception and basic eye tracking development, the baby is learning where its body is in relation to objects and movements around it. The baby is beginning to see clearly enough and with depth perception enough to start picking up objects with its pincer grasp rather than the whole handed primary grasp.

Depth perception and eye tracking are critical for later acquired reading skills. Not only do the eyes need to focus clearly on the symbols for accurate interpretation but they need to track smoothly as the child reads. Mobility development of belly scooting and crawling army style help the eyes to focus on the horizontal level and begin to track both stationary and moving objects.  Smooth pursuit eye movements allow the eyes to closely follow a moving object. It is one of two ways that visual animals can voluntarily shift gaze, the other being saccadic eye movements.

Pursuit differs from the vestibulo-ocular reflex, which only occurs during movements of the head and serves to stabilize gaze on a stationary object. Most people are unable to initiate pursuit without a moving visual signal. The pursuit of targets moving with velocities of greater than 30°/s tend to require catch-up saccades. Smooth pursuit is asymmetric: most humans and primates tend to be better at horizontal than vertical smooth pursuit, as defined by their ability to pursue smoothly without making catch-up saccades. Most humans are also better at downward than upward pursuit. Pursuit is modified by ongoing visual feedback.

Eye dominance, recognizing environmental symbols and coordinated eye tracking

Note: a majority of the baby’s horizontal tracking develops during previous stage and vertical tracking completes development at this stage of eye development in perfect timing with mobility hands and knee crawling. This occurs as the child sees the hands moving in the vertical line of the peripheral vision.

At this level of eye development, the child will be in the early stages of emerging brain hemisphere dominance and hand dominance for manual function. The predisposed right- handed child should be beginning to prefer the right eye as dominant and the predisposed left-handed child should prefer the left eye. Very important: Never influence the emerging hand dominance in a child but rather let the child choose naturally.

Recognition of environmental symbols will be emerging now. A high chair, for example becomes the recognized place for feeding. A baby food jar equates to food and the child will physically jump, make noises and salivate in anticipation of the food when objects of feeding are presented. A day care sign or even the infamous “golden arches” of MacDonald’s Restaurant will now be recognized as places of interest.

Photos of specific people will strike the interest of the child and pictures or drawings of animals on flashcards will be recognized when the child is instructed as to the name of the person or animal. Even before the child can speak 200 words, they will be able to pick out pictures when asked to find a certain animal or person among several flashcards.

Eye tracking becomes smooth and the eyes coordinate together until a tracked object reaches about an inch and a half from the bridge of the nose. A ball rolled from several feet away and at a moderate pace toward the child can be tracked with the eyes and effectively captured by the child’s hands. When reaching for objects the child will start to prefer picking up smaller objects or food items with the dominant hand. As the child becomes more proficient with the depth and reach coordination they will do so more and more with the pincer grasp (thumb and forefinger) instead of with the primary grasp (whole hand or both hands).

Entire words can now also be recognized in visual memorization by flashing the word on a flashcard. These words are not recognized phonetically or as alphabetic combinations but rather as a whole picture. For instance: Because reading is visual memorization the word “elephant” becomes one piece of information as word. It does not take phonetic skills to interpret the word “elephant” once the word is stored in memory. When you show the child the word “elephant” and they learn the sound of the word associated with it, from then on the brain automatically tells them what that word means every time they see it.

Symbol recognition and basic reading skills

Once little eyes see and recognize the letter “A” and then catalogs it in the appropriate brain center, brain remembers it every time it sees the letter “A”. Recognition of numerals is the same thing. Show the eyes what the numeral is and tell the ears what sound goes with the numeral and the child remembers it. This is called visual memorization.

Chains of information form as blocks of information i.e. the alphabet sequence of A-Z and numerical order of 1-10. The same principle of visual memorization in the previous level of Environmental The concept of simple alphabet combinations to make up words begins to form as the brain develops more complex abilities.

At this point the word recognition capacity of the child to learn new words is limited only by the amount of input given to the child. The child gains a growing capacity to memorize thousands of words as they are visually made available.

Basic reading skills depend on a large data base of words forming in the child’s memory. Once memorized the words to the child’s favorite book can be recognized one at a time and appropriately understood and spoken by the child. A new book can be introduced and “read” word by word if the child has previously seen the words on a flashcard and memorized them.

Complex reading skills

Unlike visual memorization of words, complex reading skills includes phonetic skills. Phonetic interpretations and enunciation of visually seen symbols making a word are a concept and dependent upon sequential processing abilities. Until a child can visually process 6 sequences, that is; see a sequence of items, store them in the brain and retrieve them in order, the child will have undue difficulty with phonetics.

We typically send the child to school to learn math and reading skills at the age of about 6 years old. This is the neurodevelopmental age of 6 sequences where concepts form and are understood. In complex reading skills, alphabet letter combinations can now be sounded out and word meaning extrapolated from the context of the newly sounded out word.

Reading comprehension skills develop rapidly in this stage as the child begins to see pieces and whole blocks of information as they relate to pieces and blocks. The child can absorb reading sequences, overall meaning, implied meaning and relate them back verbally, with visual expression (i.e. acting out a story) in written form.

See also Cross Eye and Eye Development for natural solutions to eye crossing and strabismus

Authored by Neurodevelopment Consultant Craig Stellpflug NDC, CNC, Healing Pathways Medical Clinic Scottsdale, AZ Copyright 2009 Craig Stellpflug© Permission is hereby granted to copy and distribute this article but only in its entirety

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