When examining young children, begin with near testing before introducing the distance chart to the child. After near testing, say, "Let's look at the same pictures a little further away." Move the chart gradually to 3 meters (10 feet). If the child loses interest, move closer: to 1.5 meters (5 feet) or one meter (40 inches). Always test well within the cognitive visual sphere of the child, the space within which the use of vision is possible. Typically developing children at age 5 years or older may be switched directly from a near vision test to a 3-meter (10-foot) chart.
When testing recognition acuity, you need to know that the typically developing infant/child) has the concept “same” so that matching can be used, or b) has names for the optotypes and has no difficulty using the names. When testing children with atypical development, first train with the LEA 3-D Puzzle (#251600), Response Key Card (#251700), or Flash Cards (#251800). (See videos at http://www.pro-vision-dortmund.de/videos).
The child should sit comfortably on a chair. Place the test on the wall, middle of the test at the eye level of the child. Check the testing distance from the chart to the child’s eyes.
Establish a method of communication for identifying the symbols, such as pointing on the keycard (matching).or naming (signing). Matching is a purely visual test situation and thus preferred. Naming brings other functions than vision in the test situation, pronunciation of words and deciding on names. Naming is a faster test situation than matching and therefore often used in testing typically developing older children who have no problems in using names of concrete objects, ring, window, house, apple or any name that the child wants to use. If names are used, decide with the child which names will be used to identify the symbols by asking “What would you like to call this picture, and this picture ..”. All names are accepted.
Cover the beginning of the line above the line to be read with the white side of one of the 4 flash cards and ask the child to identify the first and the second symbol on each or every other line in descending order when testing binocularly, i.e. measuring the functional VA value.
Move down the chart until the child hesitates or misidentifies the first symbol and the second symbol.
Move back up one line and ask the child to identify all the symbols on that line. If the child identifies all symbols or at least 3 symbols correctly, go back to the line with smaller symbols (that were incorrectly identified). Ask the child to identify all symbols on that line. The child may have adjusted accommodation and may now read the line. In such a case, move to the next line to define the threshold. The visual acuity value written on the chart at the line of the smallest optotypes read correctly (at least 3 out of 5) is the threshold line and the binocular visual acuity value.
If the child skips a symbol, let the child complete the line and then say: “You jumped over this picture between (e.g.) ‘house’ and ball’.” What is it?” You may briefly point at the symbol to help the child find the symbol that you mentioned but do not leave your finger pointing at the symbol. Pointing helps fixation and thus improves VA.
After obtaining good responses with binocular testing, proceed by testing each eye separately, monocularly.
When testing young children monocularly, use the first and second symbol of each line or every second line for one eye and the two last symbols of each or each other line for the other eye to determine on which line to start testing for threshold. This way the child cannot memorize the chart. Define the threshold level the same way as during the measurement of the binocular visual acuity.
Always remember to record the chart and the testing distance you used. This makes the follow-up more reliable, even if the child moves to another school and will be tested by another school nurse and another doctor.
If the chart is used at a distance other than the usual 3 meters (10 feet), measure and record the viewing distance and the symbol size (the M value) or the visual acuity value printed at the threshold line.
To determine the visual acuity use one of the following formulas:
Viewing Distance Used (meters)
Note that it is incorrect to report 'V.A. 20/25 at 5feet' if the child could read the 20/25-line (3.8M line) at 5 feet. When the distance is one half (or one third) of the standard distance, visual acuity value is also one half (one third) of the value printed next to that line, i.e. multiply the divider by 2(3).
An important detail in Visual Acuity testing:
If a child’s visual acuity has been measured until threshold with the distance test and the values are:
right eye 0.8 (20/25, 6/9); left eye 0.4 (20/50, 6/15)
it is not possible to know whether the left eye is amblyopic or myopic, except by measuring VA values at 40 cm (16 inches) distance with the LEA SYMBOLS® near test #250800.
Measurement of near vision acuity values already before the distance acuity testing give the information if the values were: binocular VA 1.0 (20/20, 6/6), right eye 0.8 (20/25, 6/9); left eye 1.0 (20/20, 6/6) at 40 cm (16 inches). The left eye must be myopic because VA value is normal at near and lower at distance. The child does not need to be referred for further examination by an ophthalmologist.
If vision screening uses pass/fail threshold 0.5 (20/40, 6/12) and both eyes have reached the 0.5 value, it does not guarantee that one of the eyes is not amblyopic. If the visual acuity of one of the eyes is 0.5 and that of the other eye 1.25 (20/16, 6/5), the eye with the 0.5 value is either amblyopic or there is another cause of lower than normal vision. The child needs to be referred.
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