Preliminary clinical validation of a new picture-based visual acuity test in children with amblyopia: a comparison of The Auckland Optotypes and crowded logMAR letters.

Abstract

Amblyopia is the most common visual deficit in children and accurate visual acuity (VA) assessment is essential for diagnosis. While ETDRS high-contrast logMAR VA is the reference standard test for adults, less agreement exists for pre-literate children. A new picture optotype acuity test (The Auckland Optotypes [TAO]) has shown favourable comparison to letter acuity charts but has not yet been evaluated in children with amblyopia. This study aimed to compare VA obtained using TAO to crowded logMAR letters in children age 5-8 years with amblyopia. Children with amblyopia (n = 54 [20.37% strabismic, 18.52% anisometropic, 61.11% mixed], mean age 78.30 ± 11.72 months) were recruited from paediatric ophthalmology/orthoptic clinics at Moorfields Eye Hospital NHS Foundation Trust, London, and Cambridge Community Services NHS Trust, Bedford. Best-corrected VA was measured in both the amblyopic eye (AE) and fellow eye (FE) using TAO and a crowded letter acuity chart. Bland-Altman analysis was used to measure 95% limits of agreement (LoA) for VA measures captured (AE, FE and interocular difference [IOD]). Good agreement between TAO and letter VA measurement was observed (mean bias: AE -0.01, FE 0.01, IOD -0.02). For AE measures 95% LoA were from -0.25 to 0.24 logMAR, this being similar for FE (-0.24 to 0.25) and IOD measures (-0.30 to 0.27). TAO and letters elicited similar VA in children with amblyopia. TAO could be a useful picture-based chart for paediatric vision assessment.