Abstract
Purpose :
Reading and education are a well-recognised risk factors for myopia development, furthermore there are marked geographical differences in myopia prevalence in school age children. This study analyses the spatial frequency (SF) attributes of the printed text in a range of different alphabets/languages to determine the potential implications for myopia development.
Methods :
Texts in 12pt font in English (Roman alphabet), Russian (Cyrillic script), Greek, Hebrew, Arabic, Chinese (simplified and traditional characters), Korean and Japanese were analysed at a 30cm viewing distance. The page layout was identical for each language. A photopic luminance image was generated and analysed to generate rotationally averaged SF spectra. The slope of the log amplitude vs log SF relationship (SF slope) was the calculated for each text sample at low (0.5-2 c/deg), intermediate (2-8 c/deg) and high (8-32 c/deg) spatial frequencies.
Results :
Printed text has SF properties that differ markedly from natural or man-made images, yet the very different alphabets shared similar spatial characteristics. The log amplitude vs log SF relationship was highly non-linear with three distinct quasi-linear segments in low, intermediate and high SF ranges. This was most marked in Chinese text. There were also narrow spectral peaks corresponding to line spacing and/or character spacing. The slope of the low and intermediate SF segment was much flatter than natural images (low: mean -0.39, sd 0.30; intermediate: mean -0.27, sd 0.19) but the high frequency segment was much steeper, comparable to those reported for indoor environments (mean -1.76, sd 0.16) (See Table 1). There was a significant difference between low/intermediate and high SF slopes (P < 0.0001). All Asian languages showed a significantly steeper high SF slope than European/Middle Eastern languages (P < 0.0005). No significant differences were observed between serif and sans-serif fonts in English text.
Conclusions :
The printed word has very different spatial properties to natural scenes with increased contrast at low/intermediate SF, but reduced high SF content which resembles man-made environments. At high spatial frequencies Asian languages show a significantly steeper log amplitude vs log SF relationship than European/Middle Eastern languages. Spatial properties of the written word may potentially contribute to regional variations in myopia.
This is a 2021 ARVO Annual Meeting abstract.