The influence of contrast polarity during reading

Abstract

Purpose. The aim of this study was to investigate whether subfoveal choroidal thickness (SFCT) changes after 30 minutes of reading at a distance of 40 cm. In addition, it was investigated whether normal contrast polarity (black text on a white background) and inverted contrast polarity (white text on a black background) during reading have different effects on SFCT. Material and Methods. In this prospective crossover study, 36 young adults aged 18 to 30 years participated. To control for possible order effects, participants were divided into two groups. Group A first read a text with black letters on a white background and subsequently the same text with white letters on a black background, while in Group B the order was reversed. Each condition lasted 30 minutes at a distance of 40 cm. SFCT was measured using optical coherence tomography (Spectralis OCT, Heidelberg Engineering, Heidelberg, Germany) in enhanced depth imaging mode. Measurements were taken at baseline and after completion of each reading condition. Normality was assessed using the Shapiro–Wilk test. Depending on data distribution, paired t-tests or non-parametric tests were applied. In addition, a repeated-measures ANOVA was performed. Results. Statistical analysis showed no significant changes in SFCT after 30 minutes of reading within either contrast polarity condition. Furthermore, no significant difference was found between contrast polarities regarding the change in SFCT. Conclusion. In this study, contrast polarity during reading had no significant effect on SFCT in young adults.