Lens Factor Choice In Iol Power Calculation After Laser Refractive Surgery: The Right Constant For Advanced Lens Measurement Approach (Alma)
Published 2025 - 43rd Congress of the ESCRS
Reference: FP21.04 | Type: Free paper | DOI: 10.82333/s695-7a84
Authors: Mario Troisi* 1 , Marco Fantozzi 2 , Ciro Caruso 3 , Massimo Mammone 2 , Chiara Fantozzi 4 , Raffaele Piscopo 1 , Ciro Costagliola 1
1Ophthalmology Department,University of Naples Federico II,Naples,Italy, 2Ophthalmology Department,San Rossore Medical Center,Pisa,Italy, 3Ophthalmology Department,Pellegrini Hospital,Naples,Italy, 4Ophthalmology Department,Policlinico Gemelli Hospital,Rome,Italy
Purpose
To evaluate the advanced lens measurement approach (ALMA) formula accuracy using different lens constants available on the user group for laser interference biometry (ULIB) and IOLCon platforms.
Setting
University Eye Unit, Department of Medicine Surgery and Dentistry “Scuola Medica Salernitana”, University of Salerno, Italy.
Methods
In this retrospective study, patients with previous myopic Photorefractive Keratectomy or laser-assisted in situ keratomileusis, who underwent uneventful cataract surgery, were examined. The ALMA formula was used to calculate the refractive prediction error (PE), analyzing four different categories of lens constants: both nominal and optimized A-Constant for SRKT, which are available on the ULIB and IOLCon platforms. An additional analysis was carried out in this study, evaluating if a decreased ULIB optimized constant (DUOC) with different fixed factors (−1.2 −1.3 −1.4 −1.5) could improve refractive outcomes. Median absolute error (MedAE) and percentage of eyes within ±0.50 and ±1.00 diopters (D) of prediction error were evaluated.
Results
One-hundred-sixty eyes of 160 patients were evaluated. Comparing the lens factors available on ULIB and IOLCon platforms, the ALMA formula reported a lower MedAE and higher percentages of eyes with a refractive PE within 1.0D using ULIB nominal constants (all p < 0.05). Using DUOC (−1.3), a mean error not different from zero was reported (p >0.05), meaning that any systematic error was eliminated. In addition, there was a statistically significant improvement of both MedAE and percentages of eyes with PE within ±0.50 D with the ALMA method compared to nominal ULIB constants (all p < 0.05).
Conclusions
The impact of different lens factors in the IOL power calculation after myopic LRS should be carefully evaluated. The ALMA formula, in the absence of optimized constants by zeroing the mean error, should be used by subtracting 1.3 from the optimized ULIB constants available on the IOL Con website. This finding suggests further studies to test which of these constants could work better with the other post-refractive surgery formulas.