Comparison of the accuracy of axial length measurement by contact A-scan ultrasonography and optical biometry in patients undergoing cataract surgery

ABSTRACT Background: Cataract is the leading cause of reversible blindness and visual impairment throughout the world in older adults. Placement of an intraocular lens (IOL) after surgery requires an accurate calculation of the lens power necessary for attaining the optical postoperative refraction. Measurement of axial length (AL) is considered a key determinant in calculating the IOL power to be implanted. Two methods commonly available for the measurement of AL are the A-scan ultrasonography and the optical biometry. Objective: To evaluate the postoperative refractive outcomes after cataract surgery using two different AL measurement techniques of contact A-scan ultrasonography and optical biometry. Materials and Methods: A prospective observational study was conducted for one and a half years from June 2023 to December 2024, in the Department of Ophthalmology of a Tertiary Care Hospital in Imphal on 138 patients of senile immature cataract who were admitted for small incision cataract surgery with posterior chamber intraocular lens. Result: There were 138 patients, 69 in each group. The male-to-female ratio in group A (optical group) was 0.568, and in group B (A-scan ultrasonography [USG]), it was 0.468. The mean age of group A was 65.63 years, while that of group B was 65.56 years. There was a significant association between the postoperative visual acuity and the method of AL measurement used. There was no significant difference between the AL measured by optical biometry and A-scan USG ( P = 0.960). There was also no significant difference in the mean IOL power implanted in the two groups following the two methods of biometry ( P = 0.549). However, there was a significant difference in the mean autorefraction values ( P < 0.001) and subjective refraction values ( P < 0.001) in the two groups. Conclusion: The study suggests that optical biometry provides superior postoperative refractive outcomes compared to A-scan ultrasound, despite the two techniques yielding similar AL measurements. The study highlights the importance of precise biometry in achieving optimal visual outcomes following cataract surgery.