EyeWorld India March 2021 Issue

Supplement to EyeWorld Asia-Pacific March 2021 Optimizing Refractive Outcomes: Using an Improved TK Formula for Cataract Surgery Copyright 2020 APACRS. All rights reserved. The views expressed here do not necessarily reflect those of the editor, editorial board, or publisher, and in no way imply endorsement by EyeWorld, Asia-Pacific or APACRS. may benefit from using the IOL power calculator on the ASCRS website (https://iolcalc.ascrs.org/) which allows one to select prior myopic LASIK/PRK, prior hyperopic LASIK/ PRK, or prior PRK. Alternatively, the IOLMaster 700 also has solutions for all these calculations onboard. Results of IOL power calculations after refractive surgery using Total Keratometry In one study, Lawless et al. (2020) analyzed prediction errors among dif- ferent IOL power formulas in 72 eyes of 50 patients in which prior refraction history was only known for 37 eyes. Formulas that were compared includ- ed the ASCRS mean, Barrett True K no history, Haigis-L, and Shammas IOL formulas. Additionally, the Barrett True K using posterior values (True K TK), Haigis-L, Haigis with TK, and Holladay 6 Double-K methods us- ing TK were also analyzed. Results showed a statistically significantly higher percentage of eyes within range of the refractive prediction “ The IOLMaster 700 is really opening up a new dimension with new measurements to improve our outcomes. Measuring the posterior corneal radius enables us to more accurately predict IOL power for post-refractive surgery patients. ” Dr. Yeo Tun Kuan, Singapore patient. Finally, third and most fourth generation biometry formulas esti- mate the ELP based on K readings, resulting in either an underestimate or overestimate of IOL power due to the flatness or steepness of the cornea after either myopic or hyperopic abla- tion. Surgeons who find it difficult to choose a proper calculation method First, patients may experience variation in their anterior corneal surface. After LVC, there will always be significant variation in the cen- tral corneal power compared to a virgin cornea. Second, as mentioned before, the anterior to posterior corneal curvature ratio may be flatter or steeper depending on the type of Figure 2. Third and fourth generation biometry formulas estimate the ELP based on K readings, resulting in either an underestimate or overestimate of IOL power due to the flatness or steepness of the cornea after either myopic or hyperopic ablation.] Zeiss IOLMaster 700 Zeiss IOL and OVD Portfolio