The Auckland Optotypes: An open-access pictogram set for measuring recognition acuity

Abstract

When measuring recognition acuity in a research setting, the most widely used symbols are the Early Treatment of Diabetic Retinopathy Study (ETDRS) set of 10 Sloan letters. However, the symbols are not appropriate for patients unfamiliar with letters, and acuity for individual letters is variable. Alternative pictogram sets are available, but are generally comprised of fewer items. We set out to develop an open-access set of 10 pictograms that would elicit more consistent estimates of acuity across items than the ETDRS letters from visually normal adults. We measured monocular acuity for individual uncrowded optotypes within a newly designed set (The Auckland Optotype [TAO]), the ETDRS set, and Landolt Cs. Eleven visually normal adults were assessed on regular and vanishing formats of each set. Inter-optotype reliability and ability to detect subtle differences between participants were assessed using intraclass correlations (ICC) and fractional rank precision (FRP). The TAO vanishing set showed the strongest performance (ICC = 0.97, FRP = 0.90), followed by the other vanishing sets (Sloan ICC = 0.88, FRP = 0.74; Landolt ICC = 0.86, FRP = 0.80). Within the regular format, TAO again outperformed the existing sets (TAO ICC = 0.77, FRP = 0.75; Sloan ICC = 0.65, FRP = 0.64; Landolt ICC = 0.48, FRP = 0.63). For adults with normal visual acuity, the new optotypes (in both regular and vanishing formats) are more equally legible and sensitive to subtle individual differences than their Sloan counterparts. As this set does not require observers to be able to name Roman letters, and is freely available to use and modify, it may have wide application for measurement of acuity.

Evaluation of vision screening of 5–15‐year‐old children in three Tongan schools: comparison of The Auckland Optotypes and Lea symbols

“…To address aim two, the agreement between the Lea chart and a new electronic acuity test was measured. The new test presented TAO on a tablet computer with automated test progression, termination and scoring . The outcome measure was 95% limits of agreement (LoA) between tests from Bland–Altman plots .…”

“…The electronic comparison test displayed TAO an open‐access picture optotype set. TAO symbols were designed to be balanced in the sense that each item elicits a similar visual acuity threshold to the other items .…”

“…The electronic comparison test displayed TAO an open‐access picture optotype set. TAO symbols were designed to be balanced in the sense that each item elicits a similar visual acuity threshold to the other items . They have been shown to produce accurate measures of recognition acuity in children in a parallel study in New Zealand .…”

“…Newer technologies offer several advantages over traditional methods. First, many electronic tests can be run on the user's own equipment (for example the Jaeb Visual Acuity Screener can be run on any Microsoft Windows device), and can present targets (‘optotypes’) which are open‐access (freely available, for example the standard Sloan letters or The Auckland Optotypes [TAO]). Second, automation of the testing procedure can reduce scoring and recording errors, streamline data storage, promote referral and facilitate follow‐up.…”

Binocular contrast summation and inhibition depends on spatial frequency, eccentricity and binocular disparity

“…Contrast sensitivity was measured using a modified quickCSF algorithm that controlled the spatial frequency and contrast of 26 band‐pass filtered Sloan font letters. We elected to use the full alphabet instead of a subset of letters because reducing the guessing rate greatly improves the efficiency of testing, this avoids forcing the subject to repeat a response when a target that is not in the subset is reported, and because identification differences are not avoided with subsets (see Hamm et al . for recent review).…”