Applanation Ultrasound versus Optical Biometry in the measurement of Axial Length in a Normal Eye

Objectives Accurate measurement of the axial length (AL) of the eye is important to make sure that the patient is emmetropic postoperatively. Multiple studies conducted around the globe compare AL using optical and ultrasound biometry. However, results are still inconclusive, as some studies stated that there is no difference in both modalities, whereas other studies considered optical biometry to be more superior. We aim to compare AL measurements using applanation ultrasound and optical biometry AL Scan, in Islamabad, in order to find out which modality is more superior. Methods This was a prospective cross-sectional study that was conducted at the department of Ophthalmology, PAF Hospital, E9 Islamabad. The study was conducted over a period of eight months, from April to November 2023. Participants were enrolled using non-probability, consecutive sampling. The axial length of each eye was measured by both optical and ultrasound biometer. Results There were 80 eyes of 40 participants including both males (77.5%) and females (22.5%) aged between 16-58 years. The axial length using the optical biometer showed a greater value ranging from 22.01 to 30.18mm with a mean value of 23.89 ± 1.31mm whereas the axial length measured using applanation ultrasound was 21.62 to 30.00mm with a mean of 23.53 ± 1.29mm. The mean difference between both was 0.36 ± 0.21mm which was statistically significant (P <0.005). Conclusion There is a statistically significant difference between the mean readings of the AL measured by the IOL master and ultrasound biometer, so both the devices cannot be used interchangeably.