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Boy or girl? - a new visual acuity test screening tool

2013; Wiley; Volume: 91; Issue: 6 Linguagem: Inglês

10.1111/aos.12161

1755-3768

Tomoya Handa, Ran Nakadate, Tomoko Hatayama, Tsukushi Yokota, Nobuyuki Shoji,

Visual perception and processing mechanisms

Editor, Making young children understand the content of visual acuity tests is not easy. For example, it can be difficult to get them to understand the visual acuity test targets on the Landolt Ring chart or Snellen chart. Eye charts for children that use simple symbols as visual targets have been reported, but the need to understand the visual target itself has not changed (Kastenbaum et al. 1977; Woodhouse et al. 1992; Hered et al. 1997; Vision in Preschoolers Study Group 2010). For example, with the use of a picture visual target, they need to understand what the picture visual target itself is (horse, car, etc.). Development of a visual acuity test for screening that young children can understand and respond to in a short time and with little difficulty is needed. We have developed and verified a new screening visual acuity test for children. The subjects are 308 eyes of 154 children (5, 6 years old) who underwent a trial in a preschool visual function examination in the city of Sagamihara (Kanagawa, Japan). Sagamihara conducts that an ophthalmological examination is recommended for children with visual acuity test results of <0.7 (decimal visual acuity). In a bright room, a visual target was shown on a 32-inch TV monitor (TH-L32ET5, Panasonic Corporation, Kadoma, Osaka, Japan) and controlled by a PC using software made by the authors. Subjects sat at a test distance of 5.0 m, and their eyes were measured one at a time. The set-up for this screening visual acuity test is shown in Fig. 1A. The visual target in this test is a hybrid image that is set to look like a boy with visual acuity of <0.7 (decimal visual acuity) and to look like a girl with visual acuity of ≥0.7 (decimal visual acuity). The visual target for this test is shown in Fig. 1B. The line thickness of the girl’s hair and ribbon is set at 2 mm for a visual angle of 0.0247° at a test distance of 5 m. The contrast of the lines for the hair and ribbon was set at 53% based on previous verification. Visual acuity test results with the Landolt C chart are also divided into two levels of ≥0.7 (decimal visual acuity), and <0.7 (decimal visual acuity), with the results of the present screening visual acuity test and the visual acuity test with a Landolt C chart (uncorrected visual acuity) then compared. This study followed the tenets of the Declaration of Helsinki, and all subjects provided informed consent. (A) Setting for the screening visual acuity test. The visual target in this screening visual acuity test is displayed on a TV monitor at test distance of 5.0 m. The examiner covers one eye of the child being tested with an occluder and measures the unilateral visual acuity of the right eye followed by the left eye in that order. (B) The visual target for the screening visual acuity test. This visual target is a hybrid image, which looks like a girl if the ‘ribbon’ and ‘hair’ are recognized and looks like a boy if the ‘ribbon’ and ‘hair’ are not recognized. The rate of agreement between the results with this screening visual acuity test and the visual acuity using a Landolt C chart was 72.1% (agreement in 222 of 308 subject eyes) when evaluated based on the two levels of visual acuity, ≥0.7 (decimal visual acuity) and <0.7 (decimal visual acuity). All the children were able to understand the test with a simple explanation, and the test could be carried out over a short time period of about 10–20 seconds for each child. With the visual target in this screening visual acuity test, children could easily understand the test when they were simply asked, ‘Do you see a boy?’ or ‘Do you see a girl?’. In addition, with the use of a TV monitor to display the visual target, children naturally gaze at even a distant visual target. Based on these two advantages, it is thought that this screening visual acuity test for children could be carried out over a short period of time without difficulty, so that this test may be widely applicable for use in the visual acuity tests of children.