The Influence of Uncontrolled Variables in Paediatric Assessment of Visual Acuity: Do we only Measure Visual Acuity?

Rebekah Duyshart BOrth

This paper aims to acknowledge the influence of test design features on visual acuity measurements in normal preschool children and to recognise this as an uncontrolled variable in research. Visual acuity and test duration time were measured and evaluated for three different visual acuity test types; Cambridge Singles, Cambridge Crowding Cards and the logMAR chart. Each test type has varying design features including the number of optotypes presented. The results indicate that the mean acuity decreased with the increased number of optotypes displayed. The design specifications and testing procedure were considered to be influential in these results as the age of the subject and test type influenced test duration time. This may imply that the acuity means are not solely reflective of the integrity of the visual system but the psychological processes used for each test type and these vary with age. However, test design and examination procedure become only uncontrolled variables when not acknowledged in comparisons made between tests in children of the same age or between age groups using the same test type.