A recent study looked at how accurate the reading charts are that eye doctors use to test your near vision. Researchers checked 19 different charts that are available internationally and used in community optometry clinics. They compared the charts to the detailed standards set by the International Organization for Standardization (ISO).
The main finding was that only one of the 19 charts (about 5%) had all its text sizes within the required tolerance. Most charts had text that was either too small or too large. Charts with serif fonts (like Times New Roman) tended to have text that was smaller than required, while charts with sans-serif fonts (like Arial) tended to have text that was larger.
All charts met standards for line spacing and contrast, but some were printed on glossy or laminated plastic instead of the required matte surface, which can cause glare. The study was small and only looked at the charts themselves, not at how these differences affect actual patient testing. This means eye doctors should be aware that switching between different charts might give slightly different results, especially when monitoring vision changes over time.