Pre-school vision screening by teachers in Enugu State, Nigeria: accuracy and willingness to conduct screening

Technical Summary: Pre-school Vision Screening by Teachers in Enugu State, Nigeria

Problem Statement
Visual impairment in preschool children (ages 3–5) can lead to irreversible developmental delays and learning deficits if not detected during the critical period before age 8. While vision screening is effective, its implementation in Nigeria and many African states is hindered by a shortage of qualified eye care professionals, high costs, and logistical challenges. Although trained teachers have been proposed as a cost-effective alternative for school-based screening, there is a lack of empirical data regarding the accuracy of teacher-conducted screenings for preschoolers in the Nigerian context, as well as limited understanding of teachers' willingness to undertake this additional responsibility.

Methodology
This descriptive cross-sectional study was conducted over one academic term (January–April 2022) in Enugu Metropolis, Nigeria. The study involved 750 pre-primary school pupils (aged 3–5 years) and 75 teachers selected through a multistage sampling approach across three Local Government Areas (Enugu East, North, and South).

• Training: Teachers underwent a two-day intensive training session covering visual acuity assessment using the HOTV chart, Hirschberg tests, and the identification of gross ocular anomalies. Proficiency was assessed, with teachers required to achieve ≥80% agreement with researchers on pilot cases.
• Procedure: Teachers screened pupils using the HOTV chart at a distance of 3 meters. Children were considered to have passed if they correctly identified 3 out of 5 letters on the 20/30 (6/9.5) line. Those who failed or were uncooperative were referred.
• Reference Standard: A research team comprising ophthalmology resident doctors and an ophthalmic nurse re-examined all pupils to serve as the reference standard.
• Data Analysis: Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated using the research team's findings as the gold standard. Teachers' willingness to conduct screenings was assessed via a Likert-scale questionnaire. Data were analyzed using IBM SPSS Version 20.0.

Key Results

• Demographics: Of the 750 recruited pupils, 746 (99.5%) completed screening by both teachers and the research team. The majority of participating teachers were female (86.7%), worked in private schools (68%), and held tertiary education (66.7%).
• Detection Accuracy:
  • Visual Impairment: The research team identified 16 pupils (2.1%) with visual impairment, while teachers identified 35 pupils (4.7%). This difference was statistically significant (p=0.01).
  • Sensitivity: Teachers demonstrated a sensitivity of 43.8% in detecting visual impairment, meaning they missed more than half of the cases identified by the doctors.
  • Specificity: Teachers showed high specificity at 96.2%.
  • Predictive Values: The Positive Predictive Value (PPV) was low at 20.0%, indicating a high rate of false positives (28 false positives vs. 7 true positives). The Negative Predictive Value (NPV) was high at 98.7%.
  • Gross Ocular Disorders: Teachers showed higher accuracy in detecting specific structural anomalies like squint (100% sensitivity) and red eye (100% sensitivity), though they over-detected nystagmus.
• Willingness: Despite the low sensitivity, 77.3% of teachers expressed high willingness to conduct vision screenings. The primary reasons for low willingness (reported by 8% of teachers) included the perception of extra workload and a lack of financial incentives.
• Correlates: No significant association was found between teachers' ability to correctly identify visual impairment and their age, gender, level of education, or years of teaching experience.

Significance and Claims
The paper concludes that while preschool teachers in Enugu State are highly willing to participate in vision screening programs, their sensitivity in detecting visual acuity abnormalities is low (43.8%). The authors note that this low sensitivity results in a high rate of false positives, which could lead to unnecessary referrals and strain on overburdened hospital systems.

The study highlights that the current two-day training period may be insufficient for teachers to master the screening process, particularly for the younger demographic (3–4 years) which presents unique challenges. The authors suggest that extending training duration and potentially implementing financial incentives could improve proficiency and participation. Ultimately, the study provides crucial evidence that while teacher-led screening is a viable and willing workforce strategy in Nigeria, it requires optimization in training protocols to ensure clinical accuracy before widespread adoption as a standalone screening protocol.