Greater effect of contrast polarities on visual acuity measurements using chart with shorter wavelength background
DOI:
https://doi.org/10.11113/mjfas.v14n4.1134Keywords:
Contrast polarity, Contrast ratio, Colour, Visual acuityAbstract
Our study aimed to explore the effect of positive and negative polarities on visual acuity measurements by utilizing black and white as a text against background with three distinct colours. Visual acuity was recorded as logarithm of minimum angle of resolution (LogMAR) using the detection of the gap in a four-position Landolt-C. The 2x3 (polarity x background color) two way repeated measures ANOVA showed a statistically significant interaction between polarity and colour background on visual resolution [F (2, 16) = 23.704, p < 0.001, η2 = 0.744]. Among the three primary background colour, shorter-wavelength (blue background) showed statistically significant findings between both positive and negative polarity [F (1, 9) = 39.875, p < 0.001, η2 = 0.818]. Visual acuity measurements improved with negative polarity but decreased with positive polarity with blue colour background. However, visual acuity was not statistically significantly different with the green (medium-wavelength) [F (1, 11) = 0.625, p = 0.446, η2 = 0.053] and the red (long-wavelength) backgrounds [F (1, 9) = 4.021, p = 0.856, η2 = 0.000]. In conclusion, black text against shorter-wavelength (blue) background apparently more difficult to be resolved by human eyes compared with white text. These findings suggest colour element might be an advantage for negative polarity colour combinations.
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