Final answer:
Visual acuity assessments are most effective around ages 3-4 when children's cognitive and communicative abilities are sufficient for reliable testing with tools like the Snellen chart.
Step-by-step explanation:
The assessment of visual acuity in children is most effectively conducted around the age of 3-4 years. This is when children are better able to understand and follow instructions, which is essential for accurate testing using tools such as the Snellen chart.
Around the age of five, children's vision and cognitive abilities have typically matured enough to produce reliable visual acuity measurements. They have a well-developed vocabulary and cognitive abilities to respond effectively to the visual tests that determine their ability to see clearly at various distances.