Iol Power Calculation In Long Eyes: Selection Of The Best Axial Length Adjustement Factor Using The Most Common Formulas

Comparing IOL power calculation formulas in long eyes (AL≥26.00 mm) to find the best axial length (AL) adjustment/IOL power calculation formula combination.

University Eye Unit, Department of Medicine, Surgery and Dentistry “Scuola Medica Salernitana”, University of Salerno, Italy.

In this retrospective study, patients that underwent standard phacoemulsification were recruited. Eyes were subdivided in 3 groups according to AL: 26.00≤AL<28.00mm, 28.00≤AL<30.00mm, AL≥30.00mm. Eight formulas that do not require anterior chamber depth (ACD) were evaluated with ULIB or IOLCon lens constants: Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO) 2.0, Ladas Super Formula (LSF), Hoffer Q, Holladay 1, SRKT, T2 and T2.2. Each formula was analyzed by using uncorrected AL (ALu) and following AL adjustments: Wang-Koch 1 (wk1), wk2, wk polynomial (wk-pol), estimated Cooke modified AL (CMALe) and ALc. Mean and median absolute errors, and percentage of eyes within ±0.50/±1.00 diopters (D) of prediction error were analyzed.

Five-hundred-fifty-four eyes of 554 patients with long eyes that underwent cataract surgery were examined. T2-ALu gave the best outcome when 26.00≤ AL<28.00mm. LSF-ALu, BUII-ALu, EVO 2.0-ALu, Holladay 1-wk-pol and T2.2-CMALe represented valid alternatives. EVO 2.0-ALc gave best outcomes when 28.00≤ AL<30.00 mm. Other thick-lens or hybrid artificial intelligence-vergence based formulas (BUII-ALu, LSF-CMALe) and Holladay 1-wk2 demonstrated greater reliability compared to thin lens-based formulas. EVO 2.0-CMALe gave best outcomes when AL≥30.00mm. Holladay 1-wk-pol e T2.2-wk1 represented valid alternatives (all p < 0.050). LSF could fail in 50 % of cases without ACD when AL≥30.00 mm.

Choosing the best AL adjustment/IOL power calculation formula combination for each AL subrange, can improve refractive outcomes in patients with long eyes that undergo cataract surgery.