White-to-white Measurements Research Articles

Repeatability and reproducibility of a new spectral-domain optical coherence tomography biometer and agreement with swept-source optical coherence tomography based biometer.

To assess the repeatability and reproducibility of the Colombo IOL biometer (Moptim, China), which utilizes spectral-domain optical coherence tomography (SD-OCT), in measuring ocular parameters of normal subjects and to compare its agreement with the swept-source optical coherence tomography (SS-OCT)-based IOLMaster 700 biometer (Carl Zeiss Meditec AG, Germany). This prospective study included 91 eyes from 91 normal subjects. The evaluated parameters were axial length (AL), central corneal thickness (CCT), aqueous depth (AQD), anterior chamber depth (ACD), lens thickness (LT), flattest and steepest meridian keratometry (Kf and Ks), mean keratometry (Km), astigmatism (AST) magnitude, white-to-white (WTW) distance, and pupil diameter (PD). The within-subject standard deviation (Sw), test-retest repeatability (TRT), coefficient of variation (CoV), and intraclass correlation coefficient (ICC) were calculated to determine the repeatability and reproducibility. Paired t-tests and Bland-Altman plots with 95% limits of agreement (LoA) were employed to assess the agreement. With respect to intraobserver repeatability, the Sw and TRT values of all evaluated parameters were low. Except J45 and PD, the ICCs were all higher than 0.928. The reproducibility Sw and TRT values of Colombo IOL were also low, and ICCs were not lower than 0.900. Comparing Colombo IOL and IOLMaster 700, the 95% LoA of AL, CCT, AQD, ACD, LT, Kf, Ks, Km, AST, J0, J45, WTW and PD ranged from - 0.08 to 0.03mm, - 21.58 to 5.09μm, 0.01 to 0.15mm, - 0.01 to 0.14mm, - 0.05 to 0.10mm, - 0.14 to 0.59 D, - 0.31 to 0.40 D, - 0.13 to 0.40 D, - 0.68 to 0.32 D, - 0.09 to 0.34 D, - 0.07 to 0.25 D, 0.11 to 1.47mm, and - 0.97 to 2.31mm, respectively. The new SD-OCT-based Colombo IOL biometer demonstrates excellent repeatability and reproducibility. Moreover, it generally agrees well with the SS-OCT-based IOLMaster 700, except for the WTW and PD measurements.

Assessment of measurement variability across automated biometry devices.

To evaluate measurement variability between different readily available automated biometric devices for the purposes of improving surgeon decision making for phakic intraocular lens (IOL) sizing. Private practice (Houston, TX, USA). Prospective, single center, bilateral, non-randomized, open-label, observational study. This study included healthy eyes, with no prior eye surgery, and with a spherical equivalent of at least -1.00D. Orbscan II was compared to Argos, Atlas 9000, caliper, IOLMaster 500, IOLMaster 700, iTrace, Lenstar LS900, Pentacam HR, and Pentacam AXL Wave. Preoperative measurements included white to white (WTW), anterior chamber depth (ACD), and central corneal thickness (CCT). Linear mixed effect models were created to determine adjustment factor between the Orbscan II and other devices for WTW, ACD, and CCT measurements. A total of 204 subjects (408 eyes) completed the study. All mean WTW measurements were significantly different compared to the Orbscan II (p < 0.01), except for Pentacam AXL Wave. All mean ACD and CCT measurements were significantly different compared to the Orbscan II (p < 0.01). Adjustment factors for WTW ranged from -0.65 mm to 0.24 mm. Adjustment factors for ACD ranged from -0.21 mm to -0.16 mm. Adjustment factors for CCT ranged from 19.9 µm to -36.0 µm. The biometers tested were not interchangeable with the Orbscan II. Adjustment factors for WTW and ACD may compensate for differences between devices and adapt ICL sizing recommendations.

Behavior of biometric parameters during clinical hours

Purpose: To evaluate and quantify variation of biometric parameters - axial length (AL), anterior chamber depth (ACD), central corneal thickness (CCT) and white-to-white (WTW).Methods: A population-based retrospective cohort study was performed on patients who underwent a biometry test prior to cataract surgery using the IOL Master 700 (Carl Zeiss Meditec, Jena, Germany) between the years 2017-2021. Differences in these parameters were evaluated between scans executed at different times of the day.Results: 21,975 examinations of 8,611 patients were included. Mean age was 70.50±12.56 years. The mean time of the biometry exams was 10:52±1:23 AM. Measurements of AL, ACD, CCT and WTW were tested hourly and grouped between 7:00-9:00 AM and 12:00-03:00 PM.All the parameters showed a diurnal increase with a significance of p<0.001 (AL from 23.64±1.5 to 24.01±1.76mm; ACD from 3.29±0.67 to 3.35± 0.64mm; CCT from 0.52±0.04 to 0.53±0.04 µm and WTW from11.83±0.46 to 11.90±0.51mm). The most significant change was seen in AL.The difference between time groups remained significant in a generalized linear mixed model (P<0.001).Conclusions: There are fluctuations in AL, ACD, CCT, WTW measurements during office hours. These results raise questions about the significance of timing of the biometry exam and the effect on the ELP calculation.

A comparison of white-to-white measurements obtained by Anterion AS-OCT versus three optical devices in refractive surgery candidates.

To assess the agreement between Anterion AS-OCT and three optical devices in measuring the white-to-white (WTW) diameter in candidates for refractive surgery. In this cross-sectional prospective study, 129 right eyes of 129 normal individuals underwent consecutive scans with the Anterion, the Pentacam AXL, the IOLMaster 700, and the Orbscan IIz. Mean difference (MD), 95% limits of agreement (LoA), and concordance correlation coefficient (CCC) were calculated to assess agreement and interchangeability. The mean age of participants was 30.4 ± 5.9 (range: 21-47) years. The mean WTW distance measured by the different instruments was as follows: 12.00 ± 0.42 mm (range, 10.57 to 13.05) using the Anterion, 11.87 ± 0.34 (11.10 to 12.80) using the Pentacam, 12.12 ± 0.44 (11.00 to 13.30) using the IOLMaster, and 11.73 ± 0.37 (11.00 to 13.10) using the Orbscan. The MD and 95% LoA for Anterion vs. Pentacam, IOLMaster, or Orbscan were [0.11; -0.31 to 0.54 mm], [-0.13; -0.93 to 0.66], and [0.25; -0.28 to 0.78], respectively. The corresponding CCCs were 0.803, 0.514, and 0.631. This study found weak agreement between Anterion and Pentacam AXL, IOLMaster 700, and Orbscan IIz devices regarding WTW distance measurements in refractive surgery candidates. Therefore, it is not recommended to use Anterion's WTW measurements interchangeably with the other three devices, particularly for phakic intraocular lens sizing.

The comparison of white-to-white via triple person-times caliper measuring and machine-measuring in V4c implantable collamer lens implantation

This study aimed to compare the differences and characteristics of white-to-white (WTW) values obtained before V4c implantation using triple person-times caliper, IOL-Master 700, Pentacam HR, and UBM, and to assess their correlation with vaulting. A total of 930 myopia patients (1842 eyes) who were interested in undergoing ICL surgery were assessed before the procedure using various instruments. The WTW measurements were obtained using a triple person-times caliper, Pentacam HR, and IOL-Master 700, whereas the angle-to-angle (ATA) measurements were obtained using UBM. The size of the ICL was subsequently calculated using triple person-times caliper measurements. The vault of the ICL was assessed using Pentacam HR three months after the surgery. The WTW was determined to be 11.30 ± 0.29 mm, 11.43 ± 0.29 mm, and11.86 ± 0.38 mm, respectively, using the triple person-times caliper, Pentacam HR, and IOL-Master 700. The measurement of ATA was 11.57 ± 0.51 mm, as done by UBM. The ICL vault was measured to be 400.97 ± 198.46 µm when examined with Pentacam HR three monthsafter the procedure. The linear regression analyses of ICL size and WTW of triple person-times caliper, ICL vault and WTW were (R = 0.703, p < 0.001; R = 0.0969, p < 0.001) respectively. The highest correlation was found between IOL-Master and Pentacam HR (r = 0.766, p = 0.000). The lowest correlation was found between UBM and Pentacam HR (r = 0.358, p = 0.002). Bland–Altman analysis showed that the 95% limits of agreement (LoA) were the triple person-times caliper and Pentacam HR (– 0.573, 0.298) and the triple person-times caliper and UBM (– 1.15, – 0.605). This indicated a strong agreement between the triple person-times caliper and Pentacam HR and a lack of agreement between the triple person-times caliper and UBM. Triple person-times caliper measurements offer excellent maneuverability, practicality, and reliable outcomes for determining ICL vaults. Measurements obtained using the triple-person caliper were less differece than those obtained using the Pentacam HR.

Predicting post-operative vault and optimal implantable collamer lens size using machine learning based on various ophthalmic device combinations

BackgroundImplantable Collamer Lens (ICL) surgery has been proven to be a safe, effective, and predictable method for correcting myopia and myopic astigmatism. However, predicting the vault and ideal ICL size remains technically challenging. Despite the growing use of artificial intelligence (AI) in ophthalmology, no AI studies have provided available choices of different instruments and combinations for further vault and size predictions. This study aimed to fill this gap and predict post-operative vault and appropriate ICL size utilizing the comparison of numerous AI algorithms, stacking ensemble learning, and data from various ophthalmic devices and combinations.ResultsThis retrospective and cross-sectional study included 1941 eyes of 1941 patients from Zhongshan Ophthalmic Center. For both vault prediction and ICL size selection, the combination containing Pentacam, Sirius, and UBM demonstrated the best results in test sets [R2 = 0.499 (95% CI 0.470–0.528), mean absolute error = 130.655 (95% CI 128.949–132.111), accuracy = 0.895 (95% CI 0.883–0.907), AUC = 0.928 (95% CI 0.916–0.941)]. Sulcus-to-sulcus (STS), a parameter from UBM, ranked among the top five significant contributors to both post-operative vault and optimal ICL size prediction, consistently outperforming white-to-white (WTW). Moreover, dual-device combinations or single-device parameters could also effectively predict vault and ideal ICL size, and excellent ICL selection prediction was achievable using only UBM parameters.ConclusionsStrategies based on multiple machine learning algorithms for different ophthalmic devices and combinations are applicable for vault predicting and ICL sizing, potentially improving the safety of the ICL implantation. Moreover, our findings emphasize the crucial role of UBM in the perioperative period of ICL surgery, as it provides key STS measurements that outperformed WTW measurements in predicting post-operative vault and optimal ICL size, highlighting its potential to enhance ICL implantation safety and accuracy.

Evaluation of Ocular Diameter Parameters Using Swept-Source Optical Coherence Tomography.

Purpose: To investigate the iridocorneal angle-to-angle (ATA), sclera spur-to-sclera spur (STS), and white-to-white (WTW) ocular diameters and their potential influence on anterior chamber intraocular lens (ACIOL) and implantable collamer lens (ICL) sizing in Chinese subjects by using a swept-source optical coherence tomography system (SS-OCT). Design: A retrospective, observational, cross-sectional study. Methods: In 60 right eyes (60 subjects), the ATA, STS, and WTW were measured in six axes (0°-180°, 30°-210°, 60°-240°, 90°-270°, 120°-300°, and 150°-330°) using SS-OCT. The ACIOL and ICL sizes were calculated based on horizontal and vertical axes anterior segment data. A paired sample t-test was used to test the differences in each parameter across the six axes, the potential difference between each pair of parameters in a given axis, and the artificial lens size difference between the horizontal and vertical directions. Pearson's correlation analysis was used to determine the potential correlation between age and AL, WTW, STS, and ATA distances. Results: ATA and STS were the longest on the vertical and shortest on the horizontal axis, while WTW was similar on both axes. These three parameters differed only in the vertical axis (F = 4.910, p = 0.008). ATA and STS were by 0.23 ± 0.08 mm (p = 0.005) and 0.21 ± 0.08 mm wider (p = 0.010) than WTW, respectively. ICL size was 0.27 ± 0.23 mm smaller when based on the horizontal than on the vertical axis parameters (p < 0.001), while ACIOL remained similar (p = 0.709). Age correlated negatively and axial length positively with all measured values. ATA, STS, and WTW correlated positively in the same axis (all p < 0.001). Conclusions: ATA and STS were longer in the vertical than in the horizontal direction, while WTW measurements remained similar. ATA and STS diameters more accurately depicted anatomic relationships for phakic IOL sizing than WTW.

The Effect of Cycloplegia on the Biometer for Optical Low-coherence Reflectometry.

The aim of this study was to compare the biometric measurements and different formulas for calculating intraocular lens (IOL) power by using the Lenstar LS900 biometer for optical low-coherence reflectometry before and after induction of cycloplegia in the adult population. In this cross-sectional study, 168 eyes of 168 healthy volunteers aged 40 - 86 years (59.22 ± 11.57) were included. Biometric measurements, including axial length (AL), anterior chamber depth (ACD), keratometry (K1 and K2), and white-to-white (WTW) were compared using a Lenstar LS900 optical biometer before and after induction of cycloplegia with 1% cyclopentolate. The IOL power was also compared using six different formulas (Barrett Universal II, Haigis, SRK/T, Hoffer Q, Holladay, and SRK-II) for the AcrySof MA60AC IOL before and after induction of cycloplegia. There were no statistically significant differences in AL, K1 and K2, or WTW measurements before and after induction of cycloplegia. There was a significant increase only in ACD from the biometric parameters after the induction of cycloplegia (p < 0.05). Despite this change, there were no significant changes in IOL power calculations using the six different formulas before and after induction of cycloplegia. This study demonstrated that IOL power measurements using the Lenstar LS900 can be performed after cycloplegia.

Agreement of anterior segment measurements between LenStar LS 900 optical biometer and OPD Scan III wavefront aberrometer devices in eyes with cataract.

To compare the inter-device agreement of anterior eye segment measurements between LenStar LS 900 optical biometer and OPD Scan III wavefront aberrometer. This is a retrospective study involving 59 patients (78 eyes) with cataract. Their angle Alpha, angle Kappa, pupil size and white-to-white (WTW) distance were measured by LenStar LS 900 optical biometer and OPD Scan III wavefront aberrometer, respectively, and pairwise agreement comparisons were performed between them. The most agreement of various parameters was occurred, with intraclass correlation coefficient (ICC) of WTW=0.930; angle Alpha=0.853; angle Kappa=0.898; and pupil size=0,976 in bright environment. Furthermore, in dark environment, the ICC of WTW, angle Alpha, angle Kappa, and pupil size were 0.927, 0.791, 0.915, and 0.990, respectively. Bland-Altman plot showed similar excellent agreement in the outcomes of the two devices for these measurements testing. There was an excellent agreement between the LenStar LS 900 optical biometer and OPD Scan III wavefront aberrometer for WTW, angle Alpha, angle Kappa, and pupil size measurements. In clinical practice, these measurements obtained by LenStar LS 900 optical biometer and OPD Scan III wavefront aberrometer can be used interchangeably.

Comparison of white-to-white measurements using four devices and their determination of ICL sizing

BackgroundTo compare the measurements obtained from the Orbscan II, IOLMaster 700, Pentacam AXL, and Castroviejo caliper and their effects on calculating the recommended implantable collamer lens (ICL) size and postoperative vault measurements.MethodsThis is a retrospective cross-sectional study of patients who underwent ICL surgery by a single surgeon from March 1, 2018 to July 31, 2021. Records were reviewed for the anterior chamber depth (ACD) and white-to-white (WTW) measurements obtained from the Orbscan II, IOLMaster 700, Pentacam AXL, and Castroviejo caliper (WTW only). These were used to calculate the recommended ICL size. The actual ICL size implanted, and vault measurements obtained one month postoperatively were also collected.ResultsOne hundred seven eyes with a mean age of 27.9 ± 7.7 years were included in the study. Mean WTW measurements were significantly different between devices (P < 0.0001), with the IOLMaster 700 having the highest value (12.14 ± 0.04 mm) and the caliper having the lowest value (11.45 ± 0.04 mm). Mean ACD measurements were the lowest in Orbscan II (3.12 ± 0.25 mm) and the highest in Pentacam AXL (3.16 ± 0.24 mm). The Pentacam AXL produced an ICL size similar to the Orbscan in 69.2% of eyes. The IOLMaster yielded an ICL measurement one size larger than Orbscan-based calculations in 64.5% of eyes. Using the Orbscan WTW and ACD, the desired vault of 0.25 to 0.75 mm and 0.25 to 1.00 mm was achieved in 70% and 91% of eyes, respectively. Substituting caliper WTW to IOLMaster 700 or Pentacam AXL WTW increases the percentage of achieving the desired vault to 80%, similar to the Orbscan.ConclusionsThe Orbscan II, IOLMaster 700, and Pentacam AXL cannot be used interchangeably for calculating ICL sizing. Combining the WTW from caliper measurement with the ACD of the IOLMaster 700 or Pentacam AXL could improve ICL sizing and achieve a higher percentage of eyes with the desired vault.

Assessing the Efficacy of Four Diagnostic Devices and Four Nomograms in Posterior Chamber Phakic Intraocular Lens Size Selection.

To assess the efficacy of different devices and nomograms in predicting the most optimal Implantable Collamer Lens (ICL) (STAAR Surgical) size. This retrospective study includes 73 patients (142 eyes) who underwent ICL placement surgery. Anterior segment measurements were obtained by the OPD-Scan III (Marco), the Lenstar LS 900 (Haag-Streit AG/Alcon Laboratories, Inc), the Galilei G4 (Ziemer), and the VuMax ultrasound biomicroscopy device (UBM) (Sonomed Escalon). The efficacy of the four devices and four nomograms was assessed by comparing the indicated ICL sizes to the patient's postoperative vault measurements. Using white-to-white (WTW) measurements obtained by the Lenstar LS 900 and Galilei G4 coupled with the U.S. Food and Drug Administration's (FDA) (also called the manufacturer's) nomogram predicted the highest percentage (33% and 43%) of the 13.7 mm ICL sizes, respectively. Using the VuMax UBM coupled with the Dougherty nomogram indicated the highest percentage (80%) of the 12.6 mm ICL size. The ICL sizes predicted by UBM using the Parkhurst nomogram were comparable to those deemed ideal according to postoperative vault measurements. The Parkhurst nomogram predicted the most appropriate ICL size. When using WTW measurements, the optimized WTW nomogram showed promising results, especially in eyes whose preoperative calculations suggest low postoperative vaults. Moreover, clinicians should use caution when using the FDA nomogram because it showed a propensity toward indicating oversized ICLs. [J Refract Surg. 2022;38(2):106-111.].

Agreement in anterior segment measurements between swept-source and Scheimpflug-based optical biometries in keratoconic eyes: a pilot study.

Background:Cataract surgery in keratoconic patients is challenging because of the corneal distortion, which can lead to inaccurate keratometry readings. This study is a comparison of the accuracy of keratometry readings by two types of devices in a tertiary hospital.Purpose:To evaluate the comparability of corneal power measurements, anterior chamber depth (ACD), and white-to-white (WTW) distance between Scheimpflug-based tomography (Pentacam AXL; OCULUS GmbH, Wetzlar, Germany) and swept-source optical biometry (IOLMaster 700; Carl Zeiss Meditec AG, Jena, Germany) in patients with keratoconus.Methods:This pilot, prospective, interinstrument reliability study included 30 keratoconic eyes of 15 individuals who had not undergone any kind of corneal surgery. Standard K and total refractive power (TK®) of the flattest and steepest axes of the IOLMaster 700 were compared with the standard keratometry (SimK), true net power (TNP), equivalent keratometer readings (EKR), and total corneal refractive power (TCRP) of the Pentacam. The Bland–Altman analysis was used to evaluate the agreement between the measurements of both devices. The paired-samples t-test and the Wilcoxon signed-rank test were performed to compare the mean values of the variables obtained with the devices.Results:The K1 value of the IOLMaster 700 was significantly higher from EKR K1 along the 3-mm (mean difference: 0.79 diopters, p = 0.01), 4-mm (mean difference: 1.01 D, p = 0.01), and 4.5-mm zones (mean difference: 1.20 D, p = 0.01) and TNP K1 along the 3-mm (mean difference: 0.88 D, p < 0.001) and 4-mm zones (mean difference: 0.97 D, p < 0.001). The TK1 value was significantly higher from EKR K1 along the 2-mm (mean difference: 0.42 D, p = 0.04), 3-mm (mean difference: 0.83 D, p = 0.003), 4-mm (mean difference: 1.05 D, p = 0.004), and 4.5-mm zones (mean difference: 1.24 D, p = 0.005) and TNP K1 along the 3-mm (mean difference: 0.92 D, p < 0.001) and 4-mm zones (mean difference: 1.01 D, p < 0.001). The K2 value of the IOLMaster 700 was significantly higher from TK2 (mean difference: 0.11 D, p = 0.04) and all the corresponding variables of the Pentacam device. The TK2 value was significantly higher from all the corresponding variables of the Pentacam device. The Pentacam also yielded significantly lower values for the WTW distance (mean difference: 0.31 mm, p < 0.001) and no significant difference in terms of ACD values (p = 0.9).Conclusion:The IOLMaster measured significantly greater keratometry readings in the steep axis for all the variables studied. The keratometry and WTW measurements of the investigated devices cannot be used interchangeably in keratoconus.

Repeatability and Agreement of Horizontal Corneal Diameter Measurements Between Scanning-Slit Topography, Dual Rotating Scheimpflug Camera With Placido Disc Tomography, Placido Disc Topography, and Optical Coherence Tomography.

The purpose of this study was to assess the repeatability and agreement of horizontal white-to-white (WTW) measurements using 4 different imaging modalities including a slit-scanning elevation topographer, dual rotating Scheimpflug camera and Placido Disc tomographer, Placido Disc topographer, and anterior segment optical coherence (OCT) tomographer. In this prospective study, 33 eyes of 33 healthy subjects were scanned 3 times using each of the Orbscan IIz, Sirius, Nidek OPD III, and DRI OCT Triton devices and WTW measurements were recorded. Repeatability was assessed using the intraclass correlation coefficient (ICC), and agreement was analyzed using Bland-Altman plots. Mean WTW values obtained from the Orbscan IIz, Sirius, Nidek, and DRI OCT Triton devices were 11.76 ± 0.41, 12.10 ± 0.45, 12.14 ± 0.41, and 12.40 ± 0.48 mm, respectively. Overall, there was high repeatability, with the ICC >0.86 for all devices. The Sirius showed the highest repeatability (ICC = 0.993), and the Nidek the lowest (ICC = 0.870). All pairwise comparison showed significant differences in the mean WTW measurements ( P < 0.01) except between Sirius and Nidek ( P = 0.27). Mean differences showed that the DRI OCT Triton had the highest WTW values, followed by Nidek, Sirius, and finally by Orbscan, which provided the lowest measurements. All pairwise comparisons had wide limits of agreements (between 0.60 and 0.80 mm). In healthy subjects the 4 devices demonstrated high repeatability in WTW measurement. However, a poor agreement between the devices suggests that they should not be used interchangeably for WTW measurements in clinical practice.

Agreement of anterior segment measurements between four diagnostic imaging devices in myopic patients

ABSTRACT Purpose To compare the inter-device agreement of anterior chamber depth (ACD), central corneal thickness (CCT), flat keratometry (K1), steep keratometry (K2), corneal astigmatism (ΔK), and white-to-white (WTW) measurements. Methods This is a retrospective study with 73 myopic patients (142 eyes). We extracted and compared anterior segment measurements (ACD, CCT, K1, K2, ΔK, and WTW) of four devices (OPD-Scan III, Pentacam HR, Lenstar LS 900, and Galilei G4), and performed pairwise agreement comparisons between them. Results Agreement analyses revealed that the most agreement occurred: in Pentacam HR and Galilei G4 for ACD measurements, in Pentacam HR and Lenstar LS 900 for CCT measurements, in OPD-Scan III and Galilei G4 for WTW measurements, in OPD-Scan III and Pentacam HR for K1 and K2 measurements, and OPD-Scan III and Galilei G4 for ΔK measurements. Conclusion OPD-Scan III is interchangeable with both Galilei G4 and Lenstar LS 900 for WTW measurements. OPD-Scan III and the Pentacam-HR are interchangeable in K1, K2, and ΔK measurements. OPD-Scan III and Lenstar LS 900, and OPD-Scan III and Galilei G4 are interchangeable in K1 and ΔK measurements, respectively.

Comparative analysis of two optical biometry devices: high wavelength swept source OCT versus partial coherence interferometry

PurposeTo study the reproducibility of measurements performed with a recently developed multimodal high resolution swept source optical coherence tomography (SSOCT) and to make comparisons with a partial coherence interferometry (PCI) biometer.MethodsOne hundred and fifty-two eyes of 152 subjects were involved in this study with a mean age of 65.71 ± 13.86 years (26–85 years). Anterior surface keratometry (K), anterior chamber depth (ACD), white-to-white (WTW) and axial length (AL) values were recorded by the SSOCT (ANTERION, Heidelberg Engineering Ltd, Germany) and PCI (IOLMaster 500, version 5.5, Carl Zeiss Meditec, Germany). Intraocular lens (IOL) power was calculated based on ANTERION and IOLMaster keratometry values by using five traditional vergence formulas.ResultsAnterior surface simulated keratometry values did not differ significantly between the IOLMaster and ANTERION (P > 0.05). AL measurements were successful in 95% of the cases both with the SSOCT and PCI. No significant difference was disclosed between the two instruments (P = 0.229). For WTW measurements, a significant difference was observed between the two optical biometers (P < 0.0001). The difference between PCI and SSOCT in IOL powers was statistically significant for SRK/T, Hoffer and Holladay formulas (P < 0.001).ConclusionOur results implicated an overall good reproducibility of anterior keratometry, AL, ACD and WTW measurements for IOLMaster and ANTERION. The discrepancies between their measurements resulted in significant difference in the calculated IOL power for SRK/T, Hoffer and Holladay formulas, but not for Haigis formula.

Inter-device measurement variability of vital data parameters for keratorefractive and cataract refractive surgery.

Introduction:The measurements of corneal white-to-white (WTW) diameter and pupil size are critical for decision making in refractive surgery. Currently, automatic measurement of keratometry, corneal WTW, and pupil size are implemented in several ocular devices. The purpose of this study was to examine the agreement between two commonly used devices, an autorefractor and an optical biometer, for these parameters.Methods:Measurements were performed with both a Lenstar LS-900 and Nidek ARK-1 by an experienced examiner in random order. The devices were placed in close proximity within the same dimly lit room.Results:The measurements of 65 right eyes were analyzed. The results of the flat, steep, and mean keratometric reading were not significantly different (p = 0.96, p = 0.90, p = 0.93, respectively). Corneal WTW distances showed only moderate agreement between devices and were found to be significantly different (r = 0.8071; p < 0.01). Pupil diameters showed poor agreement between devices and were significantly different (r = 0.4890; p < 0.01). Agreement between implantable contact lens sizing, based on the measurements obtained by the two devices, was achieved for 19 of the 51 eyes (37.3%).Conclusion:We found a significant difference in WTW and pupil size measurements between ARK-1 and Lenstar. Results for both of the devices cannot be considered interchangeable for these data parameters.

Comparing the Lenstar Optical Biometer and the Verion Image-Guided System for intraocular lens power calculation

Introduction: This study aims to evaluate the accuracy of the measurement parameters of the new Verion Image Guided System compared with an established standard of care.&#x0D; Purpose: To compare the keratometry (K) and white-to-white (WTW) measurements obtained from the Lenstar Optical Biometer (LS) with those from the Verion Image-Guided System (VR) and their effect on intraocular lens (IOL) power calculation.&#x0D; Design: Prospective comparative case series.&#x0D; Materials and methods: Sixty patients going for cataract surgery had biometry measurements and IOL calculation with the LS. Axial length from LS was used together with K and WTW measurements from VR for IOL calculation as well. IOL selection was done using the Barrett Universal II formula targeting emmetropia. The prediction error (PE) within 0.25 D, 0.5 D, and 1 D of refractive target and the mean absolute error (MAE) were calculated for both the LS and VR.&#x0D; Results: Keratometry measurements and steep axis from the VR were closely correlated with the LS (Pearson correlation coefficient K1, r = 0.958; K2, r = 0.952; axis, r = 0.950). The WTW measurements were less so (WTW, r = 0.471). The MAE was 0.317 and 0.347 for LS and VR, respectively. PE within 0.25 D was 48.3% and 40%; within 0.5 D was 83.3% and 76.7%; and within 1 D was 98.3% and 96.7% for LS and VR, respectively. There was no statistically significant difference in MAE between the LS and VR (p = 0.74)&#x0D; Conclusion: Using the K and WTW measurements from the Verion Image-Guided System for IOL power calculation did provide comparable results with the Lenstar. The Lenstar had a higher proportion of eyes within 0.5 D of refractive target but the difference was not statistically significant.&#x0D;

Anterior chamber lens sizing: Comparison of white-to-white and scleral spur-to-scleral spur methods.

To determine the most accurate method of estimating scleral-spur-to-scleral-spur (STS) distance for ophthalmologists without access to an anterior chamber optical coherence tomography (AS-OCT) instrument when selecting an anterior chamber intraocular lens (AC IOL). Robert Cizik Eye Clinic, Houston, TX. Prospective cohort study. The eyes of 65 participants aged 18 years or older were imaged by the Lenstar LS 900 optical biometer and CASIA SS-1000 swept-source Fourier-domain AS-OCT. Eyes were excluded if the anterior segment anatomy was significantly altered and the angle could not be visualized. When both eyes were eligible, 1 eye was randomly selected. The white-to-white (WTW) distance, STS distance, and axial length were recorded and compared. The difference between STS and horizontal WTW was calculated for each meridian. The mean (±SD) differences, 95% limits of agreement, and Bland-Altman agreement were computed for each pair of STS and WTW measurements. The study comprised 65 eyes of 65 participants. In nearly every case, WTW + 0.5 and WTW + 1 overestimated STS. The horizontal WTW without adjustment was the best predictor of STS. The WTW best corresponded to the vertical STS meridian (6 to 12 o'clock) and not the horizontal meridian (3 to 9 o'clock), along which AC IOLs are traditionally placed. The horizontal WTW method without an adjustment factor most accurately estimated STS distance and should be used to select AC IOL size when AS-OCT is not available. If AS-OCT is available, it should be used instead. In addition, AC IOLs should be placed in a vertical orientation rather than the traditional horizontal orientation to minimize sizing errors.

Predictability of the vault after posterior chamber phakic intraocular lens implantation using anterior segment optical coherence tomography

To determine whether vault measurements after placement of a hole implantable collamer lens (hole ICL) (KS-AquaPORT) can be predicted by angle-to-angle (ATA) and white-to-white (WTW) measurements obtained with anterior segment optical coherence tomography (AS-OCT). Sanno Hospital, Tokyo, Japan. Retrospective case series. Eyes were observed for 3months after hole ICL implantation for myopia or myopic astigmatism. Central vault, ATA, and WTW measurements were obtained before and after surgery using the swept-source AS-OCT CASIA2 system. The study included 44 eyes (23 patients). The mean patient age and preoperative spherical equivalent, ATA, and WTW values were 36.2years±8.8 (SD), -6.23±3.41 diopters (D), 12.03±0.40mm, and 11.72±0.40mm, respectively. The safety index and efficacy index 3months postoperatively were 1.13±0.21 and 0.91±0.30, respectively. Regarding predictability, 93.2% of eyes were within ±0.50 D of the attempted correctionand all eyes were within ±1.00 D. The reproducibility coefficients for the ATA distance and WTW distance were 0.998and 0.960, respectively. The mean postoperative central vault was 491.6±189.5μm. There was a significant correlation between postoperative vault and the ICL size and ATA distance (Spearman rank correlation coefficient r=0.59, P<.001) butnot between the ICL size and WTW distance (r=0.27, P=.08). The ATA measurements had higher reproducibility than the WTW measurements on AS-OCT, making it is a more important predictor of postoperative vault.

A comparative study of the discrepancy in the horizontal white-to-white measurement using Calipers vs Pentacam

Background: The accurate measurement of the horizontal corneal white-to-white (WTW) diameter is essential and has multiple applications in the field of ophthalmology whether medical or surgical. There are many means of measuring the horizontal white-to-white, which includes the Pentacam, the IOL Master and Manual Calipers. Both the Pentacam and Manual Calipers measure the external white-to-white diameter, whereas the IOL Master measures the internal white-to-white diameter. Objective: The aim of this study is to measure the accuracy of the Pentacam white-to-white camera in measuring the horizontal corneal WTW diameter in comparison to the Manual Calipers, which is considered to be the basic standard. Patients and Methods: The study was a cross sectional one, conducted at Maghrabi Eye Hospital, Cairo, Egypt. It was conducted in accordance with the ethical standards stated by the Ethical Committee of Ain Shams University. Informed consent was obtained from each participant following the explanation of the academic nature of the study. Results: Our study compared the accuracy of the Pentacam HR to the Manual Calipers and found a strong correlation between both methods regarding all parameters. A difference of 0.44 ± 0.17 mm was found between the manual calipers and the Pentacam (HVID Automated) measurements and a lesser difference of 0.24 ± 0.27 mm when comparing the manual calipers with the Pentacam manual digital calipers. On the other hand, the difference between the 2 methods of the Pentacam measurement used was 0.19 ± 0.13 mm. All of which, showed a highly significant correlation. Conclusion: The Pentacam gives larger WTW measurements than the manual calipers as it relies on the gray scale analysis of the HVID in the iris image display.