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Your Child Needs a Eye Examination!
When?
Children should have a comprehensive vision examination before the age of three, and another exam before the child begins school. Because children grow fast, their eyes also change quickly, so it is appropriate that they be examined each year after that
If vision problems go undetected, there can be a profound effect on the process of learning and the child's success in school. Unfortunately, many vision problems aren't detected early because children think everyone else sees the same way they do, and they don't usually complain.
Do not rely on school vision screenings to detect vision problems.
What to Expect
While a vision exam can vary widely based on the age of the child, most of the key points are the same.
(Note: for the purposes of this article, we will use the pronoun "he" to refer to the child being tested, but that is only for convenience, not because the testing will be different for girls than for boys.)
You may help your child by reassuring him that getting his eyes tested is mostly fun, and doesn't hurt at all. In fact, most children find getting a vision exam really is fun and interesting.
First, the eyecare practitioner will need to ask for some information regarding the child's personal health and the family history, both for general health and for ocular disease. This is because many eye conditions do run in families.
If the child has had a previous examination or a vision screening, please bring that information with you for the eyecare practitioner to review. Changes in the eyes and with a child's vision happen relatively quickly, but the more information that is available, the better the practitioner will be able to review his or her findings and point out any differences.
Many times, children don't complain or ask questions about their vision because they think everyone else sees the same way they do, but if your child has had difficulties in pres-school, kindergarten or elementary school, please share that with the eyecare practitioner, too.
The Vision Examination
After reviewing the family history, the first test will be to establish how well he sees by testing his visual acuity. For preschool-age children, the doctor may use pictures instead of letters, but these are standardized to represent the same sizes of the letters that would be used for older patients. Each eye will be tested separately, at 20 feet and at reading distance.
Parents may wonder how it is possible to determine whether a child needs vision correction when he is too young to be able to answer questions about it, but in fact it is relatively easy, using an instrument called a retinoscope. The retinoscope is mounted on a handle and is made in such a way that the EP can look through it while shining its light across the pupil of the eye. The light is reflected back from the retina, in much the same way as an animal's eyes reflect the light from an automobile headlight; by evaluating how much and how fast the reflected light moves, it is possible to determine whether there is a refractive error and what lenses will correct it. The person being tested doesn't need to say anything at all.
Stereoscopic vision and the ability to appreciate 3-dimensions are tested by using a set of 3-D glasses. The child is asked to choose the 3-D image from among a series of pictures. Very young children may be asked to "touch" the tips of the wings of a fly which is presented in three dimensions; the wings will usually appear to be floating above the image presented. Different versions of these tests are available, so the child may be asked to touch the tips of the antlers of a large deer, for example.
A type of stereoscopic viewer may be used in conjunction with special cards to test whether the child is using both eyes at the same time, and roughly how they line up together.
Eye muscle coordination is tested by asking the child to follow a moving light in a set pattern to make sure the ocular muscles are working correctly, in each eye separately and then together. The ability to track a moving target accurately is important in reading.
Peripheral vision, or vision off to the sides, can be tested by asking the child to pay attention to a small toy or light, then bringing in another object and taking note of how far off to the side the child notices it. This is a test done on each eye separately.
Alignment and aiming of the eyes is tested by having the child look at a small object, then covering one eye and removing the cover a few times to see if the other eye moves when the first is occluded. Then, the paddle is moved from one eye to the other several times while the child is still looking at the toy, to test whether there is a tendency for the eyes to cross too much or diverge too much.
Colour vision testing is done using a set of Ishihara plates in a booklet. Each plate in the booklet is covered with coloured dots, and will contain a number made of dots of a slightly different colour hidden within it. Each eye is tested separately here, too. Small children may be asked to use a soft, dry paintbrush or similar tool to trace the figures hidden within the plates if the child doesn't yet know his numbers.
To check for a normal response of the pupils to light is checked by dimming the lights in the room and watching carefully to see if each pupil contracts in response to a light shining in it, and opens up (dilates) when the bright light is removed.
To evaluate the health of the anterior segment, or the front of the eye, the doctor will use an instrument called a biomicroscope, or slit lamp. He or she will check for anything unusual in the front part of the child's eyes, including the eyelids, lashes, tears, conjunctiva, cornea and iris, and the crystalline lens behind the iris. By using a hand-held lens in conjunction with the slit lamp, it is also possible to view parts of the retina and optic nerve.
The health of the structures located in the interior of each eye will be checked using another instrument called an ophthalmoscope to see the retina and the head of the optic nerve.
Usually, the eyecare practitioner will use drops in the eyes to dilate the pupils for a better look, but this isn't necessary for all young patients. One effect of dilating the pupils is that the drops used may temporarily remove the ability to focus the eyes, which is useful for the doctor to re-check for refractive errors with the retinascope.
A Word About School Vision Screenings
Sometimes, a school vision screening catches a child with a vision problem; more often, however, their value is questionable at best.
When the screening is done by eyecare practitioners or ophthalmic technicians, it can be of value, but when performed by teachers or parent volunteers, screenings will usually catch only one or two types of vision problems: myopia (nearsightedness) and high astigmatism. The reason for this is that the vision is checked by having each child read from an eye chart across the room. Children who are farsighted or have lower amounts of astigmatism can usually do that easily.
Having good vision across the room is necessary, but many school screenings don't test for how well the eyes work as a team, or how they track a moving object, both of which are skills needed to be a good reader. Some screening protocols don't test the vision up close, where the child holds reading material or his computer monitor.
The risk of screening by non-professionals is that if the child doesn't fail the screening, his parents may feel there is no need for a comprehensive vision exam. Relatively simple problems like uncorrected hyperopia (farsightedness) can cause the child to lag behind his peers and have serious long-term consequences.
We applaud the efforts of parents, teachers and other school officials to do what they can, but vision problems can easily hide behind a school screening that doesn't find anything wrong.
Unless your own eyecare professional has done the screening, please don't take the results seriously.
Results
By all these methods and tests, a complete picture of the health of the eyes, their ability to see clearly, how they align and work together, how they move, how well they track, colour vision and neurological health has been constructed. Even without the child answering any questions, there is a lot of information that can be gathered.
If there is a need for corrective lenses or any other treatment, it is better to know earlier rather than later, because problems in any of these areas can interfere with learning and development.
Parents wouldn't think of sending their children to school without the proper supplies, clothing and other equipment needed to participate in the learning experience, and they would make sure he eats a good breakfast after getting enough sleep the night before. Having his eyes and vision examined, too, is just good, common sense.