Success rates in testing monocular acuity and stereopsis in infants and young children.

This study demonstrated how success in stereopsis and monocular acuity testing in the under-fives changes with age. Monocular testing was least successful with 1-2-year olds, while success with stereopsis testing increased linearly to 100% by 3 years. The differing patterns mean that a reasonable degree of success with one test or the other is likely whatever a child's age. Since the demonstration of either stereopsis or normal monocular acuities rules out the presence of any gross visual anomaly, the age-appropriate use of the two types of testing will facilitate the early detection of any abnormality.