Assessment of visual acuity in relation to central nervous system activation in children with mental retardation

Assessment of visual acuity was combined with observations of behavioral state indicating CNS activation in 24 individuals with mental retardation. Visual acuity was assessed by presentations of Teller Acuity Cards on two occasions. Behavioral state was classified along a scale with four categories during visual acuity testing. Results showed good test-retest reliability for the Teller Acuity Cards. Six participants had different behavioral state scores on the two test occasions, but displayed similar visual acuity on both tests. No participant rated as "drowsy" displayed responses on the acuity test. Results indicate that forced-choice preferential-looking technique can be used to test visual acuity in this population unless the participant is drowsy.