Creation of Three New Optotypes Chart and Evaluation of the Reliability on Healthy Subjects

To design a new optotype that is not based on any Roman character.

Fifty healthy adults (12 men and 38 women), aged between 20-35 years, were enrolled. Three new optototypes were designed. The first is an open square, the second is a horned square, and the last is a horned circle. The main outcome is the correlation between Landolt C visual acuity and that measured using the 3 newly designed optotypes.

Mean subject age was 27.2 ± 3.7 years. Corrected visual acuity scores were similar across all five tests. Under fogging, the three new optotypes yielded significantly lower scores than Tumbling E and no significant difference was found between the Landolt C and the new optotypes. Bland-Altman analysis showed minimal bias and the closest agreement with Landolt C for the open square optotype, especially under fogging conditions (Bias: -0.006; 95% LoA: -0.172 to 0.160). All five tests were significantly correlated (P < 0.001), with the open square showing the strongest correlation with Landolt C. Among subjects, 33% had ≥1 diopter of with-the-rule astigmatism, but fogging did not reveal differences between astigmats and non-astigmats. Visual acuity was higher in non-astigmats for all optotypes except the open square.

Three newly developed and conventional optotypes including the Landolt C and Tumbling E tests to be similarly effective in measuring visual acuity. These optotypes can be considered as combinations of the Landolt C test.