The human visual system is our most dynamic sense. At birth, many of the components of the visual system are in place, such as the eyes, optic nerve and brain, but it is after birth that growth, development, co-ordination and fine tuning of the visual system occur.
Many people confuse the word “vision” and “eyesight” and think they are synonymous, but they are in fact very different. Eyesight essentially refers to the physical attributes and performance of the many organic components involved in the visual system. 20/20 vision is a commonly quoted measure of normal VISION, yet it simply describes the sensitivity of the eye to see fine details in the distance. Vision uses EYESIGHT as its foundation. Vision combines information from many sensory systems to create a perception of reality. Vision uses information from all the senses, including hearing, smell, touch and even taste, which is then combined with information provided via EYESIGHT. After all of this is processed, it is then linked to memory and an image of the world or object is created. In other words, VISION is learned, so understanding the normal visual developmental stages of an infant, through to child to even a teenager is extremely important to ensure that they acquire adequate visual performance for learning later in life. A child with a vision problem may experience learning difficulties later in life that are not necessarily related to intelligence. Intervening to provide the stimulation required to encourage more normal development of VISION is one of the goals of Behavioural Optometry. The information followed will outline some of the changes that occur in the first six months of life and the important developmental milestones to give parents an approximate indication of what to expect in their child’s visual capabilities at a particular age. Any significant delay should be referred for immediate assessment to a Behavioural Optometrist.
First 6 Months of Life
The new born eye is remarkably close to its full adult size. This is one of the reasons why a babies eyes always look so gorgeous and big, in proportion to their body size.
The visual acuity (sharpness of eyesight) of an infant develops rapidly from birth. At 1 month, the child has a visual acuity of 6/180, then reaches an adults level of 6/6 (20/20) by 4-6 months of age.
Focusing like visual acuity appears to develop to full adults level by 4-6 months of age, where there is adult capacity to vary focus and to fixate on objects at different distances.
There is a primitive reflex called the tonic neck reflex which exists at birth. This reflex allows the head and eyes to point to the outstretched hand when the head is turned to the side. At 4 months, the child exhibits “swiping” behaviour, where it sees an object and tries to grasp it, but doesn’t have the required coordination. At 6 months, the child is able to grasp an object they see.
At birth, the child’s eyes generally point in the same direction, but they do not work together as a team. This is why it is common for it to appear that there is turned eye. The eyes generally move together, but only one eye fixates at a time. By 8 weeks, the child is generally able to use both eyes as a team.
This article is continued in the article Vision Development Milestones covering the important developmental milestones from birth to 5 years of age.
Chih Chi Lee, Behavioural Optometrist Eyecare Plus 77 CecilAve, Castle Hill, NSW 2154 Tel: 02 8677 5483 www.ccleeoptometrist.com