Table 1

Types of acuity measures used in children with disability

Type of measurePrinciple of test and materialsAdministration/responseExamples
Resolution: of spatial detail, for example, black and white lines‘Vanishing target’—target that is not resolved ‘blurs’ to background
Child prefers to look at target that contains visual contrast
Child fixates target
Tester blind to location of target and makes judgement of child's fixation
Naming or pointing are not required
Keeler cards
Teller cards
Cardiff cards
RecognitionSome cognitive skill required—for example, matchingChild names or matches
Matching usually achieved through pointing
Lea symbols
Kay pictures
Sonksen LogMAR test