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Amblyopia screening effectiveness at 3-4 years old: a cohort study
Sandra Guimaraes1,2, Andreia Soares3,2, Cristina Freitas2
1Ophthalmology, Hospital-Escola da Universidade Fernando Pessoa, Gondomar, Porto, Portugal sandraguimaraes.eye@gmail.com.
Insights
Early amblyopia screening in 3-4 year olds is highly effective, preventing future cases. For every 48 children screened, one case of amblyopia is prevented, highlighting the importance of this intervention.
Area of Science:
- Ophthalmology
- Pediatric Medicine
- Public Health
Background:
- Amblyopia, or 'lazy eye,' is a leading cause of preventable vision impairment in children.
- Early detection and treatment are crucial for effective amblyopia management.
- Current screening practices and their effectiveness in preschool-aged children require further investigation.
Purpose of the Study:
- To evaluate the effectiveness of amblyopia screening in a preschool population aged 3-4 years.
- To determine key epidemiological metrics including prevalence, treatment success, and screening efficiency.
- To assess the impact of early detection on long-term visual outcomes.
Main Methods:
- A cohort of 2300 children aged 3-4 years underwent comprehensive ophthalmological examinations.
- Amblyopia was diagnosed, treated, and monitored within the study cohort.
- Key metrics such as prevalence, absolute risk reduction (ARR), number needed to screen (NNS), and relative risk reduction (RRR) were calculated.
Main Results:
- Amblyopia prevalence ranged from 3.1% to 4.2% based on diagnostic criteria.
- Screening at ages 3-4 yielded an estimated ARR of 2.09% and an RRR of 87%, preventing future adult amblyopia.
- The Number Needed to Screen (NNS) was 47.8, with a treatment effectiveness of 88% for new diagnoses.
Conclusions:
- Population-based amblyopia screening at ages 3-4 is a highly effective public health strategy.
- Screening at this age prevents future amblyopia, with one case averted for every 48 children screened.
- Integrating primary care referrals for high-risk preverbal children with 3-4 year old screening offers a rational approach to amblyopia control.
Objective:
To study the effectiveness of amblyopia screening at ages 3-4.
Methods And Analysis:
From a population with no previous screening, a cohort of 2300 children with 3-4 years old attending school (91% of children this age attend school in Portugal), were submitted to a complete ophthalmological evaluation. Amblyopia was diagnosed, treated and followed. Amblyopia prevalence, treatment effectiveness, absolute risk reduction (ARR), number needed to screen (NNS) and relative risk reduction (RRR) were estimated.
Results:
Past/present history of amblyopia was higher than 3.1%-4.2%, depending on amblyopia definition normatives. Screening at age 3-4, had estimated ARR=2.09% (95% CI 1.50% to 2.68%) with a reduced risk of amblyopia in adulthood of 87% (RRR). NNS was 47.8 (95% CI 37.3 to 66.7). Treatment effectiveness of new diagnosis was 88% (83% if we include children already followed). 91% of new amblyopia diagnoses were refractive (of which 100% surpassed amblyopia Multi-Ethnic Pediatric Eye Disease Study criteria after treatment), while most strabismic amblyopias were already treated or undertreatment. Only 30% of children with refractive amblyopia risk factors that were not followed by an ophthalmologist, ended up having amblyopia at age 3-4. Eye patch was needed equally in new-diagnosis versus treated-earlier refractive amblyopia.
Conclusions:
Screening amblyopia in a whole-population setting at age 3-4 is highly effective. For each 48 children screened at age 3-4, one amblyopia is estimated to be prevented in the future (NNS). Screening earlier may lead to overdiagnosis and overtreatments: Treating all new diagnosis before age 3-4 would have a maximal difference in ARR of 0.3%, with the possible burden of as much as 70% children being unnecessary treated before age 3-4.Involving primary care, with policies for timely referral of suspicious/high-risk preverbal children, plus whole screening at age 3-4 seems a rational/effective way of controlling amblyopia.
