Context / objectives

Amblyopia is the most common visual impairment in children and an accurate assessment of visual acuity (VA) is essential for the diagnosis. While the high-contrast logMAR VA ETDRS is the gold standard for adults, there is less agreement for pre-literate children. A new image optotype acuity test (The Auckland Optotypes [TAO]) has shown a favorable comparison to letter acuity graphs but has not yet been evaluated in children with amblyopia. This study compared the VA obtained using OAT to the overcrowded logMAR letters in children aged 5 to 8 years with amblyopia.

Methods

Children with amblyopia (m= 54 [20.37% strabismic, 18.52% anisometropic, 61.11% mixed], mean age 78.30 ± 11.72 months) were recruited from pediatric ophthalmology / orthoptic clinics at Moorfields Eye Hospital NHS Foundation Trust, London, and Cambridge Community Services NHS Trust, Bedford. The best-corrected VA was measured in both the amblyopic eye (AE) and the neighboring eye (FE) using OAT and a crowded letter acuity chart. Bland-Altman analysis was used to measure 95% limits of agreement (LoA) for the captured VA measurements (AE, FE and interocular difference [IOD]).

Results

A good agreement between the measurement of OAT and the letter VA was observed (mean bias: AE –0.01, FE 0.01, IOD –0.02). For AE measurements, 95% of LoA were –0.25 to 0.24 logMAR, which is similar for FE (–0.24 to 0.25) and IOD (–0.30 to 0.27) measurements ).

Conclusion

OAT and letters caused a similar VA in children with amblyopia. The OAT could be a useful picture chart for the assessment of pediatric vision.