Predictive Accuracy of Intraocular Lens Power Calculation by Immersion A- Scan Biometry and Contact A- Scan Biometry: A Comparative Study

Background: A-scan ultrasound biometry (A-scan biometry/ A-scan)is mainly used to determine the axial length of the eye with the help of an ultrasound device. Axial length of eye is an important parameter to calculate Intra-ocular lens (IOL) power prior to cataract surgery. Different formulae to calculate the IOL power need axial length value along with keratometry value (calculated using a keratometer). Sometimes, the corneal compression caused during the A-scan measurement gives wrong values of the axial length. The objective of the present study was to compare accuracy of intraocular lens power calculation by immersion A-scan biometry and contact A-scan biometry in a tertiary care centre. Material and Methods: The present hospital based comparative observational study was conducted at Department of Ophthalmology from July 2024 to September 2024.A total of 100 consecutive patients who underwent phacoemulsification and IOL implantation were included in the study. Informed written consent was taken from the participants of the study. Patients were divided into Group A as immersion group and Group B as Contact A-scan group with 50 patients each. Data entry and data analysis was done using MS Excel and epi info version 7. Results: Most of the patients were females in Group A (70%) and Group B (62%) with no statistically significant difference (P>0.05). The mean axial length in group A and Group B was23.07 and 22.65with statistically significant difference (P<0.05). The mean IOL power in group A and Group B was20.37 and 21.21respectively with statistically significant difference (P<0.05). Conclusion: The present study concludes that the immersion technique had better repeatability compared to Contact A-scan for intraocular lens power calculation.