Dynamic Optotype Test May Not Be Suitable for Refractive Error Assessment

The dynamic optotype (DYOP) visual acuity (VA) test demonstrates wide levels of agreement with letter charts and performs worse for detecting uncorrected astigmatism, according to research published in the Journal of Optometry. These findings suggest that the DYOP may not be optimal for assessing refractive error, according to the report.

Investigators performed a 2-cohort assessment to examine the validity, inter- and intra-session repeatability, and subjective participant preference between letter and DYOP testing. Cohort 1 included 103 participants (mean age, 29.2 years; 82 women) recruited from a single center. Participants underwent right eye corrected VA testing with DYOP and letter charts using a computer monitor. A subset of participants (n=75) underwent retesting within 2 weeks and completed a 4-item questionnaire to report their preferred method of testing. Cohort 2 included optometry students (n=29; mean age, 25.0 years; 18 women) from the State University of New York (SUNY) College of Optometry. The participants underwent VA testing with tumbling E, Landolt C, DYOP, and letter charts at baseline. Astigmatism was induced using cylindrical trial lenses (+1.00, +2.00, or +3.00 diopter [D] cylinders) at 45°, 60°, 90°, or 180° during subsequent testing. 

The mean [SD] VA was -0.02 [0.10] logarithm of the minimum angle of resolution (logMAR) and -0.04 [0.14] logMAR at baseline for cohort 1 using DYOP and letter chart testing, respectively. During a follow-up visit, VA was -0.05 [0.10] logMAR for the DYOP and -0.04 [0.15] logMAR for the letter chart. The mean difference (MD) between sessions differed significantly for DYOP (MD, 0.03; P <.001) but not for letter chart testing (MD, 0.01; P =.22).

Participants reported more frustration during the DYOP test compared with the letter chart test (P =.003). Participants reported similar subjective scores for both tests for the remaining survey items including how understandable and tiring the test was, and how confident they felt while taking the tests.

In cohort 2, no significant differences in VA were observed at baseline between tumbling E, Landolt C, DYOP, and letter chart tests before inducing cylinder (F_[3,155], 2.43; P =.07). However, mean levels of VA as a function of added cylinder power for the 4 charts were statistically significant as determined by a 3-factor analysis of variance  (chart: F_[3,1507], 136.05; P <.001; cylinder power: F_[2,15057, 519.45; P <.001 cylinder axis: F_[3,1507], 56.00; P <.001), according to the report. In a post-hoc analysis, the results from DYOP tests differed from other chart results (P <.01), but results from Landolt C, tumbling E, and letter charts did not differ from each other (P >.05).

“[W]hile the DYOP and letter chart measurements were significantly correlated, wide limits of agreement and significantly different mean values were obtained,” the study authors note. “Based on these findings, the current DYOP cannot be recommended for subjective refractions.” 

Study limitations include the use of convenience sampling, potential volunteer bias, and a narrow range in best-corrected VA among study participants.