Partial Coherence Interferometry Biometer Research Articles

Repeatability and agreement of AOCT-1000 M, RTVue XR and IOL master 500 in measuring corneal thickness mapping and axial length applying principle of optical coherence tomography

PurposeTo evaluate the repeatability and agreement of Fourier-domain optical coherence tomography (AOCT-1000 M and RTVue XR) and partial coherence interferometry biometer (IOL Master 500) in measuring corneal thickness mapping and axial length respectively.MethodsCorneal thickness was measured by AOCT-1000 M and RTVue XR. Axial lengths were measured by AOCT-1000 M and IOL Master 500. The repeatability and agreement of corneal thickness and axial length were calculated in two groups of devices. The intraclass correlation coefficient (ICC) was used to verify the repeatability of the device. The 95% confidence interval of the difference compared to the set cut-off value was used to verify the agreement between the two devices.ResultsA total of 60 subjects with 58 eyes were included. The central corneal thickness measured by AOCT-1000 M and RTVue XR were 504.46 ± 42.53 μm and 504.43 ± 42.89 μm respectively. The average difference between groups was 0.03 ± 4.58 μm, and the 95% confidence interval was (-1.17, 1.24), which was far less than the set threshold value of 15 μm (P < 0.001). Both RTVue XR and AOCT-1000 M had very good ICC values of central corneal thickness (0.998 and 0.994, respectively). The average axial lengths measured by AOCT-1000 M and IOL Master 500 were 24.28 ± 1.25 mm and 24.29 ± 1.26 mm respectively and the 95% confidence interval was (-0.02, 0.01), which was less than the set threshold value of 0.15 mm (P < 0.001). The ICC for both devices were 1.000.ConclusionGood repeatability and agreement were seen in measurements of central corneal thickness and axial length by AOCT-1000 M.

Evaluation and comparison of a novel Scheimpflug‑based optical biometer with standard partial coherence interferometry for biometry and intraocular lens power calculation

In the present study, the axial length (AL), corneal curvature, anterior chamber depth (ACD) and white-to-white (WTW) distance were assessed using the Pentacam AXL (Oculus Optikgeraete GmbH), a novel Scheimpflug-based optical biometer with standard partial coherence interferometry (PCI). The Pentacam AXL and PCI biometer (IOLMaster 500; Carl Zeiss AG) were compared in terms of their intraocular lens (IOL) power calculations. The medical records of patients (eyes, n=190) who underwent cataract surgery were retrospectively reviewed. Biometry measurements involved the eyes of patients with cataract and were performed by the same examiner with the Pentacam AXL biometer and the IOLMaster 500 device. Following determination of the AL, mean keratometry (Km), ACD and WTW distance, the IOL power calculation was compared between the two devices using the Sanders, Retzlaff and Kraff theoretical (SRK/T) and Haigis formulas. The AL, Km and WTW values for the Pentacam AXL group were significantly lower compared with those of the IOLMaster 500 group. The difference was -0.02±0.04 mm, -0.20±0.28 D and -0.10±0.20 mm, respectively (P<0.001). The ACD for the Pentacam AXL group was higher compared with that of the IOLMaster 500 group with a difference of 0.02±0.13 mm (P=0.13). The IOL power calculated using the SRK/T and Haigis formulas exhibited significant differences between the two devices (t=11.48 and 10.97, respectively; P<0.001). In conclusion, the AL, ACD, WTW measurement and IOL power indicated optimal agreement and strong correlations between the two devices. However, constant optimization may be necessary for the novel biometer Pentacam AXL.

Comparison of a new swept-source optical biometer with a partial coherence interferometry

BackgroundThe purpose of this study is to compare the biometric parameters and intraocular lens (IOL) power calculation by a new swept-source optical coherence tomography (SS-OCT) biometer with those by a partial coherence interferometry (PCI) biometer.MethodsMedical records of 175 eyes from 175 patients were retrospectively reviewed. One of two monofocal IOLs (Tecnis ZCB00 or Acrysof SA60AT) were implanted in the eyes. Axial length (AL), mean keratometry (Km), J0, J45 and anterior chamber depth (ACD) were compared between PCI and SS-OCT biometers. The refractive mean error (ME) and refractive mean absolute error (MAE) were also compared. Examination failure rates were calculated in each device.ResultsOut of 175 eyes, 150 eyes were successfully examined by both devices. AL was measured slightly shorter when using SS-OCT than PCI biometer, while Km was measured higher (P < .0001, P = .03, respectively, paired t-test). J0, J45 and ACD were not significantly different between two devices. ME and MAE calculated using SRK-T, Hoffer Q, and Haigis formula were not significantly different except MAE calculated with Haigis formula for Tecnis ZCB00 IOLs (P = .03, paired t-test). The examination failure rates were 14.29 and 1.14% when using the PCI and SS-OCT biometers, respectively.ConclusionsAL and Km don’t seem to be comparable between two devices, while J0, J45, and ACD do. IOL power calculation using SRK-T and Hoffer Q was correlated between the devices. The penetration ability of a SS-OCT biometer is superior.

Accuracy of SS-OCT biometry compared with partial coherence interferometry biometry for combined phacovitrectomy with internal limiting membrane peeling

To evaluate the accuracy of a swept-source optical coherence tomography (SS-OCT) biometer compared with a standard partial coherence interferometry (PCI) biometer in terms of phacovitrectomy for vitreomacular pathology and cataract. Department of Ophthalmology, Ludwig-Maximilians-University Munich, Germany. Prospective, nonrandomized, single center consecutive case series. Patients with age-related cataract, regular corneal astigmatism less than 1.25 diopters (D) and a clinically significant vitreomacular pathology (epiretinal membrane [ERM], macular hole, or vitreomacular traction [VMT] syndrome) who had combined phacovitrectomy with internal limiting membrane peeling were enrolled. Objective and manifest refraction, corrected distance visual acuity, SS-OCT biometry, and PCI biometry were obtained preoperatively and 3months postoperatively. The refractive prediction error and mean absolute error (MAE) were calculated for each biometric device with the Haigis formula. The percentage of eyes with a prediction error within ±0.50 D or less were calculated. The study comprised 79 eyes of 79 patients. The mean refractive prediction error of all eyes was -0.27 D ± 0.76 (SD) for the PCI biometer and -0.28±0.57 D for theSS-OCT biometer (P=.802), and the MAE was 0.61±0.53D and 0.46±0.43 D, respectively (P=.012). A prediction error within ±0.50 D or less was observed in 55 eyes (70%) with the SS-OCT biometer compared with 42 eyes (53%) with the PCI biometer (P=.0001). The MAE with the SS-OCT biometer was statistically significantly lower in eyes with ERMs or macular holes compared with the PCI biometer (P=.043 and P=.028, respectively), whereas no statistically significant difference was observed in eyes with VMT syndrome (P=.286). The SS-OCT biometer showed a statistically significant lower MAE compared with the PCI biometer, and it is recommended for precise intraocular lens power calculations in combined phacovitrectomy for cataract and vitreomacular diseases.

Comparison of a new Scheimpflug imaging combined with partial coherence interferometry biometer and a low-coherence reflectometry biometer

To evaluate the repeatability of a new biometer using Scheimpflug technology combined with partial coherence interferometry (PCI) (Pentacam AXL) and its agreement with a device based on optical low-coherence reflectometry (OLCR), the Allegro Biograph. Oftalvist Centro Integral Ocular Jerez, Jerez de la Frontera, Spain. Evaluation of a diagnostic test. The mean keratometry (K), central corneal thickness (CCT), anterior chamber depth (ACD), and axial length (AL) were measured with the 2 devices 3 times by the same examiner in 2 groups (patients with cataract and patients without cataract). The repeatability was determined using the within-subject standard deviation, test-retest repeatability, coefficient of variation, and intraclass correlation coefficient. The correlation was evaluated with the Pearson coefficient and interchangeability with the Bland-Altman plot. Eighty eyes (40 eyes in each group) of 80 patients were analyzed. Significant differences were found between the Scheimpflug-PCI device and the OLCR device for mean K in the normal group (P<.001) and for CCT in the normal group (P<.05) and the cataract group (P<.001). There were no differences between devices in ACD and AL in either group. The repeatability between devices was similar. Although a significant correlation between devices was found for all measurements (all P<.001), wide limits of agreement were found in both groups for all biometric parameters. The Scheimpflug-PCI and OLCR devices showed excellent intravisit repeatability and high correlation for mean K, CCT, ACD, and AL in healthy and cataractous eyes. No differences were found in AL; however, the 2 devices might not be interchangeable.

Axial length measurements: Comparison of a new swept-source optical coherence tomography–based biometer and partial coherence interferometry in myopia

To compare axial length (AL) measurements between a swept-source optical coherence tomography (SS-OCT) biometer (IOLMaster 700) and a partial coherence interferometry (PCI) biometer (IOLMaster, version 5.4) in myopic eyes. Severance Hospital, Yonsei University, Seoul, South Korea. Prospective evaluation of a diagnostic test. This study enrolled patients with a diagnosis of myopia in their medical records. Two consecutive AL measurements were performed in each eye in random order using the 2 biometers. Subanalysis was performed according to lens status, fixation status, degree of myopia, and the presence of posterior staphyloma. The interdevice agreement was evaluated with Bland-Altman analyses and paired t tests. This study comprised 219 eyes of 117 patients. During a fixation check using SS-OCT, 19.6% of eyes showed fixation loss. Overall, the SS-OCT biometer showed a longer AL than the PCI biometer. (P<.001) In a subanalysis that categorized eyes according to lens status, fixation status, degree of myopia, and the presence of posterior staphyloma, the SS-OCT biometer also showed longer ALs than the PCI biometer. Ofeyes with good fixation, significant differences in AL measurements between devices were detected for those with posterior staphyloma (P<.001) but not for those without posterior staphyloma (P=.104). The 2 devices showed differences in AL measurements in myopic eyes. Fixation status and the presence of posterior staphyloma were important factors in these differences.For myopic eyes with posterior staphyloma, the SS-OCT biometer is expected to produce more precise AL measurements because it allows evaluation of the fixation status.

Comparison of a new optical biometer and a standard biometer in cataract patients.

BackgroundCataract surgery is the most common surgical procedure in ophthalmology. Biometry data and accurate intraocular lens (IOL) calculations are very important in achieving the desired refractive outcomes. The aim of this study was to compare measurements using a new optical low coherence reflectometry (OLCR) biometer (OA-2000) and the gold standard partial coherence interferometry (PCI) optical biometer (IOLMaster 500).MethodsOcular biometry of cataract patients were measured by the OA-2000 and IOLMaster 500 to compare keratometry (K), axial length (AL), anterior chamber depth (ACD), white-to-white (WTW) diameter, and IOL power using the SRK/T formula.ResultsOne hundred and two eyes of 68 cataract patients were evaluated with the two optical biometers. The mean values of the AL, K, ACD, and WTW differed very little (OCLR biometer, 23.12 mm, 44.50 diopters (D), 3.06, and 11.64 mm, respectively; PCI biometer, 23.18 mm, 44.6 D, 3.15, and 11.86 mm, respectively), but the differences were significant (all, p ≤ 0.05). The AL, K, and ACD showed excellent correlations (r = 0.999, 0.980, and 0.824, respectively; all p < 0.001); however, there was a weak correlation of the WTW diameter between the two devices (r = 0.256). The IOL powers using the SRK-T formula derived from both instruments were very similar, with an excellent correlation (r = 0.989). The mean difference between the two instruments was 0.32 D.ConclusionsThe OLCR biometer showed very a strong agreement with the standard PCI optical biometer for almost all ocular biometry measurements, except for the WTW diameter.Trial registrationTCTR20160614003; date 06/09/2016; ‘retrospectively registered’.

Comparability of an image-guided system with other instruments in measuring corneal keratometry and astigmatism

To test whether keratometry (K) and astigmatism measurements provided by the VerionReference Unit (an image-guided system) compared well with the Tonoref II automated tonometer-refractometer, IOLMaster partial coherence interferometry (PCI) biometer, AL-Scan optical biometer, Pentacam rotating Scheimpflug camera, and OPD Scan III wavefront aberrometer. Augenklinik am Neumarkt, Cologne, Germany. Retrospective case series. Patients having routine cataract surgery had standard preoperative assessment including biometry measurement with all study devices. The K values, power of astigmatism, axis, and the lens power of an imaginary intraocular lens (IOL) were analyzed for each device. One hundred five eyes of 62 patients with a mean age of 68.5years±11.9 (SD) (range 27.2 to 89.7years) were included in the study. The mean differences in flat K readings between the image-guided system and the tonometer-refractometer, PCI biometer, optical biometer (2.4 and 3.2mm), rotating Scheimpflug camera, and wavefront aberrometer were -0.03mm, 0.00mm, 0.01mm (both 2.4 and 3.2mm), -0.03mm, and -0.01mm, respectively (P<.001). Differences were slightly greater for steep K readings as follows: -0.04mm, -0.01mm, -0.02 (optical biometer 2.4mm), -0.03mm (optical biometer 3.2mm), -0.04mm, and -0.06mm, respectively (P<.001). The calculated power of an imaginary IOL from the study devices fell within 0.28 diopter of one another (P>.05). The image-guided system compared well with and provided astigmatism measurements similar to those of currently available diagnostic measurement devices. This system can aid appropriate preoperative IOL power calculations. Drs. Schultz, Oberheide, and Kermani have received honoraria from Alcon Pharma GmbH for corporate presentations.

Comparison of 3 biometry devices in cataract patients

Accurate biometry is an obligatory preoperative measurement for refractive surgery as well as cataract surgery. A new device based on partial coherence interferometry was compared with 2 currently used biometry devices. Department of Ophthalmology, Saarland University Medical Center, Homburg, Germany. Prospective case series. Eyes of cataract patients were examined with a functional prototype of the new optical low-coherence reflectometry (OLCR) biometer OA-2000, the standard OLCR biometer Lenstar, and the partial coherence interferometry (PCI) biometer IOLMaster. The results were compared using a Wilcoxon-Mann-Whitney U test and Pearson correlation calculations. A total of 138 eyes of 74 cataract patients were examined. Pearson correlation showed excellent correlation for axial length, anterior chamber depth and keratometry among the 3 devices tested. The highest correlation was found between standard OLCR biometer and PCI biometer for AL, R1, and R2 (r = 1.0, r = 0.936, r = 0.952, respectively; all P ≤ .001). For anterior chamber depth (ACD), the highest correlation was found between the standard OLCR biometer and the new OLCR biometer (r = 0.943; P ≤ .001). The mean values of AL/ACD/R1/R2 differed very little, but the differences were significant (all P ≤ .05) (new OLCR biometer 23.31/3.21/7.74/7.64 mm; standard OLCR biometer 23.30/3.13/7.80/7.60 mm; PCI biometer 23.37/3.00/7.78/7.6 mm). Compared with other clinical instruments, the new OLCR biometer generated the most accurate results. Differences especially in measurement of axial length were statistically but not clinically significant. The new OLCR biometer yielded results that correlated very well with the values of the PCI biometer and standard OLCR biometer. None of the authors has a financial or proprietary interest in any material or method mentioned.

Clinical comparison of a new swept-source optical coherence tomography–based optical biometer and a time-domain optical coherence tomography–based optical biometer

To evaluate the repeatability and reproducibility of a newer swept-source optical biometer and to compare it with a standard partial coherence interferometry (PCI) biometer. Siriraj Hospital, Mahidol University, Bangkok, Thailand. Prospective comparative study. One hundred eyes from 100 cataract patients were enrolled in this study. Each patient was measured with 2 optical biometers, a newer swept-source optical biometer (IOLMaster 700) and a standard partial coherence interferometry biometer (IOLMaster 500) by 2 independent operators. The keratometry, axial length (AL), anterior chamber depth, white-to-white corneal diameter, and intraocular lens (IOL) power, calculated by the SRK/T and the Haigis formulas for each device, were recorded. Intraoperator repeatability and interoperator reproducibility of both devices were analyzed using intraclass correlation coefficients (ICCs). Agreement of ocular biometry and IOL power between the 2 devices was evaluated using the Bland-Altman method. The repeatability and reproducibility of the swept-source and standard biometers were high for all ocular biometry parameters (ICC, 0.93-1.00). The agreement between the 2 biometers was also high (ICC, 0.92-1.00). The IOL powers obtained from both devices were not distinct. Because of the density of the cataracts, the AL in 5 eyes could be measured only by the swept-source biometer. Repeatability and reproducibility of a swept-source optical biometer was excellent and agreement with a standard biometer was very high. Better lens penetration ability and AL measurements were obtained with the swept-source biometer than with the standard biometer. No author has a financial or proprietary interest in any material or method mentioned.

Biometry and intraocular lens power calculation results with a new optical biometry device: Comparison with the gold standard

To evaluate the agreement in axial length (AL), keratometry (K), anterior chamber depth (ACD) measurements; intraocular lens (IOL) power calculations; and predictability using a new partial coherence interferometry (PCI) optical biometer (AL-Scan) and a reference (gold standard) PCI optical biometer (IOLMaster 500). Service d'Ophtalmologie, Hopital Bicêtre, APHP Université, Paris, France. Evaluation of a diagnostic device. One eye of consecutive patients scheduled for cataract surgery was measured. Biometry was performed with the new biometer and the reference biometer. Comparisons were performed for AL, average K at 2.4 mm, ACD, IOL power calculations with the Haigis and SRK/T formulas, and postoperative predictability of the devices. A P value less than 0.05 was statistically significant. The study enrolled 50 patients (mean age 72.6 years±4.2 SEM). There was a good correlation between biometers for AL, K, and ACD measurements (r=0.999, r=0.933, and r=0.701, respectively) and between IOL power calculation with the Haigis formula (r=0.972) and the SRK/T formula (r=0.981). The mean absolute error (MAE) in IOL power prediction was 0.42±0.08 diopter (D) with the new biometer and 0.44±0.08 D with the reference biometer. The MAE was 0.20 D with the Haigis formula and 0.19 with the SRK/T formula (P=.36). The new PCI biometer provided valid measurements compared with the current gold standard, indicating that the new device can be used for IOL power calculations for routine cataract surgery. No author has a financial or proprietary interest in any material or method mentioned.

Errors Associated with IOLMaster Biometry as a Function of Internal Ocular Dimensions

PurposeTo evaluate the error in the estimation of axial length (AL) with the IOLMaster partial coherence interferometry (PCI) biometer and obtain a correction factor that varies as a function of AL and crystalline lens thickness (LT). MethodsOptical simulations were produced for theoretical eyes using Zemax-EE software. Thirty-three combinations including eleven different AL (from 20mm to 30mm in 1mm steps) and three different LT (3.6mm, 4.2mm and 4.8mm) were used. Errors were obtained comparing the AL measured for a constant equivalent refractive index of 1.3549 and for the actual combinations of indices and intra-ocular dimensions of LT and AL in each model eye. ResultsIn the range from 20mm to 30mm AL and 3.6–4.8mm LT, the instrument measurements yielded an error between −0.043mm and +0.089mm. Regression analyses for the three LT condition were combined in order to derive a correction factor as a function of the instrument measured AL for each combination of AL and LT in the theoretical eye. ConclusionsThe assumption of a single “average” refractive index in the estimation of AL by the IOLMaster PCI biometer only induces very small errors in a wide range of combinations of ocular dimensions. Even so, the accurate estimation of those errors may help to improve accuracy of intra-ocular lens calculations through exact ray tracing, particularly in longer eyes and eyes with thicker or thinner crystalline lenses.

Differences in corneal astigmatism between partial coherence interferometry biometry and automated keratometry and relation to topographic pattern

To compare the corneal astigmatism values obtained with a partial coherence interferometry (PCI) biometer and an automated keratometer and to evaluate the association between these differences and corneal topographic patterns. Department of Ophthalmology, Guro Hospital, Korea University College of Medicine, Seoul, Korea. Comparative case series. Corneal astigmatism was measured by PCI biometry (IOLMaster) and automated keratometry (RK-F1 autorefractor). Eyes were divided into 3 groups based on the difference in absolute astigmatism values between PCI biometry and automated keratometry (ie, PCI biometry - automated keratometry) as follows: Group 1, more than 0.25 diopter (D); Group 2, within ±0.25 D; Group 3, less than -0.25 D. The topographic maps were grouped into patterns of round, oval, symmetric bow tie, asymmetric bow tie, and irregular. Distributions of topographic patterns according to group and astigmatism values by topographic patterns were evaluated. The study enrolled 312 eyes. The most common pattern was the asymmetric bow tie (34.6%) followed by symmetric bow tie (20.5%), round (18.9%), irregular (16.3%), and oval (9.6%). The asymmetric bow-tie pattern was the most common in Group 1 and Group 2 (36.1% and 50.0%, respectively); however, in Group 3, the symmetric bow-tie pattern was the most common (32.8%). The distribution of topographic patterns by groups was statistically significantly different (P=.015, Pearson chi-square test). The difference in corneal astigmatism between the PCI biometer and automated keratometer may depend on the corneal topography pattern.

Comparison of partial coherence interferometry and ultrasound for anterior segment biometry

To assess the performance of a partial coherence interferometry (PCI)-based device for the determination of anterior segment biometry. Clinica Centrofama, Cartagena, Murcia, Spain. Central corneal thickness (CCT), anterior chamber depth (ACD), and lens thickness (LT) were measured with the ACMaster PCI anterior segment biometer and an Echoscan US-1800 ultrasound (US) biometer/pachymeter with and without cycloplegia. To determine the precision of the instruments, the same examiner took 30 consecutive CCT, ACD, and LT measurements in a single subject under the same conditions and with and without cycloplegia. The same measurements were performed in additional subjects. Twenty-one eyes (16 subjects) were evaluated. Repeated measurements of the single subject yielded a standard deviation of 4.0 microm for CCT, 106.0 microm for ACD, and 323.0 microm for LT; there were many peaks, mainly in the last 10 readings. There was a high correlation between CCT measurements with both systems with and without cycloplegia (r(2)>0.93), with the US system giving higher values. Differences were significant (P< .001), but not consistent, throughout the range of corneal thicknesses and were greater for thicker corneas. Differences in ACD and LT measurements were similar. Agreement between systems in ACD and LT measurements was considerably lower than for CCT measurements. The PCI biometer provided precise CCT measurements. The ACD and LT measurements had a higher variance. Differences in CCT measurements between the 2 systems were greater for thicker corneas, with higher values with the US system.