Ocular biometry and refractive outcomes using two swept-source optical coherence tomography-based biometers with segmental or equivalent refractive indices

IOL power calculation in long eyes: Selection of the best axial length adjustement factor using the most common formulas

Purpose

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.

Design

Retrospective, comparative, case-series.

Participants

Patients with long eyes that underwent cataract surgery.

Methods

five-hundred-fifty-four eyes of 554 patients were examined before and after standard phacoemulsification without complications. Eyes were subdivided in 3 groups according to AL: 26.00≤AL<28.00 mm, 28.00≤AL<30.00 mm, AL≥30.00 mm. Eight formulas that do not require anterior chamber depth (ACD) were evaluated: Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO) 2.0, Ladas Super Formula (LSF), Hoffer Q, Holladay 1, SRKT, T2 and T2.2. The lens constant of ULIB database and IOLCon database were used. Each formula was analyzed by using uncorrected AL (ALu) and following AL adjustments: Wang-Koch 1 (wk1), wk2, wk polinomial (wk-pol), estimated Cooke modified axial length (CMALe) and ALc correcting factor.

Main outcome measures

Mean absolute error (MAE), median absolute error (MedAE) and percentage of eyes within ±0.50 and ± 1.00 diopters (D) of prediction error.

Results

T2-ALu gave best outcome when 26.00 mm ≤ AL<28.00 mm. 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 mm ≤ 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≥30.00 mm. 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.

Conclusions

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.

Effect of Intraocular Lens Power Calculation Formula Optimization in the Sum-of-Segments Optical Biometer

Purpose

We evaluated the effect of optimization of the intraocular lens (IOL) power calculation formula SRK/T and Barrett Universal II (BU II) in long eyes (≥26 mm: group L) and short eyes (≤22 mm: group S) using axial length calculated from segmented refractive indices (SRI).

Setting

Multicenter study at five sites in Japan.

Design

Retrospective observational study.

Methods

This study included 461 eyes of 461 patients (mean age 73.8 ± 8.4 years) who underwent cataract surgery. The predicted refractive error (PRE) was compared between the SRI (ARGOS) and the equivalent refractive index (ERI) biometers (IOLMasterTM700). The patients were randomly divided into two groups, a learning group and a validation group. The optimization constants were determined in the learning group, and the optimization constants were subsequently applied to the validation group and compared with the ERI biometer results.

Results

Using both SRK/T and BU II, the validation group's PRE using optimization constants for the SRI biometer in group L was significantly smaller than that using the ERI biometer (p<0.001, p<0.01). In group L, the arithmetic PRE of Barrett UII formula with SRI showed a significant improvement after optimization compared to before optimization (p<0.0001). In group S, the arithmetic PRE of SRK/T and Barrett UII formula with SRI showed a significant improvement (p<0.0001, p<0.0001).

Conclusion

In long and short eyes, the current study revealed that optimization of the SRK/T and Barrett formula constants for the SRI biometer was beneficial to achieve accurate refractive outcomes after cataract surgery.

Refractive Predictability of Two Intraocular Lens Power Formulas in Long, Medium, and Short Eyes Using a Swept Source Optical Coherence Tomography Biometer

Purpose

To compare the refractive predictability of Argos measurements with Barrett Universal II (BUII) and Barrett True Axial Length (BTAL) formulas in a large sample of long, medium, and short axial length (AL) eyes.

Methods

A retrospective chart review identified 445 eyes of 247 patients for inclusion. The Argos was used for preoperative biometry, and BUII formula for intraocular lens (IOL) power calculations. Back calculations were performed using data from the Argos for the BTAL formula. Data were collected for postoperative absolute prediction error (APE), refractive outcomes, and monocular uncorrected and distance corrected visual acuities at distance (UDVA, CDVA).

Results

Overall, mean APE was 0.36 ± 0.33 D for BUII and for 0.34 ± 0.32 D BTAL (p = 0.04). In short AL eyes, mean APE was 0.45 ± 0.37 D for BUII and for 0.37 ± 0.31 D BTAL (p < 0.001). No significant differences between BUII and BTAL were identified for long AL or medium AL eyes. The percentages of eyes with APE of 0.5 D or less in long, medium, and short eyes were 79%, 79% and 51%, respectively, for BUII and 82%, 78% and 69%, respectively, for BTAL.

Conclusion

The prediction accuracies were high with both the BUII and BTAL formulas in long, medium, and short eyes, leading to excellent refractive outcomes. The BTAL formula may have lower absolute prediction error in short eyes compared to BUII.

Comparison of the IOL Master and Pentacam in the measurement of anterior segment parameters in patients with high myopia and cataracts

PURPOSE

This study aimed to compare the differences between the Zeiss IOL Master and Oculus Pentacam in keratometry and central anterior chamber depth (ACD) measurements in patients with high myopia and cataracts.

METHODS

Between January 2019 and December 2020, 89 patients (103 eyes) with cataracts and high myopia who underwent preoperative cataract evaluation at Nanchang First Hospital were selected for retrospective analysis. Keratometry (K1, K2) and ACD were measured with the IOL Master and Pentacam. Paired t-tests were performed to compare the differences, while the Bland-Altman method was used to evaluate the agreement.

RESULTS

The K1 value was (43.15±2.44) D for the IOL Master and (42.98±2.47) D for the Pentacam, and the difference between the two instruments was statistically significant (P<0.01). The K2 value was (44.55±2.63) D for the IOL Master and (44.32±2.55) D for the Pentacam. The ACD was (3.44±0.33)mm for the IOL Master and (3.39±0.36)mm for the Pentacam. There were statistically significant differences between the two instruments in both keratometry and ACD (P<0.01). The absolute values of the maximum difference between the two instruments for K1 and K2 were 1.1 and 1.07; thus, the consistency of the two instruments with respect to this measurement was poor. However, the absolute value of the maximum difference between the two instruments for ACD was 0.34, so the consistency of the two instruments in relation to this measurement was good.

CONCLUSIONS

Both the IOL Master and the Pentacam can be used in the measurement of keratometry and ACD in patients with high myopia and cataracts, but the keratometry measurements should be compared in clinical application.

Accuracy Validation of the New Barrett True Axial Length Formula and the Optimized Lens Factor Using Sum-of-Segment Biometry

Objectives: This study aims to verify the accuracy of a new calculation formula, Barrett true axial length formula (T-AL), and the optimized lens factor (LF) for predicting postoperative refraction after cataract surgery. Methods: We included 156 Japanese patients who underwent cataract surgery using Clareon monofocal intraocular lenses at our clinic between January 2022 and June 2023. Postoperative spherical equivalent was calculated using subjective refraction values obtained 1 month post-surgery. The LFs were optimized so that the mean prediction error (PE) of each calculation formula was zero (zero optimization). We calculated the mean absolute PE (MAE) to assess accuracy and used a Friedman test for statistical comparisons. The accuracy of T-AL and the optimized LFs was compared with that of the conventional Barrett Universal II formula for ARGOS (AR-B) and OA-2000 (OA-B) with equivalent refractive index. Results: For T-AL, AR-B, and OA-B, the MAEs ± standard deviations were 0.225 ± 0.179, 0.219 ± 0.168, and 0.242 ± 0.206 D, respectively. The Friedman test showed no statistically significant differences among the three groups. The device-optimized LFs were 2.248-2.289 (T-AL), 2.236-2.246 (AR-B), and 2.07-2.08 (OA-B); the corresponding zero-optimized LFs were 2.262-2.287 (T-AL), 2.287-2.303 (AR-B), and 2.160-2.170 (OA-B). Conclusion: There were no significant differences in prediction accuracy among the formulas. However, the accuracy of LF optimization varied by device, with T-AL being closest to the value under zero optimization. This suggests that T-AL is clinically useful for predicting an accurate postoperative refraction without zero optimization.

Evaluation of Selected Biometric Parameters in Cataract Patients-A Comparison between Argos® and IOLMaster 700®: Two Swept-Source Optical Coherence Tomography-Based Biometers

Background and Objectives: To compare the biometry of eyes obtained with two swept-source optical coherence tomography-based biometers-Argos (A), using an individual refractive index, and IOLMaster 700 (IM), using an equivalent refractive index-for all structures. Materials and Methods: The biometry of 105 eyes of 105 patients before cataracts were analyzed in this study. Parameters such as axial length (AL), anterior chamber depth (ACD), and lens thickness (LT) were compared from both devices. According to the axial length measurements, patients were divided into three groups, as follows: group 1-short eyes (AL < 22.5 mm), group 2-average eyes (22.5 ≤ AL ≤ 26.0 mm), and group 3-long eyes (AL > 26.0 mm). Results: The correlation coefficiency among all compared parameters varies from R = 0.92 to R = 1.00, indicating excellent reliability of IM and A. A statistical significance in axial length was indicated in the group of short eyes (n = 26)-mean AL (A) 21.90 mm (±0.59 mm) vs. AL (IM) 21.8 mm ± (0.61 mm) (p < 0.001)-and in the group of long eyes (n = 5)-mean AL (A) 27.95 mm (±2.62 mm) vs. mean AL (IM) 28.10 mm (±2.64) (p < 0.05). In the group of average eyes (n = 74), outcomes were similar-mean AL (A) 23.56 mm (±0.70 mm) vs. mean AL (IM) 23,56 mm (±0.71 mm) (p > 0.05). The anterior chamber depth measurements were higher when obtained with Argos than with IOLMaster 700-mean ACD (A) 3.06 mm (±0.48 mm) vs. mean ACD (IM) 2.92 mm (±0.46) p < 0.001. There was no statistical significance in mean LT-mean LT (A) 4.75 mm (±0.46 mm) vs. mean LT (IM) 4.72 mm (±0.44 mm) (p = 0.054). The biometry of one eye with dense cataracts could be measured only with Argos, using the Enhanced Retinal Visualization mode. Conclusions: Axial length measurements from both devices were different in the groups of short and long eyes, but were comparable in the group of average eyes. The anterior chamber depth values obtained with Argos were higher than the measurements acquired with IOLMaster 700. These differences may be particularly important when selecting IOLs for patients with extreme AL values.

Current Concepts and Recent Updates of Optical Biometry- A Comprehensive Review

One of the most recent advancements in the field of cataract surgery is optical biometry. With the advent of optical biometry ocular measurements are now simpler, quicker, and more precise. The devices have made intraocular lens (IOL) power calculations easier in difficult situations too, such as in cases with extremes of axial lengths, silicone filled eyes, cataract surgery in post-keratoplasty eyes, post Laser-Assisted in Situ Keratomileusis (LASIK) eyes, etc. The gold standard for IOL power calculation in the present day is by the use of optical biometry devices. The anatomical measurements by these devices are highly precise and because of these measurements and the incorporation of various IOL power calculation formulas the optical biometry devices give the accurate power and the post-operative visual outcome is highly satisfactory among the patients. The growing use of these devices has made cataract the most commonly performed refractive surgical procedure nowadays. In the current scenario, optical biometry has widespread acceptance in almost all countries and has many advantages over ultrasound or immersion biometry. Cataract surgeons can obtain easy and reliable measurements from these devices. Refractive surprises have also decreased considerably with their use. This article will comprehensively review the principles of the various optical biometry devices, the parameters used in each of the devices, the advantages and disadvantages, and add more like what all this article will add.

Evaluation of a new dynamic real-time visualization 25 kHz swept-source optical coherence tomography based biometer

BACKGROUND

To evaluate the intraobserver repeatability and interobserver reproducibility of a newly developed dynamic real-time visualization 25 kHz swept-source optical coherence tomography (SS-OCT) based biometer (ZW-30, TowardPi Medical Technology Ltd, China) and compare its agreement with another SS-OCT based biometer (IOLMaster 700, Carl Zeiss Meditec AG, Jena, Germany).

METHODS

Eighty-two healthy right eyes were enrolled in this prospective observational study. Measurements were repeated for three times using the ZW-30 and IOLMaster 700 in a random order. Obtained parameters included axial length (AL), central corneal thickness (CCT), aqueous depth (AQD), anterior chamber depth (ACD), lens thickness (LT), mean keratometry (Km), astigmatism magnitude (AST), vector J0, vector J45, and corneal diameter (CD). The within-subject standard deviation (Sw), test-retest (TRT) variability, coefficient of variation (CoV), and intraclass correlation coefficient (ICC) were adopted to assess the intraobserver repeatability and interobserver reproducibility. The double-angle plot was also used to display the distribution of AST. To estimate agreement, Bland-Altman plots were used.

RESULTS

For the intraobserver repeatability and interobserver reproducibility, the Sw, TRT and CoV for all parameters were low. Meanwhile, the ICC values were all close to 1.000, except for the J45 (ICC = 0.887 for the intraobserver repeatability). The double-angle plot showed that the distribution of AST measured by these two devices was similar. For agreement, the Bland-Altman plots showed narrow 95% limits of agreements (LoAs) for AL, CCT, AQD, ACD, LT, Km AST, J0, J45, and CD (- 0.02 mm to 0.02 mm, - 7.49 μm to 8.08 μm, - 0.07 mm to 0.04 mm, - 0.07 mm to 0.04 mm, - 0.07 mm to 0.08 mm, - 0.16 D to 0.30 D, - 0.30 D to 0.29 D, - 0.16 D to 0.16 D, - 0.23 D to 0.13 D, and - 0.39 mm to 0.10 mm, respectively).

CONCLUSIONS

The newly dynamic real-time visualization biometer exhibited excellent intraobserver repeatability and interobserver reproducibility. The two devices both based on the SS-OCT principle had similar ocular parameters measurement values and can be interchanged in clinical practice.

Efficacy of the DRL orthokeratology lens in slowing axial elongation in French children

Background

This study aims to assess and compare the impact of Orthokeratology Double Reservoir Lens (DRL) versus Single Vision Lenses (SVL) on axial elongation and anterior chamber biometric parameters in myopic children over a 6- and 12-month treatment period in France.

Methods

A retrospective study involving 48 patients aged 7 to 17 years, who underwent either orthokeratology treatment or single-vision spectacle correction, was conducted. Changes in refractive error, axial length, and anterior chamber depth were examined.

Results

Twenty-five patients comprised the Orthokeratology (OK) group, while twenty-three were in the control group (single-vision spectacle group). Significant increases in mean axial length were observed over time in both the control (0.12 ± 0.13 mm and 0.20 ± 0.17 mm after 6 and 12 months, respectively; F (2,28.9) = 27.68, p < 0.001) and OK groups (0.02 ± 0.07 mm and 0.06 ± 0.13 mm after 6 and 12 months, respectively; F (2,29.1) = 5.30, p = 0.023). No statistically significant differences in axial length were found between male and female children (p > 0.620). Age-specific analysis revealed no significant axial elongation after 12 months in the 14-17 years group in the OK group. Anterior biometric data analysis at 6 and 12 months showed statistical significance only for the DRL group.

Conclusion

Orthokeratology resulted in an 86 and 70% reduction in axial elongation after 6 and 12 months of lens wear, respectively, compared to the single-vision spectacles group. Myopia progression was more pronounced in younger children, underscoring the importance of initiating myopia control strategies at early ages.

Refractive Predictability of a Swept Source Optical Coherence Tomography Biometer in Long and Short Eyes Implanted with Extended Depth of Focus Intraocular Lenses

Purpose

To determine the refractive predictability of Argos (Movu, a Santec company) measurements and the Barrett Universal II formula in long and short eyes implanted with an extended depth of focus (EDOF) intraocular lens (IOL).

Methods

This retrospective, non-interventional study included 86 eyes (55 long and 31 short) of 55 patients. Preoperative biometry was performed using the Argos. Preoperative IOL power formulas were the preprogrammed Barrett Universal II (BUII). Data were collected for refractive outcomes, postoperative prediction error (directional and absolute), and monocular corrected distance visual acuity (CDVA, Snellen).

Results

The mean absolute prediction error for BUII was 0.27 ± 0.26 D overall, 0.24 ± 0.20 D in long eyes, and 0.33 ± 0.33 D in short eyes. Overall, the percentage of eyes with ≤ 0.5 D prediction error was 84% for BUII. In long eyes, the percentage of eyes with ≤ 0.5 D prediction error was 90% for BUII. In short eyes, the percentage of eyes with ≤ 0.5 D prediction error was 74% for BUII. The percentage of eyes with ≤ 0.5 D of MRSE was 89% for long eyes and 94% for short eyes. Visual acuities were excellent in both long and short eyes, with > 90% of eyes 20/25 or better in each group.

Conclusion

The prediction error of Argos using BUII was low in long and short eyes at one month after EDOF IOL implantation.

Randomized Trial Comparing Prediction Accuracy of Two Swept Source Optical Coherence Tomography Biometers

Purpose

To compare the prediction accuracy of the Argos biometer using standard keratometry to the prediction accuracy of the IOLMaster 700 biometer using Total Keratometry.

Methods

This was a randomized, prospective, single surgeon study of 80 right eyes of 80 patients that had preoperative biometry with both the Argos and IOLMaster 700 devices, followed by cataract surgery and intraocular lens (IOL) implantation. Prediction errors (directional and absolute) for each device were determined from the 1 month postoperative manifest refraction.

Results

The directional prediction error was 0.07 ± 0.32 D for the Argos and 0.08 ± 0.34 D for the IOLMaster 700. The mean of the difference in prediction error (directional) was 0.02 D, which was not statistically significant (p > 0.05). The absolute prediction error was 0.21 ± 0.25 D for the Argos and 0.25 ± 0.24 D for the IOLMaster 700. The mean of the difference in absolute prediction error was 0.04 D, which was statistically significant (p < 0.004) but not clinically significant. The percentage of eyes with absolute prediction error ≤ 0.5 D was 91% (73 eyes) for the Argos and 88% (70 eyes) for the IOLMaster 700. This difference was not statistically significant.

Conclusion

The prediction accuracies were similar between the Argos and IOLMaster 700 in eyes with normal axial length. There was a significant difference in mean absolute prediction error between devices; however, this was not clinically meaningful.

Comparing Predictive Accuracy of a Swept Source Optical Coherence Tomography Biometer and an Optical Low Coherence Reflectometry Biometer

Purpose

To compare the refractive accuracy resulting from calculations based on measurements with a swept-source optical coherence tomography (SS-OCT) biometer compared to calculations based on measurements with an optical low coherence reflectometry (OLCR) biometer at one month postoperatively.

Methods

This was a retrospective comparative non-interventional study of preoperative biometry and postoperative refraction and visual acuity of 200 eyes. All eyes had preoperative biometry with both the Argos (Movu, a Santec company) and Lenstar LS900 (Haag-Streit AG) devices. Data were collected for mean postoperative prediction error (directional and absolute), preoperative mean K, delta K (corneal astigmatism), axial length, and anterior chamber depth.

Results

The mean directional prediction error was -0.15 ± 0.47 D for Argos and -0.31 ± 0.50 D for Lenstar LS900, and there was a statistically significant mean of the differences (0.16 ± 0.24 D; p < 0.001). The mean absolute prediction error was 0.35 ± 0.34 D for Argos and 0.42 ± 0.41 D for Lenstar LS900, and there was a statistically significant mean of the differences (-0.07 ± 0.24 D; p < 0.001). Neither the differences in directional prediction error nor the differences in absolute prediction error were clinically significant.

Conclusion

The directional and absolute prediction accuracies were statistically significant, but not clinically different between the Argos and Lenstar LS900 devices. In addition, differences between preoperative K, AL, and ACD measurements were not clinically significant.

Refractive Predictability and Biometry Agreement of a Combined Swept Source Optical Coherence and Reflectometry Biometer Compared to an Optical Low Coherence Reflectometry Biometer and an SS-OCT Biometer

Purpose

To evaluate the agreement of refractive predictability of a swept-source optical coherence tomography (SS-OCT) biometer, which uses segmental AL calculation, with another SS-OCT biometer, and an optical low coherence reflectometry (OLCR) biometer. The secondary objective was to describe the refractive outcomes, visual acuities, and the agreement of different preoperative biometric parameters.

Patients and Methods

The study was a retrospective one-arm study of refractive and visual outcomes after successful cataract surgery. Preoperative biometric data were collected with two different SS-OCT device (Argos, Alcon Laboratories and Anterion, Heidelberg Engineering) and an OLCR device (Lenstar 900, Haag-Streit). The Barrett Universal II formula was used to calculate IOL power for all three devices. Follow-up examination was 1-2 months after surgery. The main outcome measure, refractive prediction error (RPE), was calculated as the achieved postoperative refraction minus the predicted refraction for each device. Absolute error (AE) was calculated by reducing the mean error to zero.

Results

The study included 129 eyes of 129 patients. The mean RPE was 0.06, -0.14 and 0.17 D for the Argos, Anterion and Lenstar, respectively (p < 0.01). The Argos also had the lowest absolute RPE, while the Lenstar had the lowest median AE, but this was not statistically significant (p > 0.2). The percentages of eyes with RPE within ±0.5 was 76%, 71%, and 78% for the Argos, Anterion, and Lenstar, respectively. The percentages of eyes with AE within 0.5 D was 79%, 84%, and 82% for the Argos, Anterion and Lenstar, respectively. None of these percentages were statistically significantly different (p > 0.2).

Conclusion

All three biometers showed good refractive predictability with no statistically significant differences in AE or percentages of eyes within ± 0.5 D of RPE or AE. The lowest arithmetic RPE was found with the Argos biometer.

Evaluation and comparison of ocular biometric parameters obtained with Tomey OA-2000 in silicone oil-filled aphakic eyes

PURPOSE

To evaluate a new non-contact instrument (OA-2000) measuring the ocular biometry parameters of silicone oil (SO)-filled aphakic eyes, as compared with IOLMaster 700.

METHODS

Forty SO-filled aphakic eyes of 40 patients were enrolled in this cross-sectional clinical trial. The axial length (AL), central corneal thickness (CCT), keratometry ((flattest keratometry) Kf and (steep keratometry, 90° apart from Kf) Ks), and axis of the Kf (Ax1) were measured with OA-2000 and IOLMaster 700. The coefficient of variation (CoV) was calculated to assess the repeatability. The correlation was evaluated by the Pearson coefficient. Bland-Altman analysis and paired t test were used to analyze the agreements and differences of parameters measured by the two devices, respectively.

RESULTS

The mean AL obtained with the OA-2000 was 23.57 ± 0.93 mm (range: 21.50 to 25.68 mm), and that obtained with the IOLMaster 700 was 23.69 ± 0.94 mm (range: 21.85 to 25.86 mm), resulting in a mean offset of 0.124 ± 0.125 mm (p < 0.001). The mean offset of CCT measured by OA-2000 and IOLMaster 700 was 14.6 ± 7.5 μm (p < 0.001). However, the Kf, Ks and Ax1 values from the two devices were comparable (p > 0.05). All the measured parameters of the two devices showed strong linear correlations (all r ≥ 0.966). The Bland-Altman analysis showed a narrow 95% limits of agreement (LoA) of Kf, Ks and AL, but 95%LoA of CCT and Ax1 was wide, which were - 29.3 ~ 0.1 μm and-25.9 ~ 30.7°respectively. The CoVs of the biometric parameters obtained with OA-2000 were lower than 1%.

CONCLUSION

In SO-filled aphakic eyes, the ocular parameters (including AL, Kf, Ks, Ax1, and CCT) measured by the OA-2000 and IOLMaster 700 had a good correlation. Two devices had an excellent agreement on ocular biometric measurements of Kf, Ks and AL. The OA-2000 provided excellent repeatability of ocular parameters in SO-filled aphakic eyes.

Factors contributing to long-term refractive error after cataract surgery

PURPOSE

To evaluate factors that may influence the direction and extent of long-term refractive error after cataract surgery.

METHODS

This was a retrospective observational study conducted across two private practices in Sydney, NSW, Australia. The study population consisted of patients who underwent cataract phacoemulsification surgery between January 1 and December 31, 2018. Patients who received cataract surgery combined with another procedure were excluded. Demographic and biometric data including anterior chamber depth (ACD), keratometry, central corneal thickness, axial length (AL) and lens thickness were obtained pre-operatively. Spherical equivalent (SEQ) refraction was measured at 2 months and 3 years after surgery and compared with target refraction. Factors associated with refractive error were analyzed.

RESULTS

This study included 221 eyes of 122 patients. A refractive error within 1.00 D was achieved in 217 eyes (98.2%) at 3 years post-operatively. Mean prediction error decreased significantly between 2 months and 3 years after surgery irrespective of whether eyes were more myopic (p < 0.001) or more hypermetropic than predicted (p < .0001). Pre-operative ACD and ACD-to-AL ratio were significantly associated with SEQ prediction error.

CONCLUSION

After cataract surgery, refractive outcomes may be influenced by ACD and ACD-to-AL ratio. The pre-operative assessment of these risk factors may better inform IOL selection in individual patients. Prospective studies in a larger cohort are required.

Cataract surgery in adult eyes with short axial length

PURPOSE OF REVIEW

Cataract surgery in eyes of patients with short axial length (AL) can be technically challenging and is associated with a high risk of intra- and postoperative complications. Several technical and surgical strategies have been proposed to optimize the visual outcome and decrease the rate of surgical complications and it is important to understand their applications in these cases.

RECENT FINDINGS

Traditional intraocular lens (IOL) measurement formulas in eyes with short AL have reduced reliability. Novel formulas such as the Kane formula provide a better refractive prediction. Surgery can be difficult in short eyes due to the crowdedness of the anterior chamber (AC) and the associated scleral abnormalities increasing the risk of uveal effusion. Surgical techniques such as prophylactic scleral incisions, limited pars plana anterior vitrectomy, and modified hydrodissection, have been shown to facilitate surgery in extremely short eyes and decrease the rate of operative complications. Although cataract surgery improves vision in these cases, short AL and shallow AC have been associated with worse visual outcomes.

SUMMARY

Newer 4 th generation IOL formulas have improved the refractive outcomes of cataract surgery in eyes with short AL. There are multiple evolving surgical strategies for optimizing surgery in these eyes. However, studies on the surgical and visual outcomes of cataract surgery in eyes with short AL are limited by their design and sample size. With further research and continued clinical experiences, we hope to develop evidence-based algorithms for the management of these complex cases.

Split-Window OCT biometry in pseudophakic eyes

PURPOSE

To determine the utility of Split-Window optical coherence tomography OCT (SW-OCT) biometry in measuring ocular axial dimensions as well as imaging the intraocular lens (IOL) and posterior capsule in pseudophakic eyes.

METHODS

Sixty-nine pseudophakic eyes of 69 subjects were enrolled in the study. The results of SW-OCT biometry implemented in the SD OCT device for posterior and anterior segment imaging (REVO NX, Optopol Technology) were compared with those obtained with the SS-OCT-based biometer IOLMaster 700 (Carl Zeiss Meditec). Differences in measurement values between the two biometers were determined using the paired t-test. Agreement was assessed through intraclass correlation coefficients (ICC) and Bland-Altman plots.

RESULTS

The correlation between measurements obtained with SW-OCT and SS-OCT was very high (ICC for: axial length (AL) = 1.000; anterior chamber depth (ACD) = 0.997; IOL thickness (IOL LT) = 0.997; central corneal thickness (CCT) = 0.987). The mean AL measurement difference was 0.003 ± 0.021 mm (the 95% LoA ranged from -0.04 to 0.05); the mean ACD difference was -0.009 ± 0.025 mm (95% LoA, -0.06 to 0.04); mean LT difference was 0.001 ± 0.021 mm (95% LoA, -0.04 to 0.04); and mean CCT difference was 1.4 ± 5.4 μm (95% LoA, -9 to 12).

CONCLUSION

The study shows small, non-significant differences between the biometric measurements obtained with REVO NX SW-OCT and IOLMaster 700 SS-OCT in pseudophakic eyes. However, SW-OCT offered significantly lower ACD and LT measurement failure rates. With high-resolution imaging, SW-OCT enables accurate assessment of IOL position relative to the posterior capsule and visualization of capsular fibrosis.

Comparison of Astigmatism Prediction Accuracy for Toric Lens Implantation from Two Swept-Source Optical Coherence Tomography Devices

Purpose

To compare the astigmatism prediction accuracy for toric intraocular lens (IOL) implantation between two swept-source optical coherence tomography (SS-OCT) devices: Argos (Movu, a Santec Company) and the IOLMaster 700 (Carl Zeiss Meditec).

Methods

This was a retrospective chart review of 59 eyes (44 patients) with corneal astigmatism and cataract that underwent cataract surgery or refractive lens exchange surgery with a toric IOL. Biometry was performed on all patients prior to cataract surgery and the Barrett toric IOL calculator was used. Visual acuity was measured postoperatively. Manifest refraction was measured at 1 month and compared to the predicted postoperative residual refraction. Preoperative K measurements between devices were also compared.

Results

Mean cylinder prediction error was −0.17 ± 0.43 for Argos and 0.12 ± 0.56 for IOLMaster 700. The cylinder prediction error 0.5 D or less was not significantly different between the devices, with 83.1% (49 eyes) for Argos and 76.3% (45 eyes) for IOLMaster 700 (p = 0.206). Spherical equivalent prediction error was 0.13 ± 0.39 for Argos and 0.25 ± 0.50 for IOLMaster 700. The mean spherical equivalent prediction error 0.5 D or less was significantly different between the devices, with 79.7% (47 eyes) for Argos and 61.0% (36 eyes) for IOLMaster 700 (p = 0.016).

Conclusion

The prediction accuracies were similar between the devices, except for spherical equivalent, where a higher percentage of eyes were 0.5 D or less of the prediction with the Argos compared to the IOLMaster.

Accuracy of newer intraocular lens power formulas in short and long eyes using sum-of-segments biometry

PURPOSE

To analyze the accuracy of newer intraocular lens power formulas in long and short eyes measured using the sum-of-segments biometry.

SETTING

Private practice, Lynwood, California.

DESIGN

Retrospective observational study.

METHODS

595 patients scheduled for cataract surgery had their eyes measured using the sum-of-segments biometry. The expected residual refractions were calculated using Barrett Universal II (B II), Barrett True Axial Length (BTAL), Emmetropia Verifying Optical (EVO), Hill-RBF, Hoffer QST, Holladay 2, Holladay 2-NLR, K6, Kane, Olsen, PEARL-DGS, T2, and VRF formulas and compared with the traditional Haigis, Hoffer Q, Holladay 1, and SRK/T formulas.

RESULTS

In the 102 long eyes, all new formulas had a mean absolute error (MAE) equal or lower than the traditional formulas, ranging from 0.29 to 0.32 diopter (D). In the 78 short eyes, BTAL, EVO, Hoffer QST, K6, Olsen, and PEARL-DGS formulas had the lowest MAE (0.33 D, 0.33 D, 0.31 D, 0.36 D, 0.32 D, and 0.32 D, respectively), whereas all traditional formulas exceeded 0.36 D.

CONCLUSIONS

All new formulas performed equal or better than the traditional formulas with the sum-of-segments biometry. The best overall results in the short and long eyes as well as in the very short and very long eyes were noted with the BTAL, EVO, Hoffer QST, K6, Olsen, and PEARL-DGS formulas, closely followed by the B II and Kane formulas.

Investigating the Prediction Accuracy of Recently Updated Intraocular Lens Power Formulas with Artificial Intelligence for High Myopia

The aim of this study was to investigate the prediction accuracy of intraocular lens (IOL) power formulas with artificial intelligence (AI) for high myopia. Cases of highly myopic patients (axial length [AL], >26.0 mm) undergoing uncomplicated cataract surgery with at least 1-month follow-up were included. Prediction errors, absolute errors, and percentages of eyes with prediction errors within ±0.25, ±0.50, and ±1.00 diopters (D) were compared using five formulas: Hill-RBF3.0, Kane, Barrett Universal II (BUII), Haigis, and SRK/T. Seventy eyes (mean patient age at surgery, 64.0 ± 9.0 years; mean AL, 27.8 ± 1.3 mm) were included. The prediction errors with the Hill-RBF3.0 and Kane formulas were statistically different from the BUII, Haigis, and SRK/T formulas, whereas there was not a statistically significant difference between those with the Hill-RBF3.0 and Kane. The absolute errors with the Hill-RBF3.0 and Kane formulas were smaller than that with the BUII formula, whereas there was not a statistically significant difference between the other formulas. The percentage within ±0.25 D with the Hill-RBF3.0 formula was larger than that with the BUII formula. The prediction accuracy using AI (Hill-RBF3.0 and Kane) showed excellent prediction accuracy. No significant difference was observed in the prediction accuracy between the Hill-RBF3.0 and Kane formulas.

Intraocular lens power calculation in patients with irregular astigmatism

PURPOSE

Accurate intraocular lens (IOL) calculation in subjects with irregular astigmatism is challenging. This study evaluated the accuracy of using Scheimpflug-derived central 2-mm equivalent keratometry reading (EKR) values for IOL calculation in irregular astigmatism.

METHODS

This retrospective study included subjects (31 eyes of 30 patients) who underwent cataract surgery and IOL calculation using the 2-mm central EKR methods. We compared prediction error (PE) and absolute PE (APE) outcomes using SRK/T and Barrett Universal II formulas for keratometry data obtained from the IOLMaster 500 and Pentacam (anterior corneal sim k) devices.

RESULTS

Cataract surgery and IOL calculation using the 2-mm central EKR methods resulted in improved visual acuity (uncorrected: from 1.13 ± 0.38 to 0.65 ± 0.46 logMar, p < 0.01; best-corrected: from 0.45 ± 0.24 to 0.26 ± 0.20 logMar, p < 0.01) after surgery. The percentage of subjects with best-corrected visual acuity of 6/6 was 22%, < 6/9 was 58%, and < 6/12 was 71%. For both the SRK/T and the Barrett formulas, the PE was similar to those obtained by IOLMaster (> 0.14) but lower than those obtained by the anterior corneal sim k (p < 0.02). IOLMaster provided keratometry reading in only 23/31 (74.1%) of cases.

CONCLUSIONS

The use of Scheimpflug central 2-mm EKR for IOL calculation in irregular astigmatism was beneficial in terms of visual acuity improvement. It had comparable refractive prediction performance to the IOLMaster 500 and better than the anterior corneal sim K. The 2-mm EKR method can be used when IOLMaster cannot provide a reliable reading in abnormal corneas.

Retinal magnification factors at the fixation locus derived from schematic eyes with four individualized surfaces

Retinal magnification factors (RMFs) allow the conversion of angles to lengths in retinal images. In this work, we propose paraxial and non-paraxial RMF calculation methods that incorporate the individual topography and separation of the anterior and posterior surfaces of the cornea and crystalline lens, assuming homogeneous ocular media. Across 34 eyes, the two RMF methods differ by 0.1% on average, due to surface tilt, decenter, and lack of rotational symmetry in the non-paraxial modeling, which results in up to 2.2% RMF variation with retinal meridian. Differences with widely used individualized RMF calculation methods are smallest for eyes with ∼24 mm axial length, and as large as 7.5% in a 29.7 mm long eye (15D myope). To better model the capture of retinal images, we propose the tracing of chief rays, instead of the scaling of posterior nodal or principal distances often used in RMF definitions. We also report that RMF scale change is approximately proportional to both refractive error and axial separation between the ophthalmoscope's exit pupil and the eye's entrance pupil, resulting in RMF changes as large as 13% for a 1cm displacement in a 15D myopic eye. Our biometry data shows weak correlation and statistical significance between surface radii and refractive error, as well as axial length, whether considering all eyes in the study, or just the high myopes, defined as those with refractive error sphere equivalent ≤ -4D. In contrast, vitreous thicknesses show a strong correlation (r ≤ -0.92) and significance (p ≤ 10-13) with refractive error when considering all eyes or just high myopes (r ≤ -0.95; p ≤ 10-5). We also found that potential RMF change with depth of cycloplegia and/or residual accommodation is smaller than 0.2%. Finally, we propose the reporting of individual ocular biometry data and a detailed RMF calculation method description in scientific publications to facilitate the comparison of retinal imaging biomarker data across studies.

Comparison Study of the Two Biometers Based on Swept-Source Optical Coherence Tomography Technology

This research aimed to investigate the potential differences in the parameters, including axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), flat keratometry (Kf), steep keratometry (Ks), mean keratometry (Km), astigmatism, white-to-white (WTW) distance, acquired rate, and intraocular lens (IOL) power, between the two swept-source optical coherence tomography (SS-OCT) biometers, the ANTERION (biometer A) and IOLMaster 700 (biometer B). In a prospective observational comparative case series study, we enrolled 198 eyes undergoing cataract surgery. The AL, CCT, ACD, LT, Kf, Ks, Km, astigmatism, WTW, acquired rate, and IOL power were assessed. McNemar tests compared the acquired rate, and the paired sample t-test compared the quantitative measurement results between the groups. Nineteen eyes were excluded owing to missing AL data for either biometer. Finally, data from 179 eyes were analyzed. Between the two devices, no significant difference was found in AL, astigmatism magnitude, J0, and J45, while significant differences existed in CCT, ACD, LT, Kf, Ks, Km, WTW, astigmatism axis, and IOL power; no statistical significance was found in the AL acquired rate (biometer A, 90.9% and biometer B, 93.9%). Approximately 65.4% of eyes demonstrated ≥0.5-D difference in IOL power between the two biometers. In conclusion, the two biometers showed significant differences in all measurements (CCT, ACD, LT, K, WTW, astigmatism axis, and IOL power), except for AL.

IOL power calculation with ray tracing based on anterior segment OCT and adjusted axial length after myopic excimer laser surgery

PURPOSE

To report the results of intraocular lens (IOL) power calculation by ray-tracing in eyes with previous myopic excimer laser surgery.

SETTING

G.B. Bietti Foundation I.R.C.C.S., Rome, Italy.

DESIGN

Retrospective interventional case series.

METHODS

A series of consecutive patients undergoing phacoemulsification and IOL implantation after myopic excimer laser was investigated. IOL power was calculated using ray-tracing software available on the anterior segment optical coherence tomographer MS-39 (CSO, Italy). Axial length (AL) was measured by optical biometry and 4 values were investigated: 1) that from the printout, 2) the modified Wang/Koch formula, 3) the polynomial equation for the Holladay 1 and 4) for the Holladay 2 formula. The mean prediction error (PE), median absolute error (MedAE), percentage of eyes with a PE within ±0.50 diopters (D) were reported.

RESULTS

We enrolled 39 eyes. Entering the original AL into ray-tracing led to a mean hyperopic PE (+0.56 ±0.54 D), whereas with the Wang/Koch formula a mean myopic PE (-0.41 ±0.53D) was obtained. The Holladay 1 and 2 polynomial equations lead to the lowest PEs (-0.10 ±0.49 and +0.08 ±0.49 D respectively), lowest MedAE (0.37 and 0.25 D) and highest percentages of eyes with a PE within ±0.50 D (71.79 and 76.92%). Calculations based on the Holladay 2 polynomial equation showed a statistically significant difference compared to other methods used (including Barrett-True K formula), with the only exception of the Holladay 1 polynomial equation.

CONCLUSIONS

IOL power can be accurately calculated by ray-tracing with adjusted AL according to the Holladay 2 polynomial equation.

COMPARISON OF OPTICAL BIOMETERS ARGOS AND IOL MASTER 700

PURPOSE

To compare the biometric data obtained by the new optical biometer Argos and the conventionally used biometer IOL Master 700.

PATIENTS AND METHODS

Retrospective analysis of the biometric data of 57 patients (106 eyes) who were examined at TANA Ophthalmology Clinic s.r.o in Olomouc. Patient measurements were carried out on both devices on the same day by the same optometrist within the standard preoperative calculation of the intraocular lens before cataract surgery. Evaluated and statistically analyzed biometric data were axial lenght, anterior chamber depth, average keratometry and lens thickness.

RESULTS

The correlation between all compared data was high, with statistical significance p &lt; 0.01. Bland-Altman plots showed good agreement with a 95% limit of agreement. Axial lenght, average keratometry and lens thickens did not show significant differences (p = 0.941; p = 0.773; p = 0.860). IOL Master 700 showed flatter average keratometry, however, the differences were numerically small and insignificant. Anterior chamber depths obtained by Argos were longer, with a significance p &lt; 0.05.

CONCLUSION

The segmental refractive index technology used by Argos caused differences in anterior chamber depths. Overall axial length was, however, not, in our cohort of patients, affected by this. In general, the optical biometers Argos and IOL Master 700 show excellent agreement in the measured biometric data.

Refractive Outcomes after Cataract Surgery

A post-operative manifest refractive error as close as possible to target is key when performing cataract surgery with intraocular lens (IOL) implantation, given that residual astigmatism and refractive errors negatively impact patients’ vision and satisfaction. This review explores refractive outcomes prior to modern biometry; advances in biometry and its impact on patients’ vision and refractive outcomes after cataract surgery; key factors that affect prediction accuracy; and residual refractive errors and the impact on visual outcomes. There are numerous pre-, intra-, and post-operative factors that can influence refractive outcomes after cataract surgery, leaving surgeons with a small “error budget” (i.e., the source and sum of all influencing factors). To mitigate these factors, precise measurement and correct application of ocular biometric data are required. With advances in optical biometry, prediction of patient post-operative refractory status has become more accurate, leading to an increased proportion of patients achieving their target refraction. Alongside improvements in biometry, advancements in microsurgical techniques, new IOL technologies, and enhancements to IOL power calculations have also positively impacted patients’ refractory status after cataract surgery.

Development and Verification of an Adjustment Factor for Determining the Axial Length Using Optical Biometry in Silicone Oil-Filled Eyes

The aim of this prospective clinical study was to establish and verify an adaptation for axial length (AL) measurement in silicone oil (SO)-filled pseudophakic eyes with a Scheimpflug and partial coherence interferometry (PCI)-based biometer. The AL was measured with a Pentacam AXL (OCULUS Optikgeräte GmbH, Wetzler, Germany) and IOLMaster 700 (Carl Zeiss Meditec, Jena, Germany). The coefficients of variation (CoV) and the mean systematic difference (95% confidence interval (CI)) between the devices were calculated. After implementing a setting for measuring AL in tamponaded eyes with a Pentacam based on data of 29 eyes, another 12 eyes were examined for verification. The mean AL obtained with the Pentacam was 25.53 ± 1.94 mm (range: 21.70 to 30.76 mm), and with IOLMaster, 24.73 ± 1.97 mm (ranged 20.84 to 29.92 mm), resulting in a mean offset of 0.80 ± 0.08 mm (95% CI: 0.77, 0.83 mm), p < 0.001. The AL values of both devices showed a strong linear correlation (r = 0.999). Verification data confirmed good agreement, with a statistically and clinically non-significant mean difference of 0.02 ± 0.04 (95% CI: −0.01, 0.05) mm, p = 0.134. We implemented a specific adaptation for obtaining reliable AL values in SO-filled eyes with the Pentacam AXL.

Agreement of predicted intraocular lens power using swept-source optical coherence tomography and partial coherence interferometry

PURPOSE

To analyze the agreement of the predicted intraocular lens (IOL) power obtained with ANTERION, IOLMaster 700 and Pentacam AXL biometers.

METHODS

We calculated the monofocal and trifocal IOL power using the SRK/T, Haigis, Barrett Universal II and Hoffer Q formulas for 106 eyes. IOL power agreement between devices was evaluated using the Bland-Altman method.

RESULTS

We found significant differences between biometers comparisons (p < 0.001). ANTERION and IOLMaster 700 did not produce significant IOL power differences (p > 0.05), with the same outcomes for medium- and long-eyes. No significant differences were found using the SRK/T, Haigis, or Hoffer Q formulas for short-eyes (p > 0.1). However, Barrett Universal II formula produced significant differences (p < 0.05) and these differences lay between the ANTERION and Pentacam AXL. ANTERION versus IOLMaster 700 comparison showed limits of agreement (LoA) varying from 1.1071D in SRK/T monofocal medium-eyes to 1.6828D in Hoffer Q trifocal all-eyes. The largest LoA (about 3.0D) was found for short-eyes when comparing the Pentacam AXL with the other two devices.

CONCLUSIONS

These devices provided statistically significant but clinically insignificant mean differences in predicted IOL power. However, wide LoA values suggest that for specific eyes these outcomes could be clinically significant.

A comparison of different methods to calculate the axial length measured by optical biometry

ABSTRACT

PurposeTo compare axial length (AL) measurements in long eyes by two swept-source optical coherence tomography (SS-OCT) biometers, one based on the group refractive index (IOLMaster 700, Zeiss) and the other based on sum of segments (Argos, Movu), and compare these measurements to previously published methods to optimize AL.SettingI.R.C.C.S. - G.B. Bietti Foundation, Rome, ItalyDesignProspective case seriesMethodsAL was measured with both optical biometers in myopic patients (AL > 24.00 mm) and compared to the values obtained with Wang-Koch adjustment, polynomial equations for the Holladay 1 and 2 formulas and Cooke modified AL (CMAL).ResultsIn 102 eyes of 55 subjects, a statistically significant difference (p<0.0001) was found among the 6 AL values. Post-test revealed that Argos measurements (26.90 ±1.61 mm) were significantly lower compared to those provided by all methods (p <0.001) but CMAL, whereas IOLMaster 700 measurements (27.01 ±1.65) were higher (p <0.001). No difference was found between the two Holladay equations. CMAL values did not reveal any difference compared to those of the Argos, but a proportional bias showed that in longer eyes CMAL provided smaller values (p <0.0001, r = -0.7221). AL overestimation by the IOLMaster 700 AL compared to the Argos was higher the longer the eye was (p <0.0001, r = 0.6959, r2 = 0.4842).ConclusionThe SS-OCT optical biometer based on the group refractive index overestimates AL compared to the device using segmented AL. CMAL provides the measurements closest to those of the device using segmented AL.

Clinical Reliability of IOL Master 700 in Measurement of Pupil Diameter and Corneal Curvature

Purpose: To compare IOL Master 700 with autokeratometer and video pupillometer in measurement of pupil diameter and corneal curvature.Methods: Pupil diameter were measured with IOL Master 700 and video pupilometer, horizontal keratometry and vertical keratometry were measured with IOL Master 700 and autokeratometer in 100 eyes of 50 children. Paired t-test and Pearson's correlation analysis were used to compare the differences among the devices. Agreement between measurement was analyzed using Bland Altman plot and intraclass correlation coefficient.Results: Comparing IOL Master 700 and video pupilometer for pupil diameter, there was no significant difference (p > 0.05). There was also no significant difference between IOL Master 700 and autokeratometer in measurement of vertical keratometry (p > 0.05). However, regarding horizontal keratometry there was significant difference between IOL Master 700 and autokeratometer, horizontal keratometry measured with IOL Master 700 was steeper than with auto keratometer, +0.105 diopters (D) in right eye and +0.130 D in left eye (p < 0.05).Conclusions: There was good agreement between IOL Master 700 and comparator instruments in regards to pupil diameter and corneal curvature. IOL Master 700 can be helpful in uncooperative children for measuring pupil diameter and corneal curvature at the same time.

Agreement between 2 swept-source OCT biometers and a Scheimpflug partial coherence interferometer

PURPOSE

To evaluate the agreement between different parameters obtained with 2 swept-source optical coherence tomography (SS-OCT)-based biometers and 1 Scheimpflug camera with partial coherence interferometry (PCI).

SETTING

Single center, Oftalvist, Alicante, Spain.

DESIGN

Prospective case series.

METHODS

Biometry was performed in 49 eyes using 3 optical biometers: ANTERION SS-OCT, IOLMaster 700 SS-OCT, and Pentacam AXL PCI. Keratometry (K), J0 and J45 vectors, anterior chamber depth (ACD), central corneal thickness (CCT), white-to-white (WTW), lens thickness (LT), and axial length (AL) were measured with each device. Bland-Altman analysis was applied.

RESULTS

This study comprises 49 eyes of 49 patients. There were no statistically significant differences for K1, K2, J0 and J45 between the 3 devices (P > .9). In contrast, there was a statistically significant difference in the ACD, CCT, WTW, LT, and AL between the biometers (P < .001). Specifically, there was a statistically significant difference between ACD, CCT, and WTW values for all-pairwise comparisons. IOLMaster showed the shortest ACD value and ANTERION showed the largest ACD. IOLMaster showed the highest CCT and Pentacam showed the lowest CCT. IOLMaster showed the largest WTW and Pentacam showed the shortest WTW. The LT measured with IOLMaster was thicker than that measured with ANTERION. There was a statistically significant difference in the AL between IOLMaster and Pentacam, with a shorter AL measured with IOLMaster (P < .001), but no differences were found between ANTERION and IOLMaster (P = .599) and between ANTERION and Pentacam (P = .054).

CONCLUSIONS

Mean differences and the limits of agreement obtained in all-pairwise comparisons of the different parameters should be judged clinically to consider the interchangeability of these devices.

Comparison of various intraocular lens formulas using a new high-resolution swept-source optical coherence tomographer

PURPOSE

To compare vergence, artificial intelligence, and combined intraocular lens (IOL) calculation formulas using a new swept-source optical coherence tomographer (SS-OCT) and to analyze their performance based on manifest and estimated refractive outcomes of cataract surgery.

SETTING

Department of Ophthalmology, University of Pécs Medical School, Pécs, Hungary.

DESIGN

Retrospective data analysis.

METHODS

Optical biometry readings of patients who underwent uneventful cataract removal and implantation of a monofocal acrylic IOL were used to predict IOL power with Barrett Universal II (BUII), Haigis, Hoffer Q, Holladay 1, Radial Basis Function (RBF) 2.0, Kane, Ladas Super Formula, and SRK/T. All the implanted IOLs were calculated by using the Haigis formula. The arithmetic prediction error and median and mean absolute refractive errors for all formulas were computed. The percentage of eyes within ±0.25 diopters (D), ±0.50 D, and ±1.0 D of prediction error was calculated.

RESULTS

A total of 95 eyes of 95 patients with a mean age of 68.80 ± 7.57 years were included. There was a statistically significant difference in absolute prediction error across the 8 IOL calculation formulas (P < .0001). Haigis showed the lowest mean absolute error, and it differed significantly from the BUII, Hoffer Q, Holladay 1, Ladas, RBF 2.0, and SRK/T formulas (P < .05). In terms of eyes within ±0.25 D, ±0.50 D, and ±1.0 D of prediction error, the Haigis formula showed the overall best performance.

CONCLUSIONS

The results indicated that a recently developed SS-OCT provided accurate ocular biometry measurements before cataract surgery, and the Haigis formula incorporated in its software enabled precise calculation of IOL refractive power.

Ocular biometry with swept-source optical coherence tomography

This study aimed to summarize the outcomes reported when swept-source optical coherence tomography (SS-OCT) is used for ocular biometry. A literature search was performed to identify publications reporting clinical outcomes of patients measured with commercial SS-OCT. Twenty-nine studies were included in this review. A comprehensive analysis of the available data was performed, focusing on parameters used for intraocular lens (IOL) power calculation in cataract surgery, including keratometry, central corneal thickness, white-to-white distance, anterior chamber depth, lens thickness, axial length, IOL power, and pupil diameter. Different metrics for repeatability, reproducibility, and agreement between devices were analyzed. In general, SS-OCT biometers provide excellent repeatability and reproducibility outcomes; however, the differences obtained for some parameters measured in agreement studies should be carefully analyzed to validate the interchangeability between devices. The good outcomes reported lead us to conclude that optical biometers based on SS-OCT technology are likely to become the gold standard for ocular biometry.

Prediction of cycloplegic refraction for noninvasive screening of children for refractive error

Detection of refractive error in children is crucial to avoid amblyopia and its impact on quality of life. We here performed a retrospective study in order to develop prediction models for spherical and cylinder refraction in children. The enrolled 1221 eyes of 617 children were divided into three groups: the development group (710 eyes of 359 children), the validation group (385 eyes of 194 children), and the comparison group (126 eyes of 64 children). We determined noncycloplegic and cycloplegic refraction values by autorefractometry. In addition, several noncycloplegic parameters were assessed with the use of ocular biometry. On the basis of the information obtained from the development group, we developed prediction models for cycloplegic spherical and cylinder refraction in children with the use of stepwise multiple regression analysis. The prediction formulas were validated by their application to the validation group. The similarity of noncycloplegic and predicted refraction to cycloplegic refraction in individual eyes was evaluated in the comparison group. Application of the developed prediction models for spherical and cylinder refraction to the validation group revealed that predicted refraction was significantly correlated with measured values for cycloplegic spherical refraction (R = 0.961, P < 0.001) or cylinder refraction (R = 0.894, P < 0.001). Comparison of noncycloplegic, cycloplegic, and predicted refraction in the comparison group revealed that cycloplegic spherical refraction did not differ significantly from predicted refraction but was significantly different from noncycloplegic refraction, whereas cycloplegic cylinder refraction did not differ significantly from predicted or noncycloplegic values. Our prediction models based on ocular biometry provide estimates of refraction in children similar to measured cycloplegic spherical and cylinder refraction values without the application of cycloplegic eyedrops.

Comparative Analysis of Swept-Source Optical Coherence Tomography and Partial Coherence Interferometry Biometers in the Prediction of Cataract Surgery Refractive Outcomes

Purpose

To compare the accuracy of pre-operative corneal measurements obtained with four devices, and the refractive outcomes of two optical biometers.

Setting

Private practice.

Design

Retrospective.

Methods

Data taken from biometric measurements on 299 consecutive eyes prior to cataract surgery were retrospectively analyzed using the Argos SS-Optical Biometer and the Lenstar LS900 PCI optical biometer. As part of the standard cataract surgery pre-operative exam, patients also underwent placido disk topography and Scheimpflug tomography. Keratometry, anterior chamber depth, corneal diameter, pupil diameter, central corneal thickness and axial length were all measured. The comparable measurements were compared. Finally, for those eyes where cataract surgery was performed, the post-operative refractive results were compared to the predictive results of the two biometers.

Results

The SS-OCT Argos was able to measure all eyes, while five eyes could not be measured with the Lenstar LS900 PCI. Axial length measurements were performed only with the Argos and Lenstar devices. The eyes that could not be measured by the Lenstar LS900 PCI included dense grade IV nuclear sclerosis and large posterior subcapsular cataracts. In the primary endpoints, there was strong correlation between the Argos and the Lenstar devices in eyes with an axial length between 20 and 30 mm.

Conclusion

The predictive accuracies of the Argos Optical Biometer and Lenstar LS900 PCI are similar, except in medium and long eyes, in which the predictive accuracy of Argos SS-OCT biometry was higher. The Argos system was found easier to use by technicians when compared to the other biometry devices.

Ratio of Axial Length to Corneal Radius in Japanese Patients and Accuracy of Intraocular Lens Power Calculation Based on Biometric Data

PURPOSE

To evaluate the features of the axial length-to-corneal radius (AL/CR) ratio in Japanese patients with cataracts and to determine the accuracy of intraocular lens (IOL) power calculation formulas according to the AL/CR features and the axial length (AL).

DESIGN

Retrospective observational case series.

METHODS

Setting was a clinical practice. Patient population was a total of 1,135 eyes (1,135 patients) with cataracts. Observation procedures included measurement of the AL and corenal radius (CR) by optical biometry and evaluation of the refractive outcomes by using the SRK/T, Holladay 1, Hoffer Q, Haigis, and Barrett Universal II formulas. Main outcome measurements were the features of the AL/CR ratio and the accuracy of IOL power calculations based on the AL/CR ratio and the AL.

RESULTS

The mean AL/CR ratio was 3.15 ± 0.19. Significant weak negative correlations were observed between the spherical equivalent (SE) and AL (r = -0.7489; P < .001) and between the SE and AL/CR ratio (r = -0.8069; P < .001); no correlation was found between the SE and CR (r = 0.0208, P = .483). For medium ALs and high AL/CR ratios, the SRK/T formula performed less accurately. For long ALs and high AL/CR ratios, the Holladay 1 and Hoffer Q formulas performed less accurately. The Barrett Universal II formula performed well across a range of ALs and AL/CR ratios.

CONCLUSIONS

The AL/CR ratio explained the total variation in the SE better than the AL alone. Surgeons should pay attention to the selection of IOL power calculation formulas in eyes with high AL/CR ratios.

Intraocular Lens Power Formulas, Biometry, and Intraoperative Aberrometry: A Review

The refractive outcome of cataract surgery is influenced by the choice of intraocular lens (IOL) power formula and the accuracy of the various devices used to measure the eye (including intraoperative aberrometry [IA]). This review aimed to cover the breadth of literature over the previous 10 years, focusing on 3 main questions: (1) What IOL power formulas currently are available and which is the most accurate? (2) What biometry devices are available, do the measurements they obtain differ from one another, and will this cause a clinically significant change in IOL power selection? and (3) Does IA improve refractive outcomes? A literature review was performed by searching the PubMed database for articles on each of these topics that identified 1313 articles, of which 166 were included in the review. For IOL power formulas, the Kane formula was the most accurate formula over the entire axial length (AL) spectrum and in both the short eye (AL, ≤22.0 mm) and long eye (AL, ≥26.0 mm) subgroups. Other formulas that performed well in the short-eye subgroup were the Olsen (4-factor), Haigis, and Hill-radial basis function (RBF) 1.0. In the long-eye group, the other formulas that performed well included the Barrett Universal II (BUII), Olsen (4-factor), or Holladay 1 with Wang-Koch adjustment. All biometry devices delivered highly reproducible measurements, and most comparative studies showed little difference in the average measures for all the biometric variables between devices. The differences seen resulted in minimal clinically significant effects on IOL power selection. The main difference found between devices was the ability to measure successfully through dense cataracts, with swept-source OCT-based machines performing better than partial coherence interferometry and optical low-coherence reflectometry devices. Intraoperative aberrometry generally improved outcomes for spherical and toric IOLs in eyes both with and without prior refractive surgery when the BUII and Hill-RBF, Barrett toric calculator, or Barrett True-K formulas were not used. When they were used, IA did not result in better outcomes.

Effects on IOL Power Calculation and Expected Clinical Outcomes of Axial Length Measurements Based on Multiple vs Single Refractive Indices

Purpose

To compare axial length measurements based on multiple specific refractive indices for each segment of the eye to those obtained using a single refractive index for the entire eye and to evaluate the subsequent effects on IOL power calculation.

Setting

One site in Lynwood, CA.

Design

Single-arm, non-interventional, non-randomized retrospective chart review.

Methods

Eyes undergoing cataract surgery where biometry and IOL power calculations were based on axial length calculated with multiple specific refractive indices (multiple) were evaluated. A simulated axial length based on using a single refractive index was calculated for each case (single). The expected residual refractions based on different IOL formulas were calculated for both single and multiple groups. Formulas were then optimized, and the mean prediction errors (MPE) and mean absolute prediction errors (MAE) were calculated, based on the difference between the (optimized) expected value and the actual refractive outcome.

Results

A total of 595 eligible eyes were evaluated. Differences between the axial lengths determined in the single and multiple groups ranged from +0.28 mm to −0.14 mm, with a significant correlation between the difference in AL and average AL (r² = 0.73, p < 0.001). AL differences between groups were statistically significant in long and short eyes (p < 0.001) but not in average eyes or overall (p > 0.25). In nearly all cases, the average MPE in the multiple group was lower than that for the single group across all axial lengths and formulas. When larger differences in MAE were present, the multiple group results were more often lower (better).

Conclusion

Differences were found between axial lengths calculated using a single refractive index and multiple refractive indices, mainly in the short and long eyes. Differences had some effect on IOL power calculation. Such effects may become increasingly important as the precision of formulas increases.

Comparison of composite and segmental methods for acquiring optical axial length with swept-source optical coherence tomography

This study compared the optical axial length (AL) obtained by composite and segmental methods using swept-source optical coherence tomography (SS-OCT) devices, and demonstrated its effects on the post-operative refractive errors (RE) one month after cataract surgery. Conventional AL measured with the composite method used the mean refractive index. The segmented-AL method used individual refractive indices for each ocular medium. The composite AL (24.52 ± 2.03 mm) was significantly longer (P < 0.001) than the segmented AL (24.49 ± 1.97 mm) among a total of 374 eyes of 374 patients. Bland–Altman analysis revealed a negative proportional bias for the differences between composite and segmented ALs. Although there was no significant difference in the RE obtained by the composite and segmental methods (0.42 ± 0.38 D vs 0.41 ± 0.36 D, respectively, P = 0.35), subgroup analysis of extremely long eyes implanted with a low power intraocular lens indicated that predicted RE was significantly smaller with the segmental method (0.45 ± 0.86 D) than that with the composite method (0.80 ± 0.86 D, P < 0.001). Segmented AL with SS-OCT is more accurate than composite AL in eyes with extremely long AL and can improve post-operative hyperopic shifts in such eyes.

Accuracy of the Hill-radial basis function method and the Barrett Universal II formula

PURPOSE

The aim was to assess the postoperative results of a biometric method using artificial intelligence (Hill-radial basis function 2.0), and data from a modern formula (Barrett Universal II) and the Sanders-Retzlaff-Kraft/Theoretical formula.

METHODS

Phacoemulsification and biconvex intraocular lens implantation were performed in 186 cataractous eyes. The diopters of intraocular lens were established with the Hill-radial basis function method, based on biometric data obtained using the Aladdin device. The required diopters of the intraocular lens were also calculated by the Barrett Universal II formula and with the Sanders-Retzlaff-Kraft/Theoretical formula. The differences between the manifest postoperative refractive errors and the planned refractive errors were calculated, as well as the percentage of eyes within ±0.5 D of the prediction error. The mean- and the median absolute refractive errors were also determined.

RESULTS

The mean age of the patients was 70.13 years (SD = 10.67 years), and the mean axial length was 23.47 mm (range = 20.72-28.78 mm). The percentage of eyes within a prediction error of ±0.5 D was 83.62% using the Hill-radial basis function method, 79.66% with the Barrett Universal II formula, and 74.01% in the case of the Sanders-Retzlaff-Kraft/Theoretical formula. The mean- and the median absolute refractive errors were not statistically different.

CONCLUSION

Clinical success was the highest when using the biometric method, based on pattern recognition. The results obtained using Barrett Universal II came a close second. Both methods performed better compared to a traditionally used formula.