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Z. Liu, M. Wu, D. Deng, Y. Tsau, S. Ye, Y. Zhao; A New Approach for Assessing Visual Acuity: A Study of Children Acuity Test. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3815.
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Vision tests with acuity charts require the capability of the subjects to recognize the abstractive symbols or letter orientation and to communicate with the examiner. We have developed a new computerized acuity test "Autoacuity", which avoids both prerequisites and can be widely used not only for cognitively developed subjects but also for young children inferior to symbol recognition, orientation and language communication. Our purpose of this study was (1) to compare its performance with the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart, and (2) to evaluate its feasibility for young children.
The Autoacuity utilizes computer to generate testing objects of different visual angles. The objective image is randomly presented in various position on a display with high resolution. The luminance of the background and the testing object is identical so that the object gradually merges into the background as its visual angle gets smaller. The subject uses a pointing device to identify the objects. The subject’s inputs are recorded and analyzed automatically thus no assistance was needed. The acuity is determined by the smallest visual angle that the subject could identify. Testing distance is 4.2 m. Luminance of the display is 250cd m-2 providing a contrast of 100%. 70 children (7 to 12 years) were tested with both the ETDRS Chart and Autoacuity Test. 114 subjects (2 to 6 years) were tested with only the Autoacuity; a retest was carried out 30min later.
(1) Comparison of two methods: The limit of agreement between the Autoacuity Test and the ETDRS Chart was (-0.19, 0.24). The coefficient of repeatability (COR) for an acuity score was calculated to be 0.19 log units for the Autoacuity and 0.17 for the ETDRS. (2) Feasibility of the Autoacuity: 114 children aged from 2 to 6 years old, with brief instruction, were all testable with the Autoacuity. It took 168.2 ± 68.4 sec for the subjects to finish at the first time; for the retest, the subjects finished at a significant faster speed of 132.1 ± 60.4 sec (P<0.001). The COR was calculated to be 0.20 log units, and the paired-T test (P=0.26) showed prominent stability for the new method.
The results showed that the Autoacuity and the ETDRS chart can be used interchangeably for testing wide population, while the Autoacuity test can also be sufficient for young children, making it an effective method for screening of amblyopia in early childhood.
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