When to Screen? 2.4.1
For many years, there has been a general belief among ophthalmologists that early detection of amblyopia gives better treatment outcome. Recent studies have shown contradictory results.
Williams et al.  compared an extensive program with orthoptist examinations on six occasions from age 8 months to age 37 months, with one orthoptist examination at age 37 months. Results showed that children subjected to the intensive screening protocol had a lower prevalence of amblyopia at age 7.5 years. Interestingly, more than half of amblyopic subjects in the intensive groups were found at 37 months, despite five previous examinations. A major drawback of the study is the large number of dropouts at the final examination; only slightly more than half attended at age 7.5 years, which makes the representativeness of the results questionable.
In two studies by the US-based Pediatric Eye Disease Investigator Group on moderate ambly-opia (VA 0.2-0.5) in children aged 3-7 years, no association was found between age and treatment effect [38,39]. In a study on severe amblyopia (VA 0.05-0.2) by the same group , no significant age effect was found when compar ing all age groups, but when pooling data and comparing younger children (<5 years old) to older children (5 to <7years old), a significant age effect was found with a larger improvement in younger children.
In a study of children aged 3-5 years, Clarke et al.  found no negative effect when treatment was delayed until age 5 years. Surprisingly, their data even showed that deferring treatment nearly halved the proportion of children needing patching treatment at all.
Results from the Monitored Occlusion Treatment of Amblyopia Study (MOTAS)  found a significant difference in improvement of visual acuity following occlusion with greater improvement for age less than 4 years, compared to age 4-6 years and over 6 years.
All in all, the results indicate a possible small age effect with better outcome for children younger than 4-5 years of age.
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