Effect of simulated refractive error on adult visual acuity for paediatric tests Nabin Paudel 1 , Robert J. Jacobs 1 , Rebecca Sloan 1 , Sarah Denny 1 , Kimberley Shea 1 , Benjamin Thompson 1,2 and Nicola Anstice 1 1 School of Optometry and Vision Science, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand, and 2 School of Optometry and Vision Science, University of Waterloo, Waterloo, Canada Citation information: Paudel N, Jacobs RJ, Sloan R, Denny S, Shea K, Thompson B & Anstice N. Effect of simulated refractive error on adult visual acuity for paediatric tests. Ophthalmic Physiol Opt 2017; 37: 521–530. https://doi.org/10.1111/opo.12387 Keywords: astigmatic defocus, Cardiff Acuity test, children’s vision, Early Treatment of Diabetic Retinopathy Study chart, Lea symbols, spherical defocus, visual acuity Correspondence: Robert J Jacobs E-mail address: r.jacobs@auckland.ac.nz. Received: 19 January 2017; Accepted: 3 April 2017 Abstract Purpose: Although vanishing optotype preferential-looking tasks are commonly used to measure visual acuity (VA), the relative sensitivity of these tests to refrac- tive error is not well understood. To address this issue, we determined the effect of spherical and astigmatic simulated refractive errors on adult VA measures obtained using vanishing optotypes, picture optotypes and Sloan letters. Methods: VA was determined uniocularly for adults under conditions of spherical (0.0–3.0 DS; n = 23) and astigmatic (0.0–3.0 DC at 90° and 180°; n = 20) defocus using the Cardiff Acuity Test (vanishing optotypes), crowded linear Lea Symbols (picture-optotype recognition task) and the Early Treatment of Diabetic Retinopathy Study (ETDRS) letter chart. Results: The Cardiff Acuity Test over-estimated VA compared with the Lea Sym- bols and ETDRS charts in both focused and defocused conditions. The mean dif- ference between the Cardiff Acuity Test and the ETDRS chart was 0.31 logMAR (95% limits of agreement (LOA) 0.10–0.52 logMAR) in focused conditions and 0.64 logMAR (95% LOA 0.25–1.05 logMAR) with 3D of spherical defocus. Defo- cus degraded VA on all charts, however there was a significant chart-by-defocus interaction whereby the Cardiff Acuity Test was more resistant to the effects of both spherical (P < 0.0001) and cylindrical (P < 0.001) optical defocus than the recognition acuity tasks at all defocus levels. Conclusion: Although the Cardiff Acuity Test provides an easy method for VA measurement in infants and toddlers, there is a considerable overestimation of VA compared with recognition acuity tasks particularly in the presence of defo- cus. A simple correction factor (of for example three lines overestimate) cannot be applied to Cardiff acuity measures as there is increasing over-estimation of VA with increasing defocus. Infants with significant refractive error may fall within normal visual acuity ranges for the Cardiff Acuity Test. Introduction The measurement of visual acuity (VA) is an integral com- ponent of clinical vision testing. However, in preschool children, comparison of VA measures is complicated by the use of age-appropriate charts, which use a range of stimuli and testing paradigms. Because cognition and attention in children vary as a function of age, charts used with young children typically involve the assessment of resolution acuity and tests of recognition acuity are reserved for older children, 1 which use different stimuli and testing paradigms. Accordingly, the longitudinal mea- surement of visual acuity (VA) in early childhood typically involves multiple testing methods. In this context, it is important to understand the relationship between clinical measures of resolution and recognition acuity under nor- mal focused viewing and in the presence of defocus caused by refractive error. © 2017 The Authors Ophthalmic & Physiological Optics © 2017 The College of Optometrists Ophthalmic & Physiological Optics 37 (2017) 521–530 521 Ophthalmic & Physiological Optics ISSN 0275-5408