How does one check that the child’s eye is developing properly?
The eye has two basic abilities: (1) Raw sight or colour and black white vision with all its attendant abilities to see in the light and dark. (2) Ability to locate and fix on an object, thus simultaneously changing focus and judging an object’s distance and depth.
In a child, both the function of its eye and the extent of development of the eye have to be tested separately. (A child is usually born hypermetropic with a small plus number, around +3.00. By the age of four, the eyeball grows, and the number vanishes). The ability to judge the extent of vision, depends on symbol recognition and an appropriate response following recognition.
Obviously you cannot ask a new-born baby what and how it sees, and hence all tests are indirect, based on neurologic evaluation of the rate of development. Nevertheless during the last few years with the rapid advance of the science of photo-electronics, the understanding of the new-born eye has progressed rapidly.
What are the neurologic movement tests done to check the development of the eye in a child?
The neurologic tests are done by seeing the movement of the eye under certain conditions. Each movement indicates a functional eye mechanism with a balanced neurologic component.
The earliest movement usually present at birth is the gliding movement. When the child’s head is turned to the opposite side, the eye remains-fixed at a point in space, thus compensating for the movement. Thus, though the head may be moved by the parent or doctor, the eye will remain at a particular point and not move with the head rotation.
Optically elicited movement
Optically elicited movement is usually present in the second week of life. Any object introduced in the child’s vision will immediately attract attention to it.
After the eye fixes at an object, if the object is moved the eye continues to follow the movement. It is present at the age of 4½ months.
Acoustic (sound) elicited eye movement
If you clap your hands, the baby tries to locate the sound by sight and fixes to it, even though the object is not in its visual field. This is not developed till the 5th month of life.
This is not valid if the noise-producing movement is within its visual field in which case the much earlier elicited optical movement comes into play.
How is the vision of an eye tested?
Direct tests are difficult unless a child can respond. However by 4 months, tests can be devised to check vision.
At 4 months, a 1 inch square white block placed on grey paper five feet from the child should elicit a response from the child, when moved to and fro. Alternatively to increase contrast the block may be hung from a string against an illuminated black background.
At the age of 5 months, the child will follow the block if moved.
Though crude tests, they are important for checking that the visual ability is present in the earlier months.
When does a child need to have its eye examined and why?
The first examination should be at the age of 5 months. The macula, the area of clearest vision in the retina, develops completely by 6-8 months and hence any problems in the eye which stop light from reaching this area will stop its development and must be treated urgently before the development is complete.
The second examination should be at the age of 2 years. By this time most of the development of the eye is complete and any abnormalities can be attended to.
The third examination should be at the age of 5 years. The muscle balance is almost complete and any problem, especially suspected squint, is best treated at this age. Vision can be tested subsequently as response is now easy.
Subsequently an eye check-up every 2 years is adequate provided no problems are present.
What are the symptoms that may indicate vision problems in a child?
(1) Rubbing the eyes
(2) Closing or covering one eye
(3) Squinting while looking at the blackboard
(4) Headaches after reading
(5) Tilting the head to one side
(6) Holding reading material very close to the eye
(7) Moving the head instead of the eye while reading
(8) Puffy eyelids, especially in the evening
(9) Persistent letter or word reversal
(10) Confusing similar words
(11) Frequently leaving out words while homework is copied from the blackboard
(12) Drop in school grades after 3rd standard
(13) Persistent motion (car or train) sickness
(14) Blurring of vision at any time.
The visual causes of many of these symptoms are not picked up in a typical school screening test. Therefore the value of the screening is limited and should never be construed to be a vision examination.