Cardiff Contrast TestThe Cardiff Contrast Test is designed for contrast sensitivity measurement in toddlers and young children, and in older children or adults with intellectual impairment or communication difficulties.
Contrast sensitivity is the ability of the visual system to detect large but faint targets. There are some pathological conditions that reduce contrast sensitivity without impairing visual acuity, and the test will help in the identification of these conditions. However, reduced contrast sensitivity and reduced visual acuity often occur together, so that some (by no means all) people with visual impairment also have reduced contrast sensitivity. Tests for the two functions are therefore complementary and obtaining a measure of both will give a fuller description of visual deficits than will one alone. Treatment for visual deficits (including amblyopia therapies) can result in improved contrast sensitivity sometimes in the absence of increased visual acuity. Contrast sensitivity can therefore be an essential tool in monitoring therapies. Contrast sensitivity is most usefully measured with a size of target well within a patient’s acuity limit. If acuity is good, then the peak of the contrast sensitivity function lies at around 1.5 - 4 cycles per degree. When the Cardiff Contrast Test is carried out at a distance of 50 cm the targets represent 1.9 cycles per degree (or 6/90, 20/300) and at a distance of 1 m the targets represent 3.8 cycles per degree (or 6/45, 20/150). At a distance of 25 cm the targets represent 1.0 cycle per degree (or 6/180, 20/600). For older children and adults, the test can be used as a naming test - at each level the patient is simply asked to name the picture. The test incorporates pictures suitable for both children and adults. Only one of each set needs to be shown. |
|
