The Faults of vision and the child

Child and Sight (1)

 

VISION AND CHILDREN

Although babies are born with open eyes, they hardly see anything and need to learn how to use them. This is of major importance since we acquire 80% of our knowledge through our eyes. In the first weeks of its life, the baby lives in a world of vague shadows and dim lights, After the second month, sight begins to stabilize and at three months old, the baby starts to gaze at people or objects and follow them with his eyes. He then learns how to recognize a few familiar objects in a still limited universe such as his mother's face and his bottle.

In later months, he puts out his hand to catch hold of what he sees. In the sixth month, he begins playing with objects. The capacity of the eye grows steadily and the baby learns how to extract the best from his visual system. The most important period lies between his 12th and 18th month,

We have only two eyes and must take care of them during our whole life. But, in our early years, it is the parents' responsibility.

ACCOMMODATION AND CONVERGENCE

Accommodation is much the same as focusing your camera. It is done by the crystalline lens which changes the eye's curvature. The modification is made by a muscle which provides a sharp image on the retina for various distances. Accommodation has to be learned and begins to be effective in the first weeks of life when the baby starts to gaze at objects. Convergence too needs to be learned and it is not unusual for a child to squint until 4 or 5 months old. This strabism is usually of no great importance and disappears after a few months. But if the squint is very marked a physician should be consulted.

VISUAL ACUITY The dimension of the smallest object seen at a specific distance is called visual acuity. It is very low in a small baby who lives in a world of vague shapes but he progresses rapidly and at about 6 months old has one fifth of an adult's visual acuity. This is usually measured in tenths (6/10- 10/10) or in twentieths (20/20). DEPTH AND SPACE PERCEPTION Depth perception enables the child to evaluate the distance of an object and whether it is behind or in front of another. This is done by both eyes, the images in each eye being being seen under different angles, which gives the brain a sense of depth perception. The brain merges both images to make a single image in normal binocular vision. If both eyes cannot look at the same point, there is strabism or squinting.

Binocular vision affords a wide field of vision. The performance is far more limited with only one eye. If you close one eye, the vision is less good than with both eyes. The normal field of view is of 220 to 240 degrees in a horizontal direction, but the best visual acuity is right in the centre of the field of view.

COLOR VISION

The child sees color by means of three different cells on the retina, one responding to blue, the other to green and the last to red. If one kind of cell is deficient, color vision may be diminished (dischromatopsy). 2 to 3/000 people are completely color blind or see only in black and white (achromatopsy). Some degrees of color deficiency are found in 8% of men and 0.70% of women, especially in the red or green range. At present, there is no treatment available for color deficiency or color blindness.

                    Lens for learning

                 Color Vision