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

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• Standard Early Treatment of Diabetic Retinopathy Study (ETDRS) Sloan letters are widely used for research but are unsuitable for non-letter readers and show variable acuity.
• Existing pictogram sets often have fewer items, limiting their utility.
• There is a need for alternative optotype sets that provide consistent acuity estimates and are accessible.

Purpose of the Study:

• To develop an open-access set of 10 pictograms, The Auckland Optotype (TAO), designed for more consistent visual acuity measurement in visually normal adults.
• To compare the performance of TAO pictograms against ETDRS letters and Landolt Cs in terms of inter-optotype reliability and sensitivity.

Main Methods:

• Monocular visual acuity was measured for individual, uncrowded optotypes from the TAO set, ETDRS set, and Landolt Cs.
• Eleven visually normal adults were tested using regular and vanishing formats of each optotype set.
• Inter-optotype reliability and precision were assessed using intraclass correlations (ICC) and fractional rank precision (FRP).

Main Results:

• The TAO vanishing set demonstrated superior performance with the highest ICC (0.97) and FRP (0.90).
• Both regular and vanishing TAO formats outperformed ETDRS letters and Landolt Cs in reliability and precision.
• TAO optotypes showed greater equal legibility and sensitivity to individual differences compared to Sloan letters.

Conclusions:

• The Auckland Optotype (TAO) set offers a more reliable and sensitive method for measuring visual acuity in visually normal adults compared to existing standard optotypes.
• Its design, which does not require letter recognition, and its open-access nature make it broadly applicable for diverse populations and research settings.