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Biometric confirmation of the Hirschberg ratio in strabismic children
Insights
The Hirschberg conversion ratio (HR) is consistent in children aged 6 months to 11 years, validating its use across pediatric age groups. This ratio, crucial for strabismus assessment, shows minimal age-related variation in pediatric eyes.
Area of Science:
- Ophthalmology
- Pediatric Optometry
- Strabismus Diagnosis
Background:
- The Hirschberg conversion ratio (HR) relates strabismic angle to corneal reflex decentration.
- HR is influenced by corneal curvature radius and anterior chamber depth.
- Previous HR values were established for adults.
Purpose of the Study:
- To determine if the adult-established Hirschberg conversion ratio (HR) is applicable to children.
- To assess HR validity in pediatric patients across various ages.
- To investigate the impact of ocular structural growth on HR.
Main Methods:
- Measured corneal curvature radius and anterior chamber depth in 262 eyes of 131 children (6 months–11 years) under anesthesia.
- Calculated HR using a geometric model based on biometric measurements.
- Analyzed HR consistency across the pediatric age range.
Main Results:
- The calculated HR remained constant across all pediatric ages studied.
- The mean HR was 19.9+/-1.9 prism diopters/mm.
- No significant correlation was found between biometric measurements and age, despite observed scatter.
Conclusions:
- The averaged Hirschberg conversion ratio (HR) is applicable to children irrespective of age.
- Intersubject variability in HR must be considered in clinical practice.
- This finding supports the use of a standardized HR for pediatric strabismus evaluation.
Purpose:
In the Hirschberg eye position test, the ratio of strabismic angle to decentration of the corneal reflex is dependent on two biometric parameters of the eye: the radius of the corneal curvature and the depth of the anterior chamber. This study was designed to confirm whether the Hirschberg conversion ratio (HR) previously determined for adults can be used for children of various ages despite structural growth of the eye.
Methods:
For 262 eyes of 131 children with strabismus (age range, 6 months to 11 years), the radius of the corneal curvature was measured with an auto-keratometer and the anterior chamber depth with an A-scan ultrasound unit under general anesthesia before the surgery. Using these measurements, the HR was computed on the basis of a geometric model.
Results:
The calculated HR was constant across the age range, and the mean+/-SD was 19.9+/-1.9 prism diopters/mm (95% confidence interval, 16.1-23.6 prism diopters/mm). The ratios for the two eyes in each subject showed good correlation (R = 0.854, P = 0.0001). Neither of the biometric measurements was significantly correlated with age, although considerable scatter of the measurements was observed.
Conclusions:
These results indicate that the averaged HR can be applied in children regardless of the patient's age, although intersubject variance of the ratio should be taken into account.