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Laura Anne Butler, Esther Misanjo, Duncan Middleton, Iain Livingstone, Petros Kayange; Evaluation of a Novel Digital Infant Acuity Test. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3196.
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© ARVO (1962-2015); The Authors (2016-present)
The testing of infant acuity is vital in treatment and prevention of amblyopia. Current card-based clinical standards encounter a number of problems including expense, wear and tear issues, portability and child engagement; digital devices provide the potential to resolve many of these limitations but have not yet been validated. The purpose of this study was to assess the validity of a novel digital tablet-based touchscreen high-frequency grating acuity test in Blantyre, Malawi.
Children aged 6 to 60 months who presented to the Eye Unit were eligible. Acuity was measured using “gold standard” Keeler cards and the Peekaboo digital test (see Figure 1) for right, left, and both eyes. Following a minimum interval of 20 minutes, patients were re-tested by the same assessor. In addition to age and LogMAR acuity, child engagement was recorded using a compliance score (CS) of 0-2 (0 = no engagement, 2 = perfect compliance). Statistical methods described by Bland and Altman were used to compare the two modalities.
A total of 58 patients were recruited with mean age of 33 months. The average difference in acuity between modalities was -0.1 (95% lower and upper LoA -0.69, +0.49 respectively). Subset analysis of children with CS of 2 for all tests (see Figure 2) revealed a difference of +0.02 (95 % LoA of -0.33 and +0.36 respectively). CS averaged 1.5 for the digital test, compared to 1.3 with Keeler (p<0.001). On test-retest analysis, the digital test showed an average difference of +0.007 (95% LoA -0.385 to 0.370) between first and second tests compared to Keeler which demonstrated a difference of -0.04 (95% LoA -0.683 to 0.674). The digital test demonstrated 95% repeatability coefficient of 0.29, compared with 0.38 for Keeler.
The present study demonstrates good levels of agreement between digital and card-based methods, with 95% LoA within appropriate limits for the young test population. The digital test outperformed Keeler in terms of child engagement and reliability. Digital high-frequency grating acuity testing represents a promising advance for assessing vision in the very young. Additionally, due to it's lower cost compared to current modalities, it has the potential for use in low to middle income countires, such as Malawi.
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