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Retinoscopic (refractive) estimation of axial length in paediatric aphakia: a comparison with ultrasonic measurement
1Division of Pediatric Ophthalmology, King Khaled Eye Specialist Hospital, Riyadh, 11462, Saudi Arabia. arif.khan@mssm.edu
Insights
Estimating paediatric axial length from aphakic refraction alone is a reliable method when ultrasound biometry is unavailable. This technique shows no significant difference compared to ultrasound measurements in children.
Area of Science:
- Ophthalmology
- Paediatric Optometry
- Biometry
Background:
- Accurate axial length measurement is crucial for paediatric eye care.
- Ultrasound biometry is the standard for axial length measurement.
- Estimating axial length from refraction offers a potential alternative.
Purpose of the Study:
- To compare paediatric axial length values derived from aphakic refraction alone with those obtained via ultrasound measurement.
- To assess the accuracy and reliability of estimating axial length from refraction in paediatric aphakic eyes.
Main Methods:
- Retrospective review of paediatric aphakic patients (≤12 years) with available ultrasound axial length and retinoscopy data.
- Estimated axial length using aphakic refraction and an assumed keratometry value (44 D).
- Paired t-test analysis to compare ultrasonic and estimated axial length values.
Main Results:
- 149 eyes from 102 patients were analyzed.
- No significant difference was found between ultrasonic (mean 22.47 mm) and estimated (mean 22.41 mm) axial lengths (p=0.56).
- Differences between measurements were randomly distributed, with larger discrepancies in eyes with unusual refractions or keratometry.
Conclusions:
- Estimating axial length from aphakic refraction is a viable and accurate method for the average paediatric eye.
- This technique is particularly useful when standard biometry equipment is inaccessible.
- Accuracy may be reduced in eyes with atypical refractive errors or keratometry values.
Aim:
To compare paediatric axial length values estimated from the aphakic refraction alone with axial length values measured by ultrasound.
Methods:
Retrospective institutional medical record review of paediatric aphakic patients 12 years of age and younger with documented ultrasonic axial length and objective refraction (retinoscopy) within 3 months of each other. An estimate of axial length was made from the aphakic refraction alone (with an assumed average keratometry value of 44 dioptres) for all patients.
Results:
149 eyes of 102 paediatric aphakic patients were identified. The ultrasonic axial length values (mean 22.47 mm, SD 1.69, 95% confidence interval (CI) 0.27) and estimated axial length values (mean 22.41 mm, SD 1.53, 95% CI 0.25) had an average difference of 0.05 mm (SD 1.04, 95% CI 0.17) and were not significantly different (p = 0.56) by the two tailed paired t test. A histogram of the differences that did exist between the two values resembled a normal distribution. The nine eyes with the largest differences between the two values had either low hyperopic aphakic refractions or abnormal average keratometry values.
Conclusions:
There was no significant difference between the two groups of axial length values, and the distribution of differences that did exist seemed random. The greatest differences between the two values occurred in longer (less hyperopic) eyes and in eyes with abnormally steep or flat keratometry. Estimation of axial length from the aphakic refraction alone seems to be a useful technique in the average paediatric eye, especially if biometry is unavailable.