Comparison of Globe Axial Length Measures in Children Using Contact Versus Immersion Ultrasound
Narrative Responses:
Purpose
To report differences in IOL calculation accuracy using immersion vs. contact ultrasound technique for pediatric cataract cases
Methods
Contact and immersion biometry measures were prospectively obtained by one observer using Sonomed E-Z scan (Sonomed Inc., Lake success, NY). One eye from bilateral patients was randomly selected for final analysis. Prediction error (PE) was calculated as: Predicted refraction - Actual refraction, within 4-6 weeks of surgery.
Results
Forty-eight eyes were analyzed (mean age at surgery, 6.3 +/- 5.7 years). Mean AL was 22.2 +/- 1.9 mm using contact and 22.1 +/- 1.9 mm using immersion. While this difference was not statistically different (p=0.8, unpaired t-test), 64% of the time, the reading obtained with contact was slightly longer than the immersion reading. The mean absolute PE was not significantly different, (1.0 + 0.6 diopters with both contact and immersion), but the median absolute PE was lower using immersion (1.01 D contact vs. 0.85 D immersion)
Conclusion
Careful placement of probe in children during contact ultrasound results in similar axial length measures and refractive outcomes to immersion ultrasound.