Greater effect of contrast polarities on visual acuity measurements using chart with shorter wavelength background


  • Chen Ai Hong Universiti Teknologi MARA
  • Nurulain Muhamad Universiti Teknologi MARA



Contrast polarity, Contrast ratio, Colour, Visual acuity


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.

Author Biographies

Chen Ai Hong, Universiti Teknologi MARA

Optometry and Vision Science Research Center (iROViS), Faculty of Health Sciences

Nurulain Muhamad, Universiti Teknologi MARA

Optometry and Vision Science Research Center (iROViS), Faculty of Health Sciences


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