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Assessment of Visual Acuity in Children Using Crowded Lea Symbol Charts

Sailoganathan, Ananth, PhD1; Rou, Leong Xin, BScOptom1; Buja, Kenny Anak, BScOptom1; Siderov, John, MScOptom, PhD, FAAO2*

doi: 10.1097/OPX.0000000000001253
ORIGINAL INVESTIGATIONS

SIGNIFICANCE Vision charts comprising single Lea symbols surrounded by either flanking bars or flanking Lea symbols are available for measurement of visual acuity in children. However, the results obtained with such charts may not be interchangeable owing to potential differences in the crowding effect.

PURPOSE The purpose of this study was to compare habitual visual acuity in a sample of young children using two versions of the single Lea symbols charts with different crowding features.

METHODS Monocular habitual visual acuity was measured in a sample of 77 young children aged between 4 and 6 years using crowded Lea symbols charts with either flanking bars separated from the central symbol by 0.5 optotype width or flanking Lea optotypes separated from the central symbol by 1.0 optotype width.

RESULTS Mean visual acuity was higher (i.e., lower logarithm of the minimum angle of resolution) with the Lea symbols crowded using flanking optotypes, equivalent to about 1.5 optotype difference. Visual acuity measured with the two charts was significantly correlated; however, the 95% limits of agreement were larger than expected from repeatability studies using Lea symbols.

CONCLUSIONS Lea symbols with flanking optotypes resulted in higher visual acuity than the Lea symbols with flanking bars, probably as a result of differences in the crowding effect. The two charts showed insufficient agreement, and we do not recommend their use interchangeably. We recommend using the Lea symbols with flanking bars because of the closer flanker-target separation.

1National Institute of Ophthalmic Sciences, Tun Hussein Onn National Eye Hospital, Petaling Jaya, Selangor Darul Ehsan, Malaysia

2Anglia Vision Research, Department of Vision and Hearing Sciences, Anglia Ruskin University, Cambridge, United Kingdom *john.siderov@anglia.ac.uk

Submitted: October 6, 2017

Accepted: June 10, 2018

Funding/Support: None of the authors have reported funding/support.

Conflict of Interest Disclosure: None of the authors have reported a financial conflict of interest.

Author Contributions: Conceptualization: JS; Data Curation: AS, LXR, KAB; Formal Analysis: JS; Investigation: LXR, KAB; Methodology: AS, JS; Supervision: AS; Writing – Original Draft: AS, LXR, KAB, JS; Writing – Review & Editing: AS, JS.

© 2018 American Academy of Optometry