2021 ASCRS Annual Meeting

Authors

Presenting Author
Li Wang, MD, PhD    Email the author
Authors
Douglas D. Koch, MD, ABO

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Paper Abstract

Purpose
To compare the accuracy of residual astigmatism prediction using either theoretical adjustment of posterior corneal astigmatism or measured posterior corneal astigmatism.

Methods
A dataset of 1905 eyes was obtained from cases that had been planned with the VERACITY Surgical. The Barrett Toric calculator was used to recalculate the predicted postoperative residual astigmatism with: 1) IOLMaster 700 anterior corneal astigmatism combined with theoretical adjustment of posterior corneal astigmatism (standard Barrett toric calculator), and 2) IOLMaster 700 anterior corneal astigmatism combined with measured posterior corneal astigmatism (new Barrett toric calculator). Vector analysis will be performed. Astigmatism prediction error using the standard and new Barrett toric calculators will be calculated and compared.

Results
A dataset of 602 eyes was included. All eyes had monofocal non-toric IOLs. Compared to the standard Barrett, the new Barrett produced a significantly 1) smaller mean vector astigmatism PE magnitude (0.54 D vs 0.57 D), 2) higher percentage of eyes with vector PE of ≤0.5 D (57.6% vs 52.5%) (P<0.05), and 3) in eyes with anterior corneal astigmatism ≥0.5 D, higher percentage of eyes with vector PE of ≤0.5 D (50.5% vs 46.3%, P<0.05).

Conclusion
Compared to the standard Barrett toric calculator that uses anterior corneal measurement with theoretical estimation of posterior corneal astigmatism, the new Barrett toric calculator incorporating measured posterior corneal astigmatism was more accurate in predicting residual astigmatism in eyes implanted with nontoric IOLs.

Authors

Presenting Author
Kathryn M Durnford, BSc, COA    Email the author
Authors
Olga Reitblat, MD, MHA, Sina Khalili, MD, Asim Ali, MD, FRCSC, Kamiar Mireskandari, FRCOphth, PhD, Uri Elbaz, MD, Ruti Sella, MD

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Paper Abstract

Purpose
To assess the accuracy of the Kane formula for intraocular lens (IOL) power calculation in comparison to established formulas in the pediatric population.

Methods
The charts of all pediatric patients who underwent uneventful cataract extraction surgery along with in-the-bag IOL implantation between 2012-2018 were reviewed retrospectively. One of two IOL models (SA60AT or MA60AC, Alcon Laboratories, Fort Worth, TX) was implanted in the capsular bag of all eyes. The accuracy of the Kane formula was evaluated in comparison the Barrett Universal (BUII), SRK/T, Holladay I, Hoffer Q and Haigis formulas. Mean prediction error (PE) were calculated and zeroed by adjusting PE for each eye by an amount equal to the mean PE of that formula. The optimized mean and median absolute PE (APE) were calculated for the six different IOL formulas investigated.

Results
Sixty-two patients (39 with SA60AT and 23 with MA60AC) aged 83.2±55.2 months were included. Median and mean APE of the Kane formula (0.54 and 0.91±1.04 D) were comparable to the BUII (0.51 and 0.90±1.02 D, p=0.70), Haigis (0.51 and 0.98±1.12 D, p=0.77), Hoffer Q (0.52 and 0.89±1.04 D, p=0.16) and Holladay I (0.58 and 0.94±1.04 D, p=0.29). In addition, the Kane formula produced similar predictability within 0.5D (47%) compared with BUII (48%, p=1.00), Haigis (48%, p=1.00) and Hoffer Q (45%, p=1.00). A non-significant superiority of Kane compared with the SRK/T formula was observed (APE: 0.71 and 0.98±0.99 D, respectively, p=0.09, and predictability within 0.5D: 32%, p=0.06).

Conclusion
This is the first study to show the results of the Kane formula after constant optimization in the pediatric age group. The Kane formula had comparable accuracy to other tested formulas, with a tendency to outperform the SRK/T formula, when calculating IOL power in pediatric eyes undergoing cataract surgery.

Authors

Presenting Author
Kathryn M Durnford, BSc, COA    Email the author
Authors
Olga Reitblat, MD, MHA, Uri Elbaz, MD, Sina Khalili, MD, Ruti Sella, MD, Yakov Vega, MD, Asaf Achiron, MD, Asim Ali, MD, FRCSC, Kamiar Mireskandari, FRCOphth, PhD

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Paper Abstract

Purpose
To compare the accuracy of the Barrett Universal II (BUII) formula to previous generation formulae in calculating intraocular lens (IOL) power following pediatric cataract extraction.

Methods
The charts of all pediatric patients who underwent uneventful cataract extraction surgery along with in-the-bag IOL implantation between 2012-2018 were reviewed retrospectively. One of two IOL models (SA60AT or MA60AC, Alcon Laboratories, Fort Worth, TX) was implanted in the capsular bag of all eyes. The accuracy of five different IOL formulae, including the BUII, Sanders-Retzlaff-Kraff Theoretical (SRK/T), Holladay I, Hoffer Q and Haigis was evaluated. Constant optimization was performed for each IOL and for each formula separately. Mean prediction error (PE), and the mean and median absolute PE (APE) were calculated for the five different IOL formulae investigated.

Results
The median age at surgery was 74.6 months (IQR, 38.4-110.8 months). The SA60AT IOL was implanted in 41 eyes (18 eyes with AL≤22 mm and 23 eyes with AL>22 mm) and the MA60AC IOL was implanted in 25 eyes (11 eyes with AL≤22 mm and 14 eyes with AL>22 mm). The mean IOL power that was implanted was 23.3 ± 5.1 D (range 12.0 – 39.0 D). Overall, the BUII had a comparable median APE to the Hoffer Q, Holladay I, SRK/T and Haigis formulae (BUII: 0.49D vs. 0.48D, 0.61D, 0.74D and 0.58D, respectively; p=0.205). The BUII, together with Hoffer Q, produced better predictability within 0.5D from target refraction compared with the SRK/T formula (Hoffer Q: 51.5%, BUII: 51.5% vs. SRK/T: 31.8%, p=0.002).

Conclusion
This is the first study to show the results of the BUII formula after constant optimization in the pediatric age group. The BUII formula had comparable accuracy to other tested formulae, and outperformed the SRK/T formula, when calculating IOL power in pediatric eyes undergoing cataract surgery.

Authors

Presenting Author
So Goto, PhD, MD    Email the author
Authors
Naoyuki Maeda, MD, PhD, Tjundewo Lawu, PhD, Ohnuma Kazuhiko, PhD, Toru Noda, MD

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Paper Abstract

Purpose
To demonstrate novel concepts of intraocular lens (IOL) power calculation (O formula) based on ray-tracing without legacy parameters including ultrasound compatible axial length (AL), corneal keratometry readings, and A constant that may affect the postoperative refractive error.

Methods
The study was designed as a retrospective consecutive case series at a single center. A total of 292 eyes implanted with acrylic IOLs between December 2015 to June 2018 were divided into a training set (148 eyes) and a validation set (144 eyes). All biometric data except AL were obtained by anterior-segment swept-source optical coherence tomography (AS-SS-OCT). Manifest refraction, AS-SS-OCT, and SS-OCT-based biometry were conducted preoperatively and 1-month postoperatively. O formula performance was compared with that of the Barrett Universal II (BUII) and SRK/T formulas.

Results
In the training set, MAE of O formula, BUII, and SRK/T were 0.37 ± 0.28 (mean ± SD), 0.37 ± 0.30, and 0.41 ± 0.33 D, respectively. Percentages of patients with refractive prediction error within ±1.00 and ±0.50 D were 99.3% and 83.8% for O formula, 98.0% and 82.4% for BUII, and 96.6% and 75.7% for SRK/T, respectively. In the validation set, MAE of O formula, BUII, and SRK/T were 0.35 ± 0.26, 0.34 ± 0.27, and 0.36 ± 0.27 D, respectively. Percentages of patients with refractive prediction error within ±1.00 and ±0.50 D were 100% and 84.7% for O formula, 98.6% and 86.1% for BUII, and 98.6% and 84.7% for SRK/T, respectively.

Conclusion
The O formula is a promising approach for accurate IOL power calculation using ray-tracing. It can be used as a fail-safe in IOL power calculation, as it is less susceptible to errors associated with legacy parameters.

★ This paper won Best Paper of Session (BPOS) at the 2021 ASCRS Annual Meeting

Authors

Presenting Author
Nicole R. Fram, MD, ABO    Email the author
Authors
John Davidson, MD, ABO, Xiaolin Gu, MD, PhD, Raiju J. Babu, PhD, BScOptom, MSc, Michael J. Breen, OD

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Paper Abstract

Purpose
To demonstrate the effectiveness of the intraoperative aberrometry (IA) with respect to refractive outcomes by comparing its absolute prediction error (APE) and proportion of cases with an APE of 0.50D or less to that from pre-op advanced IOL Formula in post-myopic LASIK cataract eyes

Methods
A retrospective analysis was conducted with the ORA SYSTEM® with AnalyzOR Technology database data from multiple US centers. A minimum of 1000 post-myopic LASIK/PRK eyes implanted with AcrySof® IOLs (SN60WF, SA60WF, SN60AT, SA60AT) and met the inclusion and exclusion criteria were included in the analysis. Primary endpoints included the difference between mean and median APE with IA usage versus preoperative advanced IOL formula calculation. The percentage of cases with APE of 0.50 D or less were also compared between the two IOL power calculation methods.

Results
1067 post myopic LASIK/PRK eyes were analyzed. Mean and median APEs were significantly lower with IA than Barrett True K (BTK) with paired difference of 0.06D and 0.02D respectively (both p<0.001). A significantly higher % of eyes had APEs ≤0.50D with IA (76.2%) than with BTK (69.3%), p<0.0001. For % of eyes with APEs ≤0.25D, IA had a significantly higher % than BTK (47.2%, 42.5% respectively), p=0.013. First surgery eye analysis (n=897) showed similar results. Mean and median APE paired differences were 0.06D and 0.03D respectively, (p<0.0001 for both). The % of eyes with APEs ≤0.50D and ≤0.25D were higher with IA than BTK (75.5% vs. 69.1%, p=0.0004, 46.8% vs. 40.9%, p=0.0037 respectively).

Conclusion
In post myopic LASIK/PRK eyes, the use of intraoperative aberrometry can result in lower mean and median APEs as well as a higher % of eyes with APEs ≤0.50D and ≤0.25D when compared to BTK IOL Formula.

Authors

Presenting Author
Nicole R. Fram, MD, ABO    Email the author
Authors
Graham D. Barrett, FRANZCO, Hasan Alsetri

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Paper Abstract

Purpose
The Barrett True-K and ASCRS IOL calculator are the gold standard in post-refractive IOL calculations without historical data. However, we only achieve +/- 0.50D 63-74% of the time. This study will evaluate the use of IOL master 700 Total Keratometry (TK) and the Barrett True-K-TK vs other formulae to improve post-refractive IOL calculations.

Methods
A retrospective comparative case series was performed for n=27 post myopic LASIK/PRK patients undergoing uncomplicated cataract surgery. Four formula were compared including Haigis L, Shammas, Barrett True-K and Barrett True-K TK. Biometry was performed with the IOL master 700. The Barrett True K-TK was calculated using the IOL master 700 posterior cornea measurements (PK1 and PK2) and displayed by using the TK upgraded software. The outcome measures included Mean and Median Absolute error and percentage of predicted refractive error within 0.5D and 1.0D.

Results
Mean absolute error(MAE)for Haigis L was 0.44D, SD 0.33D; Shammas was 0.39D, SD 0.34D; Barrett True-K was 0.31D, SD 0.26D; and Barrett True-K TK was 0.28D, SD 0.21D. Median absolute error (MedAE) was the following: Haigis L 0.38D; Shammas 0.24D; Barrett True-K 0.24D; and Barrett True-K TK 0.28D. Predicted error within +/-0.50D and +/-1.0D was the following: Haigis L 63%,92.5%; Shammas 70%,96%; Barrett True-K 77%,100%; and Barrett True-K TK 88%,100%, respectively.

Conclusion
Barrett True-K TK improved the percentage of patients with prediction errors within +/- 0.50D by 10% compared to the Barrett True-K with standard K's. The use of the IOL master 700 total keratometry and calculated posterior corneal curvature (PK1 and PK2) measurements resulted in improved accuracy for post-refractive IOL calculations.

Authors

Presenting Author
Masayuki Ouchi, MD, PhD    Email the author

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Paper Abstract

Purpose
To investigate the impact of the implantable collamer lens (ICL) implantation on the intraocular lens (IOL) power calculation and biometric parameters.

Methods
A total of 73 eyes from 37 patients ( mean age: 31.3 years; range: 20-55 years) who underwent ICL implantation were included. The IOL power was calculated before and one month after ICL implantation using three formulae: SRK/T(S), Haigis (H), and Barret Universal 2 (B) with the IOL Master 700. Additionally, the axial length (AL), keratometry (K), and anterior chamber depth (ACD) were measured concurrently using the IOL Master 700 and CASIA2.

Results
The mean IOL power calculation for emmetropia showed low significance post ICL implantation with the H (12.5+/- 4.03 vs 12.2+/-3.89) and B (2.2+/-3.80 vs 12.0+/-3.71) formulae (P<0.01, 0.01), while no significance was observed with S. The ACD measurement using the IOL Master and CASIA2 indicated low significance post ICL implantation compared to before implantation (3.64+/- 0.47 vs 3.32+/- 0.43 and 3.30+/-0.24 vs 3.24+/-0.25) (p<0.01, <0.01), though no significant difference was observed in the AL and K measurements.

Conclusion
In ICL implanted eyes, the S formula might result in a relatively accurate IOL power selection. This is because the S formula does not include ACD as a calculating factor in contrast to the H and B formulae.

Authors

Presenting Author
Pooja Khamar, MD    Email the author
Authors
Tanmay Gupta, MBBS, DOMS, Rohit Shetty, FRCS, Naren Shetty, MS, Abhijit S. Roy, PhD, Luci Kaweri, MD, Ann S. Koshy, MBBS

Paper Abstract

Purpose
To evaluate the Repeatability and agreement between Anterion(Heidelberg Engineering), IOL Master 700 (Carl Zeiss Meditec AG, Germany) and Lenstar 900 (Haag Streit AG,Switzerland) for anterior segment parameters and intraocular lens (IOL) power calculation

Methods
Three measurements were obtained from the three biometers in 127 eyes of 76 patients before cataract surgery and were compared for Axial Length(AL),Central corneal thickness(CCT), Aqueous depth(AD), keratometry (Km) and white to white(WTW).Accuracy of the IOL power measurement as residual error at 1-month post-surgery was also analysed

Results
Mean(SD) of AL,AD,Km&WTW was 23.40(0.007)mm, 2.74(0.007)mm,44.14(0.01)D,11.96(0.01)mm from Lenstar; 23.31(0.16),2.80(0.01), 43.91(0.11),12.11(0.55) from Anterion;23.43(0.025),2.51(0.13),42.74(0.14), 12.07(0.17) from IOL master.Anterion showed systematic differences from both Lenstar & IOL Master for AD & Km.AL showed systematic difference between Lenstar & IOL Master.WTW measurements showed no difference.Mean within-subject standard deviation for AL,AD,Km & WTW was 0.09mm, 0.03mm,0.16D&0.08mm for Anterion,0.017,0.04,0.04&0.05 for Lenstar; 0.03,0.12,0.14;0.17 for IOL Master.Mean(SD) residual refraction at 1 month was -0.06(1.33) for Anterion,-0.07(0.54) for IOL Master & 0.23(0.6) for Lenstar.

Conclusion
Lenstar had the maximum repeatability for the parameters studied, followed by IOL Master and Anterion. The three devices can be used interchangeably for WTW, but not for AL, AD and Km.Anterion had the least IOL prediction error followed by IOL Master and Lenstar