Comparative study of axial length measurement using B scan and A scan biometry in intra ocular lens power calculation
Journal Title: Medpulse International Journal of Ophthalmology - Year 2019, Vol 9, Issue 3
Abstract
Abstract Background: Intra Ocular Lens power calculation are done preoperatively using different formulas like SRK-1, SRK-2, SRK-T, Holladay, Hoffer- Q, Haigis. They need Eye’s Axial Length (L)2, Corneal power (K)5, Estimated Lens Position post operatively (ELP) and A- constant for accurate IOL power (P) calculation to get emmetropic vision after surgery. Axial length of the eye ball can be measured by many methods like A scan, B Scan, OCT etc. Aim: To compare the accuracy of B-mode guided biometry with that of Contact A Scan biometry in preoperative IOL Power calculation and to assess the reproducibility while measuring the axial length of eye ball. Materials And Methods: Axial length of 50 eyes(Group A) were calculated using A scan contact biometry. In the other 50 Preoperative eyes(Group B) , B Scan were used to calculate the Axial length of eyeball . IOL power calculation were done for both groups using SRK -2 formula. For all these patients, cataract surgery were perfomed by Phaco emulsification method in the period of Feb 2015 till Jan 2016. Postoperative refractive status were calculated and tabulated after 45th postoperative day and comparison were done between both the groups. Results: Postoperative refraction for all 100 patients calculated and the details tabulated. The deviation of +/- 0.75Dsph and more of postoperative refraction is noted and tabulated. The axial length measured by B scan(22.9+1.3) was slightly longer than that measured by A-Scan(22.8+1.2). Postoperative refractive error showed mean of -0.045 in A Scan and-0.015 in B Scan. Postoperative refractive error showed Standard deviation of 0.43 in A Scan and 0.214 in B scan. Both the data’s are compared with paired t test and chi square test. Emmetropia is significantly higher in patients for whom IOL was implanted with the Axial length measured by B Scan(x2 =23.52, p=0.001) than the A Scan. Conclusion: Axial length measurement done by B Scan measurement gives less variation in readings and also better postoperative refractive stability compared to Axial length measurement done by A Scan biometry.
Authors and Affiliations
Venkatesan C, Sundara Rajan
Keywords
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