Comparison of accuracy between ultrasound B scan and partial coherence interferometry (IOL master) in IOL (intraocular lens) power calculation

Aims and Objectives: To compare the accuracy of ultrasound A scan biometry and IOL master (PCI) biometry in intraocular power calculation, by doing a comparative study of difference in biometry by conventional methods and optical biometry (IOL master). Materials and Methods: Place of study: Aravind Eye Hospital, India. Design of Study: Prospective, non randomised, clinical study. Study Group and Duration: The study involves patients who underwent cataract surgeries at Aravind Eye Hospital, Tirunelveli during the specified time period. The IOL power and predicted refractive outcome were calculated for every patient by both the methods, A scan ultrasound Biometry IOL master (Partial Coherence interferometry) Inclusion Criteria: Only those patients in whom it was possible to secure a reliable IOL master reading (on the basis of good SNR), were included. Results: In a 12 month period, 337 eyes were consecutively enrolled in the study. Both ultrasound A scan and partial coherence interferometry was performed and IOL power implanted as per the IOL master. Inclusion criterion and exclusion criterion used as mentioned. The difference in between the final and predicted refraction is compared for both the groups. The overall Mean absolute error was 0.402 ± 0.407 with the ultrasound A scan & 0.388 ± 0.406 for the IOL master, with the probability value (p-value) 0.3802. The mean numerical error (the difference between the refractive outcome and the predicted spherical equivalent) is -0.226 ± 0.526 (min -2.66 & max 2.06) for the ultrasound scan group and -0.217 ± 0.518 (min -2.41 & max 2.10) for the IOL master group, with the probability value (p-value) being 0.514. We got a comparative result in our study, though not significant, but it is more in favour of IOL master (PCI) as per the mean absolute error and mean numerical error calculations. When analysing the Mean Axial Length readings, the findings were almost similar, with an insignificant p-value.