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Interobserver reliability of the prism and alternate cover test in children with esotropia
Insights
The prism and alternate cover test (PACT) shows reliable agreement for measuring childhood esotropia. Differences of 6-12 prism diopters (PD) or more likely indicate real changes in eye alignment.
Area of Science:
- Ophthalmology
- Pediatric ophthalmology
- Strabismus research
Background:
- Childhood esotropia is a common condition requiring accurate measurement of eye deviation.
- The prism and alternate cover test (PACT) is frequently used to quantify esotropia.
- Understanding the reliability and limits of agreement for PACT is crucial for clinical decision-making.
Purpose of the Study:
- To establish the 95% limits of agreement for measurements and differences between two measurements using the PACT in children with esotropia.
- To assess the reliability of PACT at both distance and near fixation.
Main Methods:
- A test-retest reliability study was conducted involving 143 children (≤60 months) diagnosed with esotropia.
- Two masked examiners performed PACT on each child once or twice, generating 199 test-retest pairs for distance and 239 for near fixation.
- Data analysis focused on calculating 95% limits of agreement for different magnitudes of eye deviation.
Main Results:
- For esotropia greater than 20 prism diopters (PD), 95% limits of agreement were ±7.3 PD (distance) and ±8.3 PD (near) for a single measurement, and ±10.4 PD (distance) and ±11.7 PD (near) for the difference between two measurements.
- For esotropia between 10-20 PD, 95% limits of agreement were ±4.1 PD (distance) and ±3.3 PD (near) for a single measurement, and ±5.8 PD (distance) and ±4.7 PD (near) for the difference between two measurements.
Conclusions:
- In childhood esotropia, a difference of 12 PD or greater for deviations over 20 PD, and 6 PD or greater for deviations between 10-20 PD, likely signifies a genuine change in eye alignment.
- Smaller observed differences may represent true changes or could be attributed to inherent measurement variability of the PACT.
Objective:
To determine 95% limits of agreement on a measurement and on a difference between 2 measurements for the prism and alternate cover test (PACT) at distance and at near fixation.
Methods:
In a test-retest reliability study, 143 children aged 60 months or younger with esotropia were examined by 2 masked examiners on 1 or 2 occasions yielding 199 test-retest pairs for PACT at distance fixation and 239 test-retest pairs for PACT at near fixation.
Results:
For angles greater than 20 prism diopters (PD), the 95% limits of agreement on a measurement and on a difference between 2 measurements were +/-7.3 PD and +/-10.4 PD, respectively, for PACT at distance and +/-8.3 PD and +/-11.7 PD, respectively, for PACT at near. For angles of 10 to 20 PD, the 95% limits of agreement on a measurement and on a difference between 2 measurements were +/-4.1 PD and +/-5.8 PD, respectively, for PACT at distance and +/-3.3 PD and +/-4.7 PD, respectively, for PACT at near.
Conclusion:
In childhood esotropia, differences of 12 PD or more for angles greater than 20 PD and differences of 6 PD or more for angles between 10 PD and 20 PD are likely to indicate real change. Smaller differences could be real change but could also be due to measurement error.
