INTRAOCULAR LENS POWER CALCULATION ADAPTED TO SUTURELESS SCLERAL FIXATION WITH YAMANE TECHNIQUE.

Purpose: To assess reliability of different IOL power calculation formulas in secondary IOL implantation with sutureless scleral fixation (Yamane technique).

Setting: "San Maurizio" Hospital, Bolzano, Italy; University of Salerno, Italy.

Design: Retrospective cohort study.

Methods: Fifty eyes of 50 patients who underwent secondary IOL implantation with Yamane technique were analyzed. Surgery was performed with a standardized technique using the needle stabilizer. Barrett Universal-II, EVO-2.0, Hoffer-Q, Holladay-1, SRKT, T2 and T2.2 formulas were analyzed in terms of mean error (ME), median absolute error (MedAE) and percentages of eyes with refractive prediction error (PE) less than ±0.50/±1.00D. Both IOLCon and optimized constants through zeroing-out the MEs were analyzed. Additionally, formulas were also tested with decreased optimized-IOLCon constants (DOC) by a fixed value of -0.5.

Results: All formulas reported a myopic shift of MEs with IOLCon constants (ranging from -0.43D to -0.31D, all p<0.050). No statistically significant differences among methods in terms of MedAE were reported both with IOLCon and optimized constants (all p>0.050). By using DOC-0.5, all formulas reported MEs not different from zero (all p≥0.491) and all MEs were lower than IOLCon MEs (all p<0.001), with comparable MedAE and percentages of eyes with PE less than ±0.50/±1.00D (all p>0.050).

Conclusion: In case of "out-of-the-bag" IOL implantation, a systematic error independent from the applied formula but linked to surgery technique was found. Using DOC-0.5 can eliminate such a bias. The study highlights the importance of refining lens constants in case of scleral fixation, to eliminate any systematic error in IOL power calculation.