The VRF-L and VRF-GL IOL power calculation methods after radial keratotomy.

BACKGROUND: To investigate the accuracy of the VRF-L and VRF-GL IOL power calculation methods in cataract surgery after radial keratotomy (RK). METHODS: The VRF-L and VRF-GL methods were collated with nine formulas: Barrett True K (No History), Haigis, Hoffer Q, Hoffer Q (Double-K), Holladay 1 (Double-K), Holladay 2 (Double-K), PEARL-DGS (RK), SRK/T (Double-K), and T2 (Double-K). With SS-OCT biometry (IOLMaster 700, Carl Zeiss Meditec), data of 78 eyes from 78 patients with previous RK was included. Optimised lens constants were sourced from the IOL Con website. Subjective refraction was obtained at 4 to 5 months postoperatively. The root mean square absolute error (RMSAE) and median absolute error (MedAE) were chosen as primary outcomes and the percentage of eyes with PEs within ±0.25 D, ±0.50 D, ±0.75 D, and ±1.00 D were analysed. RESULTS: Statistical significance (Bootstrap-t test, P < 0.05) was shown by VRF-GL, VRF-L, and Haigis formulas with the lowest RMSAE (0.813 D, 0.816 D and 0.824 D) and MedAE (0.511 D, 0.497 D and 0.533 D) values. The Barrett True K formula was less predictable (0.836 and 0.580, respectively). The VRF-L, VRF-GL, and Haigis achieved the highest percentage of eyes with a PE within ±0.50 D (52.56%, 50.00%, and 46.15%) and ±1.00 D (79.49%, 79.49%, and 80.77% respectively). CONCLUSION: The VRF-L and VRF-GL methods demonstrated higher accuracy and were comparable with existing methods in eyes after RK. The Haigis was an alternative option with a higher percentage of eyes with a PE within ±1.00 D (80.77%).

Accuracy of the VRF and VRF-G Intraocular Lens Power Calculation Formulas Using Swept-Source Optical Coherence Tomography Biometry.

Purpose: To collate the accuracy of two recently introduced intraocular lens (IOL) formulas (VRF and VRF-G) in cataract patients using a swept-source optical coherence tomography (SS-OCT) biometry (IOL Master 700, Carl Zeiss Meditec AG, Jena, Germany). Patients and Methods: Data records of 295 eyes from 295 patients were included in this scrutiny. The IOLMaster 700 SS-OCT biometer was used for biometric measurements. The VRF and VRF-G formulas were compared with seven 3rd and 4th generation thin and thick-lens formulas: Haigis, Hoffer Q, Holladay 1, Holladay 2, SRK/T, T2, and Barrett Universal II. With optimized lens constants, the mean prediction error (PE) and its standard deviation (SD), the median absolute error (MedAE), the mean absolute error (MAE), and the percentage of eyes with PEs within ±0.25 D, ±0.50 D, ±0.75 D, ±1.00 D, and <±2.00 D were analyzed. Results: Statistically significant differences were found between formulas in the whole group (Friedman test, P = 0.000). The VRF-G and Haigis formulas showed the lowest SD values (0.464 D and 0.466 D respectively). The VRF and Barrett Universal II formulas were less predictable (SD 0.471 D and SD 0.474 D respectively). The biggest proportion of eyes within ±0.50 D was found with VRF-G (76.27%), Haigis (75.59%), VRF (74.92%), and Barrett Universal II (74.92%) formulas. Conclusion: Based on data achieved from the SS-OCT biometry, the VRF-G and Haigis methods were the more precise predictors of postoperative refraction with the biggest proportion of eyes within ±0.50 D.

Accuracy of 24 IOL Power Calculation Methods.

PURPOSE: To scrutinize the accuracy of 24 intraocular lens (IOL) power calculation formulas in unoperated eyes. METHODS: In a series of consecutive patients undergoing phacoemulsification and implantation of the Tecnis 1 ZCB00 IOL (Johnson & Johnson Vision), the following formulas were evaluated: Barrett Universal II, Castrop, EVO 2.0, Haigis, Hoffer Q, Hoffer QST, Holladay 1, Holladay 2, Holladay 2 (AL Adjusted), K6 (Cooke), Kane, Karmona, LSF AI, Naeser 2, OKULIX, Olsen (OLCR), Olsen (standalone), Panacea, PEARL-DGS, RBF 3.0, SRK/T, T2, VRF, and VRF-G. The IOLMaster 700 (Carl Zeiss Meditec AG) was used for biometric measurements. With optimized lens constants, the mean prediction error (PE) and its standard deviation (SD), the median absolute error (MedAE), the mean absolute error (MAE), and the percentage of eyes with prediction erros within ±0.25, ±0.50, ±0.75, ±1.00, and ±2.00 D were analyzed. RESULTS: Three hundred eyes of 300 patients were enrolled. The heteroscedastic method revealed statistically significant differences (P < .05) among formulas. Newly developed methods such as the VRF-G (standard deviation [SD] ±0.387 D), Kane (SD ±0.395 D), Hoffer QST (SD ±0.404 D), and Barrett Universal II (SD ±0.405) were more accurate than older formulas (P < .05). These formulas also yielded the highest percentage of eyes with a PE within ±0.50 D (84.33%, 82.33%, 83.33%, and 81.33%, respectively). CONCLUSIONS: Newer formulas (Barrett Universal II, Hoffer QST, K6, Kane, Karmona, RBF 3.0, PEARL-DGS, and VRF-G) were the most accurate predictors of postoperative refractions. [J Refract Surg. 2023;39(4):249-256.].

Comparison of the Barrett Universal II, Kane and VRF-G formulas with existing intraocular lens calculation formulas in eyes with short axial lengths.

BACKGROUND: To compare the accuracy of recently developed modern intraocular lens (IOL) power formulas (Barrett Universal II, Kane and VRF-G) with existing IOL power formulas in eyes with an axial length (AL) ≤ 22 mm. METHODS: This analysis comprised 172 eyes of 172 patients operated on by one surgeon (LT) with one IQ SN60WF (Alcon Labs, Fort Worth, TX, USA) hydrophobic lens. Ten IOL formulas were evaluated: Barrett Universal II (BUII), Haigis, Hoffer Q, Holladay 1, Holladay 2, Kane, SRK/T, T2, VRF and VRF-G. The median absolute error (MedAE), mean absolute error (MAE), standard deviation (SD) and all descriptive statistics were evaluated. Percentages of eyes with a prediction error within ±0.25 D, ±0.50 D, ±0.75 D and ±1.00 D were calculated using standard optimised constants for the entire range of axial lengths. RESULTS: The VRF-G, Haigis and Kane produced the smallest MedAE among all formulas (0.242 D, 0.247 D and 0.263 D, respectively) and had the highest percentage of eyes with a PE within ±0.50 D (75.67%, 73.84% and 75.16%, respectively). The Barrett was less accurate (0.298 D and 68.02%, respectively). Statistically significant differences were found predominantly between the VRF-G (P < 0.05), Kane (P < 0.05) and Haigis (P < 0.05) and all other formulas. The percentage of eyes with a PE within ±0.50 D ranged from 66.28% to 75.67%. CONCLUSIONS: In eyes with AL ≤ 22.0 mm, the VRF-G, Haigis and Kane were the most accurate predictors of postoperative refraction, and the Barrett formula was less predictable.

Clinical Accuracy of 18 IOL Power Formulas in 241 Short Eyes.

PURPOSE: To analyze the accuracy of 18 intraocular lens (IOL) power calculation formulas in eyes with axial length (AL) ≤ 22 mm. METHODS: We analyzed 241 eyes of 241 patients. Eighteen formulas were evaluated: Barrett Universal II (BUII), EVO 2.0, Haigis, Hoffer Q, Holladay 1 and 2, Cooke K6, Kane, LadasSuperFormula AI, Naeser 2, Olsen, Panacea, Pearl-DGS, RBF 2.0, SRK/T, T2, VRF and VRF-G. Optical biometry was performed with an IOLMaster 700 (Carl Zeiss Meditec, Jena, Germany). With lens constants optimized for the whole range of AL, the mean prediction error (PE) and its standard deviation (SD), the median absolute error (MedAE), the mean absolute error (MAE) and the percentage of eyes with PEs within ±0.25 D, ±0.50 D and <±1.00 D were calculated. RESULTS: Post-hoc analysis of the absolute PE revealed statistically significant differences (P < .05) between some of the newer formulas (K6, Kane, Naeser 2, Olsen and VRF-G), which obtained the lowest MedAE (respectively, 0.308, 0.300, 0.277, 0.310 and 0.276 D) and the remaining ones. These formulas yielded also the highest percentage of eyes with a PE within ±0.50 D (70.54%, 72.20%, 71.37%, 70.95% and 73.03%, respectively), whereas Panacea and SRK/T yielded the lowest percentage (62.24%), with a stastically significant difference (P < .05) with respect to most formulas. CONCLUSION: In eyes with AL ≤22.0 mm, new formulas (K6, Kane, Naeser 2, Olsen and VRF-G) offer the most accurate predictions of postoperative refraction.

Development and Clinical Accuracy of a New Intraocular Lens Power Formula (VRF) Compared to Other Formulas.

PURPOSE: To develop and compare the accuracy and reproducibility of the VRF intraocular lens (IOL) power calculation formula with well-known methods. DESIGN: Development and validation study. METHODS: This analysis comprised 823 eyes of 823 patients at Kiev Clinical Ophthalmology Hospital Eye Microsurgery Center, Kiev, Ukraine, operated on by 1 surgeon with 3 different types of hydrophobic lenses: IQ SN60WF (494 eyes) and ReSTOR SN6AD1 (169 eyes) (Alcon Labs, Fort Worth, Texas, USA) and AMO Tecnis MF ZMB00 (160 eyes) (J&J Vision, Santa Ana, California, USA). The full data set was divided into 2 subsets, the first to develop the new formula and the second to evaluate their performance with other most commonly used modern methods of IOL power calculation (Haigis, Hoffer Q, Holladay 1, Holladay 2, SRK/T, and T2). The VRF algorithm is empirical; it uses 4 predictors for estimation of postoperative lens position, including axial length, corneal power (K), preoperative anterior chamber depth (corneal epithelium to lens), and horizontal corneal diameter. The results are also stratified into groups of short (≤22 mm), medium (>22 to <24.5 mm), medium-long (≥24.5 to <26 mm), and long (≥26 mm) axial length. RESULTS: The mean error, median absolute error, and mean absolute error were evaluated for all 7 methods with 1 IOL type. The VRF formula had the lowest median (0.305 diopter [D]) absolute error over the entire axial length range, and was comparable with the formulas for T2 (0.321 D) and Holladay 1 (0.326 D). CONCLUSION: The new formula was comparable with well-known methods and was better over the entire axial length range.