Eye and vision development

Definition

The visual system is the most complex sensory system in the human body. However, it is the least mature system at birth. Though they have the anatomical structures needed for sight, infants have not learned to use them yet. Much of their first weeks and months are spent learning to see. As children grow, more complex skills, like visual perception, develop.

Description

At birth, the sense of hearing is much more dominant than the sense of sight. Normal visual development is the change from just responding to simple brightness or high contrast, toward the organization of details into patterns and the ability to apply meaning to an object or picture.

Infancy

At birth, babies are capable of seeing shapes by following lines where light and dark meet. They can see variations of light and dark and shades of gray. Newborns can only focus between 8–12 inches (20–30 cm), so much of their vision is blurred. Full-term babies should be able to see their mother's facial expressions within a week of birth.

Eye muscle coordination in a newborn is also very immature. Babies' eyes often turn in or out or do not work together, a condition called strabismus . Babies initially learn to focus their eyes by looking at faces. They then gradually move out to objects brought close to them. Tracking and eye teaming skills begin to develop when infants start following moving objects. This usually happens by three months of age. Brightly colored moving objects, such as a mobile, can help stimulate visual development. Babies then start to learn how to coordinate their eye movements. At four months of age, babies can see the full range of colors. Between four and six months, the child normally begins batting at or reaching for the mobile or toys held in front of him or her.

During the first three to six months, the retina is fairly well-developed, and babies can visualize small objects. Depth perception also develops. By six months of age, the eye has reached about two-thirds of what will be its adult size. At this stage, the two eyes are most likely working together. The result is good binocular, or two-eyed, vision. It is during the first year of life that the eyes' greatest physical development occurs.

As babies start controlling their own physical movements, their eye/body coordination develops. By the fourth or fifth month, babies' brains have finished learning how to blend the images coming in from both their left and right eyes into a single image, with strong depth perception. Spatial and dimensional awareness keep improving as the baby learns to aim accurately when reaching for objects. Babies at this age also learn to change focus quickly and accurately between near and far distances.

A child's clarity of vision (visual acuity) has usually developed to 20/20 by the time the child reaches six months of age. At this time, babies achieve fairly precise eye movement control. At ages eight to 12 months, babies are judging distances well. Their eye/hand/body coordination continues to evolve, allowing them to grasp and throw objects with some accuracy. The integration of their fine motor abilities and their vision permits the child to manipulate smaller objects, and many begin feeding themselves. Once children begin to walk, they learn to use their eyes to guide and manage their bodies' large muscle groups to direct their whole movements.

Infancy

The following timeline discussion highlights some of the developmental milestones of vision development in a child's first year. Between birth and one month, a baby shows preference for familiar faces and objects, pays attention to the human face for short periods of time, has acuity of about 20/400 but can detect a black line on a white background that is only 1/16 of an inch (1.6 mm) wide, and possesses color vision, with the exception of blue.

At two months, a baby will visually lock onto a human face, watches people who are some distance away, is able to alternate his or her gaze between two people or objects, and demonstrates simple visual preferences.

Between four and six months, a baby is enthralled with other baby's faces, and he or she enjoys looking in a mirror. At this age the baby recognizes a person on sight and smiles. The baby also shifts from preferring what is familiar to that which is new, with the exception of people. The child will also look for objects when they fall from view.

From six to 12 months, a baby continues to "see" objects even when they are no longer visible. At this age, the baby also responds to words a parent uses to label familiar objects and people, by gazing in their direction.

Toddlerhood

After the first year, children's eyes and vision continue to develop. Their eye muscles gain strength, and the connections between nerves multiply. This development is aided by providing visual stimulation. Activities such as stacking building blocks, coloring, and cutting all assist in improving eye/hand/body coordination, eye teaming, and depth perception. By age three, most children have developed the necessary language and motor skills that allow them to participate in some traditional vision tests.

Preschool

During the preschool years, a child's vision keeps developing. The child develops visually guided eye/hand/body coordination, the fine motor skills and visual motor skills required for reading. The following can facilitate a preschooler's visual development:

• reading aloud to the child and letting him or her see what is being read
• providing a chalkboard or finger paints and demonstrating how to use them in play
• allowing time for interacting with other children and for playing alone

School age

It is important that children have a complete eye examination before beginning school. The optometrist or ophthalmologist needs to determine if a child's vision is prepared to handle reading, writing, and other close-up activities. While toddlers use their eyes primarily for distance sight, school requires that the child's eyes focus on very close work for hours every day. This activity occasionally causes eye problems to arise. It is important to note that children rarely report vision problems. They believe their vision is normal and believe others see the way they do. The basic vision skills needed for school work are:

• near vision (the ability to see clearly at 10–13 inches [25-32 cm])
• distance vision (the ability to see clearly beyond arm's reach)
• binocular vision (using both eyes together for depth perception)
• focusing skills (the ability to keep both eyes accurately focused at the proper distance)
• eye movement skills (the ability to aim the eyes accurately)
• peripheral awareness (the awareness of objects located to the side while looking straight ahead)
• eye-hand coordination

Common problems

Infants born prematurely have more difficulty integrating and interpreting visual information even when their acuity is normal. In some cases, children develop their visual reflex later than normal. This is called visual maturation delay. A condition, nystagmus , which sometimes develops in infancy, causes the eyes to jump, dance, wiggle, or oscillate. Babies with this problem may or may not have normal vision.

KEY TERMS

Nystagmus —An involuntary, rhythmic movement of the eyes.

Strabismus —A disorder in which the eyes do not point in the same direction.

Parental concerns

Parents need to assess their child frequently for any signs that the child's visual development is not progressing as expected. Some vision disorders are untreatable at later ages, so it is important to have the child seen by an optometrist or ophthalmologist no later than the age of three.

When to call the doctor

At the first signs of eye and vision problems, parents should consult their pediatrician, optometrist, or ophthalmologist. Some of these signs are:

• an eye that is crossed far into the nasal area
• eyes turned grossly in or out or which do not move normally before the age of three months
• an eye that moves while the other remains still
• an eye that appears considerably different from the other
• the inability at three months of age of an infant to follow a toy passed in front of him from side to side

During the preschool years, parents should continue looking for signs that a vision development problem exists. These signs may include a short attention span for the child's age; difficulty with eye/hand/body coordination; or the avoidance of coloring, puzzles, and other activities.

A child should have his first eye exam by the age of three (or sooner if vision problems run in the family ), so the practitioner can assess if vision is developing normally. Vision should be checked again when the child enters school.

Some of the signs of visual problems in the school age child are:

• frequently losing his or her place while reading
• frequently avoiding close work
• holding reading material closer than usual
• frequently rubbing the eyes
• complaining of headaches
• turning or tilting the head to use one eye only

Since vision changes may occur without the parents or the child noticing them, a child should visit an eye doctor at least every two years, more frequently if specific problems or risk factors exist.

Resources

BOOKS

Marks, Paul. Through a Baby's Eyes: An Infant's Humorous Diary on the First Year of Life. Chula Vista, CA: Black Forest Press, 2004.

ORGANIZATIONS

National Eye Institute. 31 Center Drive MSC 2510 Bethesda, MD 20892–2510. Web site: <www.nei.nih.gov>.

WEB SITES

Glass, Penny. "What Do Babies See?" Vision Connection, December 3, 2004. Available online at <www.visionconnection.org/Content/ChildrensVision/AboutChildrensVision/AboutInfantsVision/WhatDoBabiesSee.htm> (accessed January 11, 2005).

Deanna M. Swartout-Corbeil, RN