Axial length measurement using optical versus immersion ultrasound: Impact on predicted refractive outcome following cataract surgery

ABSTRACT

Objective: To evaluate optical vs immersion ultrasound biometry to measure ocular axial length (the distance between the anterior surface of the cornea and the fovea). Design and Methodology: The axial length of the eye is usually measured by A-scan ultrasonography or optical coherence biometry. Optical biometry is the gold standard, but cannot be used for patients with dense cataracts, when immersion ultrasound biometry is utilized. Both optical and immersion ultrasound biometry were performed on patients scheduled to undergo cataract surgery between November 2017 and November 2018. Statistical difference was determined using a two tailed t-test. Results: There was no statistical difference between mean axial length measured using optical biometry (23.83 mm ± 1.34) vs immersion ultrasound biometry (23.80 mm ± 1.30); t(46)= -0.05, p=0.96. Conclusion: Accurate axial length measurement is essential for reliable intraocular lens power calculation, minimizing refractive error following cataract surgery. The cost of optical coherence biometry equipment is prohibitive and this technology is not readily available in the public hospital eye clinics. There was no statistical difference in axial length measured using optical biometry and immersion ultrasound. This suggests that in low resource settings, immersion biometry can be utilized without compromising surgical outcome.