Update on Intraocular Lens Power Calculation Study Protocols: The Better Way to Design and Report Clinical Trials.

It was almost 40 years ago when one of the authors (K.J.H.) published an organized system to quantify the accuracy of intraocular lens (IOL) power calculation formulas, methods, and instruments. At the behest of the editor of the American Journal of Ophthalmology, the IOL Power Club (along with a statistician) published an editorial in 2015 modernizing and quantifying the proper protocols for these studies. Over the past decade, so many new optical biometers, formulas, and methods (whose accuracies have yet to be completely tested) have been introduced that we were asked to modernize and update these guidelines yet again to help others design and report correctly the results of clinical studies on IOL power calculation and biometry for 2020. We evaluated guidelines to enroll patients, including visual acuity minimums, exclusion of bilateral eyes, sample size issues, demographics (age, gender, and ethnicity), and whether such studies should not be performed using the same data that were used to develop the formula being tested. We showed the absolute need for constant optimization, which formulas should be tested for comparison, refraction measurement (testing distance), as well as the analysis of the prediction error (median and mean absolute errors; standard deviation; range of errors; percentage of eyes with a prediction within ±0.25 diopter [D], ±0.50 D, ±0.75 D, and ±1.00 D; and interquartile displays) and statistical methods of analyses. We present methods of ranking formula accuracy, including the new Haigis IOL Formula Performance Index. We also point out the issues of who programmed the formulas being tested, that all formulas used in the study must be referenced, and the software version number of all instruments used in the study should be stated clearly. The definition of anterior chamber depth should be stated as measured from the corneal epithelium to the lens. We hope that these recommendations will help researchers to improve the validity and accuracy of their studies with the ultimate goal to improve the accuracy of IOL power calculation.

Intraoperative refractive biometry for predicting intraocular lens power calculation after prior myopic refractive surgery.

PURPOSE: To evaluate a new method of intraoperative refractive biometry (IRB) for intraocular lens (IOL) power calculation in eyes undergoing cataract surgery after prior myopic LASIK or photorefractive keratectomy. DESIGN: Retrospective consecutive cases series. PARTICIPANTS: We included 215 patients undergoing cataract surgery with a history of myopic LASIK or photorefractive keratectomy. METHODS: Patients underwent IRB for IOL power estimation. The Optiwave Refractive Analysis (ORA) System wavefront aberrometer was used to obtain aphakic refractive measurements intraoperatively and then calculate the IOL power with a modified vergence formula obtained before refractive surgery. Comparative effectiveness analysis was done for IRB predictive accuracy of IOL power determination against 3 conventional clinical practice methods: surgeon best preoperative choice (determined by the surgeon using all available clinical data), the Haigis L, and the Shammas IOL formulas. MAIN OUTCOME MEASURES: Median absolute error of prediction and percentage of eyes within ±0.50 diopters (D) and ±1.00 D of refractive prediction error. RESULTS: In 246 eyes (215 first eyes and 31 second eyes) IRB using ORA achieved the greatest predictive accuracy (P < 0.0001), with a median absolute error of 0.35 D and mean absolute error of 0.42 D. Sixty-seven percent of eyes were within ±0.5 D and 94% were within ±1.0 D of the IRB's predicted outcome. This was significantly more accurate than the other preoperative methods: Median absolute error was 0.6, 0.53, and 0.51 D for surgeon best choice, Haigis L method, and Shammas method, respectively. CONCLUSIONS: The IOL power estimation in challenging eyes with prior LASIK/photorefractive keratectomy was most accurately predicted by IRB/ORA.

Meridional analysis for calculation of the toric power of phakic IOLs.

PURPOSE: To present a reproducible method to calculate the toricity needed at the intraocular lens (IOL) plane with toric phakic IOLs (ICL, Staar Surgical) and compare its results with those obtained with the online calculator provided by the manufacturer. DESIGN: Retrospective case series. SETTING: Private practice, Buenos Aires, Argentina. METHODS: The formula originally described by Holladay to calculate the IOL power in phakic eyes was used to calculate the required spherical power along the less refractive meridian and along the more refractive meridian. Meridional analysis was applied to calculate the required toricity at the IOL plane and the surgically induced corneal astigmatism was incorporated into the calculations. The refractive cylinder predicted by this method and by the online calculator of the manufacturer were compared to the postoperative refractive cylinder by means of vector analysis. The possible changes in the ratio of toricity in patients with different amounts of astigmatism and anterior chamber depth are assessed in a theoretical section. RESULTS: In 35 eyes, the measured mean postoperative refractive cylinder was 0.09 D @ 99°, the mean predicted postoperative refractive astigmatism was 0.04 D @ 102° according to the manufacturer's online calculator and 0.09 D @100° according to our method. With both methods, 91.43% of eyes had an absolute cylinder prediction error within ±0.50 diopters. CONCLUSIONS: The method described in this article to calculate the toricity of phakic IOLs has a refractive accuracy similar to that of the original calculator developed by the manufacturer.

Spherical Equivalent Prediction Analysis in IOL Power Calculations Using Eyetemis, A Comprehensive Approach.

PURPOSE: To compare two different datasets, using Eyetemis, an online analytical tool designed for assessing the spherical equivalent prediction errors (SEQ-PE) of intraocular lens (IOL) power calculation formulas following cataract surgery. SETTING: Institutional. DESIGN: Retrospective case series. METHODS: The study was comprised of two distinct datasets of patients who had undergone successful cataract surgery. Dataset-1 includes standard eyes whereas Dataset-2 includes eyes with keratoconus. An online tool was used for SEQ-PE analysis across the 2 datasets, adhering to ISO standards for evaluating accuracy based upon trueness and precision. The tool incorporates robust t-tests for comparing the trimmed-mean of the data, adjusting for heteroscedasticity. IOL constants in Dataset-1 were optimized for the comparison of Hoffer Q, Holladay1, SRK/T, Haigis and Barrett Universal II (BUII) formulas. In Dataset-2, IOL constants from the IOLCon website, were used for the comparison of the BUII and its designated KCN-version: Barrett TrueK Keratoconus (TrueK [KCN]). RESULTS: For Dataset-1: the trimmed-mean SEQ-PE values of all formulas were not significantly different from zero. BUII had superior precision and accuracy compared to all other formulas except from Haigis (P≤ 0.04). For Dataset-2: BUII's trimmed-mean SEQ-PE was significantly different from zero (0.59D, P< 0.01), unlike the TrueK [KCN] (0.12D, P= 0.10). Additionally, TrueK [KCN] exhibited enhanced precision and accuracy relative to BUII (P< 0.01). CONCLUSIONS: The online analysis tool provides a streamlined approach for assessing the prediction accuracy of SEQ refraction following cataract surgery, effectively evaluating trueness, precision, and overall accuracy through the use of advanced statistical methods.

Comparison of Keratometry and Total Corneal Power, as measured by a swept-source OCT-based optical biometer, for IOL power calculation in Asian eyes.

PURPOSE: To investigate whether standard keratometry (K) or total corneal power (TCP) lead to more accurate refractive outcomes for intraocular lens (IOL) power calculation. SETTING: Public hospital. DESIGN: Retrospective evaluation of a diagnostic test instrument. METHODS: Preoperatively all patients underwent optical biometry with the Anterion (Heidelberg), a swept-source optical coherence tomographer providing both K and TCP. The same IOL model was implanted in all cases. The whole sample was divided into a training dataset, used to optimize the formula constants, and a testing dataset, used to investigate the spherical equivalent prediction error (SEQ-PE) of 8 IOL power formulas. Trueness, precision and accuracy were evaluated by means of the robust two-sample t-test. Cochran's Q test was performed to assess whether the percentage of eyes with an SEQ-PE within each threshold was significantly different; in such an event, the McNemar test was then applied. RESULTS: Both the training and testing datasets included 317 eyes. No significant differences were detected for trueness, due to constant optimization. Precision and accuracy were better when K was entered, although a statistically significant difference was observed only with the EVO (precision: p = 0.02 and accuracy: p = 0.03) and Haigis formula (p <0.01 for both precision and accuracy). No significant differences were observed for the percentage of eyes with an absolute SEQ-PE within any threshold. CONCLUSIONS: With most formulas, IOL power calculation is not more accurate when TCP is used instead of K.

Differences Between Simulated Keratometry and Total Corneal Power in Eyes With Keratoconus and a Formula to Improve IOL Power Calculation Results.

PURPOSE: To compare simulated keratometry (SimK) and total corneal power (TCP) in keratoconic eyes, to determine whether the differences are systematic and predictable and to evaluate an adjusted TCP-based formula for intraocular lens (IOL) power calculation. METHODS: In a consecutive series of keratoconic eyes, measurements of SimK, TCP, posterior keratometry, and anterior and posterior corneal asphericities (Q-values) were retrospectively collected. The difference between SimK and TCP was linearly correlated to the biometric parameters. In a separate sample of keratoconic eyes that had undergone cataract surgery, IOL power was calculated with the Barrett Universal II, Hoffer QST, Holladay 1, Kane, and SRK/T formulas using the SimK and an adjusted TCP power. The respective prediction errors were calculated. RESULTS: A total of 382 keratoconic eyes (271 patients) were enrolled. An increasing overestimation of SimK by TCP was detected from stage I to III, with a significant correlation between the SimK and TCP difference and SimK in the whole sample (P < .0001, r2 = 0.1322). Approximately 7% of cases presented an underestimation of SimK by TCP. IOL power calculation with the adjusted TCP improved outcomes, achieving a maximum of 80% of eyes with a prediction error within ±0.50 diopters with the Hoffer QST, Holladay 1, and Kane formulas. CONCLUSIONS: Overall, SimK overestimated TCP. Such a difference could not be predicted by any variable. The proposed TCP-adjustment formula (TCPadj = TCP + 0.56 diopters) in keratoconic eyes for IOL power calculation might be valuable for improving refractive outcomes. [J Refract Surg. 2024;40(4):e253-e259.].

Differences Between Keratometry and Total Keratometry Measurements in a Large Dataset Obtained With a Modern Swept Source Optical Coherence Tomography Biometer.

PURPOSE: This study aimed to explore the concept of total keratometry (TK) by analyzing extensive international datasets representing diverse ethnic backgrounds. The primary objective was to quantify the disparities between traditional keratometry (K) and TK values in normal eyes and assess their impact on intraocular lens (IOL) power calculations using various formulas. DESIGN: Retrospective multicenter intra-instrument reliability analysis. METHODS: The study involved the analysis of biometry data collected from ten international centers across Europe, the United States, and Asia. Corneal power was expressed as equivalent power and astigmatic vector components for both K and TK values. The study assessed the influence of these differences on IOL power calculations using different formulas. The results were analyzed and plotted using Bland-Altman and double angle plots. RESULTS: The study encompassed a total of 116,982 measurements from 57,862 right eyes and 59,120 left eyes. The analysis revealed a high level of agreement between K and TK values, with 93.98% of eyes exhibiting an absolute difference of 0.25 D or less. Astigmatism vector differences exceeding 0.25 D and 0.50 D were observed in 39.43% and 1.08% of eyes, respectively. CONCLUSIONS: This large-scale study underscores the similarity between mean K and TK values in healthy eyes, with rare clinical implications for IOL power calculation. Noteworthy differences were observed in astigmatism values between K and TK. Future investigations should delve into the practicality of TK values for astigmatism correction and their implications for surgical outcomes.

Anterior chamber and aqueous depth measurement in pseudophakic eyes: agreement between ultrasound biometry and scheimpflug imaging.

PURPOSE: To compare anterior chamber depth (ACD) and aqueous depth (AQD) measurements provided by a Scheimpflug camera combined with corneal topography to those obtained by immersion ultrasound (US) biometry when assessing the distance between the cornea and intraocular lens (IOL) in pseudophakic patients. METHODS: In a sample of 40 consecutive patients, each patient underwent measurements of ACD and AQD by means of the two techniques. Scheimpflug (Sirius; C.S.O., Firenze, Italy) measurements were obtained by manually tracing a line between the anterior surface of the IOL and the central cornea. Results were compared by t test. Agreement was evaluated by Bland-Altman plots with 95% limits of agreement (LoA). RESULTS: There was no statistically significant difference between the AQD as measured by US (3.95 ± 0.34 mm; range: 3.39 to 4.74 mm) and the AQD as measured by Scheimpflug photography (3.96 ± 0.34 mm; range: 3.41 to 4.77 mm; P = .3187). The statistically (but not clinically) significant difference between the ACD as measured by US (4.54 ± 0.37 mm; range: 3.93 to 5.35 mm) and Scheimpflug photography (4.58 ± 0.34 mm; range: 4.03 to 5.36 mm; P = .0024) disappeared after setting the US speed for ACD at 1,545 m/sec (mean ACD: 4.58 ± 0.37 mm; range: 3.96 to 5.39 mm). The 95% LoA ranged between -0.15 and +0.18 mm for AQD and between -0.12 and +0.21 mm for ACD. CONCLUSIONS: In pseudophakic eyes, the manual ACD and AQD measurements obtained from the Scheimpflug camera combined with corneal topography are not significantly different compared to those provided by US and therefore can be considered interchangeable with the latter.

A new slant on toric intraocular lens power calculation.

PURPOSE: The AcrySof Toric intraocular lens (IOL) (Alcon Laboratories, Inc., Fort Worth, TX) is designed to correct corneal astigmatism ranging from 0.67 to 4.11 diopters (D). The authors reviewed the clinical outcomes of this IOL and investigated possible improvements of the online calculator provided by the manufacturer. METHODS: Review of published studies. RESULTS: The AcrySof Toric IOL can provide good results, although a mean overcorrection or undercorrection relative to the intended correction has been found by some authors. Stability over time has been reported to be excellent. Rotation occurs mainly in the first postoperative month and is greater in eyes with a longer axial length due to the larger capsule size. The online calculator of this IOL may be improved by considering the posterior corneal astigmatism and better calculating the conversion of the IOL cylinder from the IOL plane to the corneal plane, which may be inaccurate for two reasons. First, given the variable distance between the IOL and the cornea in short and long eyes, the fixed ratio (1.46) provided by the manufacturer cannot be used to calculate this conversion. Second, the online calculator does not take into account the effect of varying IOL sphere power. CONCLUSION: The AcrySof Toric IOL is a reliable choice to correct corneal astigmatism at the time of cataract surgery. Results will be improved once the online calculator by the manufacturer considers the posterior corneal astigmatism and the variable ratio between the toricity at the IOL and corneal plane.

Comparison of the new Hoffer QST with 4 modern accurate formulas.

PURPOSE: To investigate the new Hoffer QST (Savini/Taroni) formula (HQST) and compare it with the original Hoffer Q (HQ) and 4 latest generation formulas. SETTING: I.R.C.C.S.-G.B. Bietti Foundation, Rome, Italy. DESIGN: Retrospective case series. METHODS: Refractive outcomes of the HQST, Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO) 2.0, HQ, Kane, and Radial Basis Function (RBF) 3.0 formulas were compared. Subgroup analysis was performed in short (<22 mm) and long (>25 mm) axial length eyes. The SD of the prediction error (PE) was investigated using the heteroscedastic method. RESULTS: 1259 eyes of 1259 patients divided in a White group (n=696), implanted with the AcriSof SN60AT (Alcon Labs), and an Asian group (n=563), implanted with the SN60WF (Alcon Labs), were investigated. In the Asian group, the heteroscedastic method did not disclose any significant difference among the SD of the 4 modern formulas (range from 0.333 to 0.346 D), whereas the SD of the HQ formula (0.384 D) was significantly higher. Compared with the original HQ formula, in both White and Asian groups, the HQST formula avoided the mean myopic PE in short eyes and the mean hyperopic PE in long eyes. CONCLUSIONS: The new HQST formula was superior to the original HQ formula and reached statistical and clinical results comparable with those achieved by the BUII, EVO, Kane, and RBF formulas.

Optical Biometry and IOL Calculation in a Commercially Available Optical Coherence Tomography Device and Comparison With Pentacam AXL.

PURPOSE: Optical devices are the gold standard for ocular biometry; however, they are unable to obtain high-quality optical coherence tomography (OCT) images. The current study aimed to evaluate ocular measurements and intraocular lens (IOL) calculation used in an anterior/posterior segment OCT device and to compare the results with those of a validated biometer. DESIGN: Prospective evaluation of a diagnostic tool. METHODS: This study enrolled healthy subjects at the Hygeia Clinic, Gdansk, Poland, between October 2021 and November 2021. All individuals had ocular biometry measured with a validated biometer (Pentacam AXL) and with a new module of an anterior/posterior segment OCT device (Revo 80, Optopol Technologies). All IOL calculations were performed for the right eye with keratometric values from the Pentacam for one IOL: the Alcon AcrySof IQ SN60WF, with plano target setting. RESULTS: The mean age of the 144 participants was 25.23 ± 7.15 years. The axial length measured with Revo was longer than with Pentacam AXL (24.08 ± 1.13 vs 23.98 ± 1.13; P < .0001), a 0.10 ± 0.04 mm difference. This translated into a significantly lower IOL power to achieve emmetropia for all formulas (-0.34 ± 0.15, -0.32 ± 0.13, -0.34 ± 0.19, and -0.30 ± 0.15 for the Hoffer Q, Holladay I, Haigis, and SRK/T formulas, respectively). The study showed high agreement between the devices: nearly 90% of eyes were within ±0.50 diopters for all of the analyzed formulas (r > 0.99). CONCLUSIONS: The present study demonstrates that the results of IOL calculation with the OCT biometer have a very strong correlation with those obtained with the Pentacam AXL; however, axial length measurements and calculated IOL power cannot be considered interchangeable.

Repeatability of new optical biometer and agreement with 2 validated optical biometers, all based on SS-OCT.

PURPOSE: To evaluate the repeatability of the measurements provided by a new optical biometer (EyeStar 900) based on swept-source optical coherence tomography (SS-OCT) and their agreement with the measurements given by 2 validated biometers based on the same technology, the IOLMaster 700 and Argos. SETTING: IRCCS G.B. Bietti Foundation, Rome, Italy. DESIGN: Prospective evaluation of diagnostic test. METHODS: In a series of unoperated eyes, 3 consecutive scans were acquired with the EyeStar 900, and 1 with the IOLMaster 700 and the Argos. The following biometry parameters were analyzed: axial length (AL), keratometry (K), corneal astigmatism, central corneal thickness, corneal diameter (CD), anterior chamber depth (ACD), lens thickness (LT), and lens tilting. Repeatability was assessed using test-retest variability, the coefficient of variation (CoV), and the intraclass correlation coefficient (ICC); agreement was based on the 95% limits of agreement. RESULTS: 56 eyes of 56 patients were analyzed. High repeatability was achieved for all measured parameters, as the CoV was <1% in most cases and ICC was >0.95 for all parameters. Good to high agreement was found among the measurements of the 3 optical biometers, although some statistically significant differences were detected between the EyeStar 900 and Argos (mean K, ACD, LT, and CD were higher with the Argos). The Argos measured a shorter AL in eyes >25 mm. CONCLUSIONS: The new generation SS-OCT EyeStar 900 optical biometer produces highly repeatable measurements that are in good agreement with those provided by 2 previously validated instruments.

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.].

Accuracy of Nine Formulas to Calculate the Powers of an Extended Depth-of-Focus IOL Using Two SS-OCT Biometers.

PURPOSE: To evaluate the accuracy of nine formulas to calculate the power of a new extended depth-of-focus intraocular lens (EDOF IOL), the AcrySof IQ Vivity (Alcon Laboratories, Inc), using measurements from two optical biometers, the IOLMaster 700 (Carl Zeiss Meditec AG) and Anterion (Heidelberg Engineering GmbH). METHODS: After constant optimization, the accuracy of these formulas was analyzed in 101 eyes: Barrett Universal II, EVO 2.0, Haigis, Hoffer Q, Holladay 1, Kane, Olsen, RBF 3.0, and SRK/T. Both standard and total keratometry from the IOLMaster 700 and standard keratometry from the Anterion were used for each formula. RESULTS: Constant optimization provided slightly different values for the A-constant, which ranged between 118.99 and 119.16, depending on the formula and the optical biometer. According to the heteroscedastic test, within each keratometry modality the standard deviation of the SRK/T was significantly higher compared to that of the Holladay 1, Kane, Olsen, and RBF 3.0 formulas. The SRK/T formula provided less accurate results also when the absolute prediction errors were compared by Friedman test. According to McNemar's test with Holm corrections, statistically significant differences were found within each keratometry modality between the percentage of eyes with a prediction error within ±0.25 diopters obtained with the Olsen formula compared to the Holladay 1 and Hoffer Q formulas. CONCLUSIONS: Constant optimization remains a mandatory step to achieve the best outcomes with the new EDOF IOL: the same constant should not be used for all formulas and for both optical biometers. Different statistical tests revealed that older IOL formulas have lower accuracy compared to newer formulas. [J Refract Surg. 2023;39(3):158-164.].

Scheimpflug camera measurement of anterior and posterior corneal curvature in eyes with previous radial keratotomy.

PURPOSE: To compare the anterior and posterior corneal curvature in eyes with previous radial keratotomy (RK) to normal unoperated eyes. METHODS: In this retrospective observational case series, 29 eyes from 29 consecutive patients were analyzed and compared to a control group of 71 unoperated eyes. Corneal imaging was obtained by a rotating Scheimpflug camera (Pentacam, Oculus Optikgeräte GmbH). Anterior and posterior corneal curvature radii were measured at the 3-mm zone. RESULTS: The mean anterior and posterior corneal radii were 9.54 ± 0.89 and 8.54 ± 1.01 mm, respectively, both values being significantly higher than in the control group (7.81 ± 0.28 and 6.40 ± 0.24 mm, respectively, P<.0001). The mean anterior-to-posterior corneal curvature ratio was 1.12 ± 0.07, a value significantly lower than in the control group (1.22 ± 0.03, P<.0001). Mean corneal flattening was more evident in the posterior (33.44%) than in the anterior (22.15%) corneal curvature. The mean keratometric index, as calculated with the Gullstrand equation for thick lenses, was 1.3319 ± 0.0026, a value significantly higher than in the control group (1.3281 ± 0.0011, P<.0001). Linear regression detected a significant and directly proportional relationship between the number of radial incisions and flattening of both corneal surfaces (P<.0001). CONCLUSIONS: After RK, both corneal surfaces flatten but do not deform in parallel as commonly accepted, as shown by the fact that the anterior-to-posterior corneal curvature ratio decreases. This finding invalidates the standard keratometric index and thus has relevant implications for intraocular lens power calculation in RK eyes.

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.

Corneal diameter measurements by 3 optical biometers and their effect on phakic intraocular lens sizing.

PURPOSE: To compare phakic intraocular lens size calculations based on corneal diameter (CD) measurements by 3 instruments. SETTING: G.B. Bietti Foundation I.R.C.C.S., Rome, Italy. DESIGN: Retrospective interventional case series. METHODS: Preoperatively, CD was measured with the Aladdin, IOLMaster 700, and Pentacam AXL Wave. The simulated ICL size was computed by entering CD measurements into the manufacturer's calculator. Postoperatively, vaulting was measured by anterior segment optical coherence tomography. The optimal ICL size (OIS) was calculated and compared with the commercially available OIS (CAOIS). RESULTS: 54 eyes (29 patients) with the implantable collamer lens (ICL) were enrolled. The mean CD was 12.02 ± 0.36 mm with the Aladdin, 12.35 ± 0.39 mm with the IOLMaster 700, and 12.22 ± 0.41 mm with the Pentacam AXL Wave ( P &lt; .0001), with the closest agreement between the Pentacam AXL Wave and IOLMaster 700 (95% limits of agreement: -0.43 to +0.17 mm). Vaulting (mean: 558 ± 261 µm) was within 251 and 1000 µm in 49 eyes (83.3%). The mean difference between the simulated ICL size and OIS ranged between -0.11 ± 0.35 mm and 0.10 ± 0.30 mm ( P &lt; .0001), with no statistically significant difference between the IOLMaster 700 and Pentacam AXL Wave. The simulated ICL size was equal to CAOIS in 38 eyes (70.37%) with the Aladdin, 37 eyes (68.52%) with the IOLMaster 700, and 39 eyes (72.22%) with the Pentacam AXL Wave, without any statistically significant difference. CONCLUSIONS: CD measurements by the 3 devices lead to similar percentages of eyes with an ICL size equal to the OIS. Agreement is closer between the IOLMaster 700 and Pentacam AXL Wave.