COMPARATIVE STUDY OF ACCURACY OF BIOMETRIC FORMULAS OBTAINED BY APPLANATION A-SCAN BIOMETRY

Aim of the study: To evaluate and compare the accuracy of different intra ocular lens (IOL) power calculation formulas for predicting post operative refraction in eyes of different axial lengths using applanation A scan biometry Methods: In prospective study, conducted in GREH, Visakhapatnam with 50 eyes.Axial lengths were calculated by applanation A-scan biometry. All eyes were divided into three groups according to AL: short (<22.0 mm), average (22.0?25.0 mm), and long (>25.0 mm) eyes. IOL power calculation was done using the five Formulas SRKII, SRK/T, HOLLADAY 1, HOFFERQ, and BINKHORST 2. All patients were subjected to SICS with PCIOL implantation under local anaesthetia.The implanted power of IOL was based on SRK II formula. Final refraction was measured 6 weeks postoperatively.Post-operative spherical equivalent (SE) was calculated and compared with predicted refractive error using each biometric formula. Results: All formulas had a significantly lower MAE in comparison with BINKHORST II formula. SRK II and SRK/T had lowest MAE (0.58?0.44) for all eyes. SRK II had the lowest MAE for average (0.54?0.40) and short (0.67?0.54)eyes.SRK/T had the lowest MAE (0.63?0.48) for long eyes. BINKHORST II formula had highest MAE for all (0.69?0.48) and average (0.68?0.46) eyes. HOFFER Q formula had highest MAE (0.76?0.65) for short eyes and SRK II had highest MAE (0.89?0.64) for long eyes Conclusion:SRK II and SRK/T are accurate formulas for average eyes.SRK II and HOLLADAY I are best formula of choice in short eyes.SRK/Tis accurate IOL formula for long eyes followed by HOLLADAY I and HOFFER Q .