Logarithmic Reading Charts Show Promise as Alternative to Traditional Letter Testing

Medical Check-up
Medical check-up run by IPL (Lille Institut Pasteur) in Arras, France. IPL delocalise these check-ups to help fragile sectors of the community who cannot travel to the Institute itself. A nurse tests the patient’s eye sight (ophtalmologic test for an illiterate patient). (Photo by: BSIP/Universal Images Group via Getty Images)
Individuals with cognitive impairments may particularly benefit from the use of logarithmic reading charts.

Logarithmic charts with sentences and words can be used in lieu of traditional letter acuity testing, particularly when assessing reading acuity, according to research published in Optometry and Vision Science

Investigators conducted a study to assess the efficacy of 4 logarithmic charts (the Colenbrander English Continuous Text Near Vision Card, Radner Reading Chart, Minnesota Reading Acuity Chart, and Smith-Kettlewell Reading Chart) in determining reading measures and compare them with conventional methods of visual assessment. They also examined the effects of linguistic factors on reading chart performance. 

The team enrolled 82 volunteers with emmetropia (mean age 26.73±7.32 years, 59 men) to assess reading measures including reading acuity, reading speed, and critical print size in the 4 logarithmic charts. They compared these measures  with more conventional methods, such as uncrowded and crowded letter acuity, stereoacuity, accommodation, and cognitive measures of word knowledge and ability. 

The researchers confirmed that performance on the reading measures (reading acuity, reading speed, and critical print size) was equivalent across charts, and reading test performance correlated with the more traditional measures of vision. The most consistent significant associations involved correlations between reading acuity and acuity for single-letter optotypes. The team noted no significant relationships between reading chart performance and cognitive measures of word knowledge and ability.

“Measures of word knowledge were not significantly associated with reading test performance,” according to the researchers. “This strengthens the value of these types of reading charts for assessing primarily visual influences on reading, independent of cognitive factors such as word knowledge.” From a clinical point of view, the investigators assert that individuals with compromised cognition are likely to benefit from this finding.

The study is limited by a small sample size and the strict inclusion of individuals with emmetropia. 


Maeni YA, Paterson KB, Maltby J, McGowan VA, Hutchinson CV. Comparison of logarithmic reading charts for visual assessment in normally sighted participants. Optom Vis Sci. 2022;99(3):292-297. doi: 10.1097/OPX.0000000000001865.