Partial Coherence Interferometry Research Articles

Comparison of intraocular lens power calculation methods after myopic laser refractive surgery without previous refractive surgery data

To compare the accuracy of intraocular lens (IOL) power calculation methods for post-myopic excimer laser surgery patients without previous refractive surgery data using the Holladay IOL Consultant Program and the American Society of Cataract and Refractive Surgery (ASCRS) IOL Power Calculator. Wang Vision Cataract and LASIK Center, Nashville, Tennessee, USA. Case series. Eight methods were used to calculate IOL power: Holladay 2 partial coherence interferometry (PCI)-K, Holladay 2 FlatK, Wang-Koch-Maloney, Shammas No-History, Haigis-L, ASCRS-Average, ASCRS-Min, and ASCRS-Max. The optimum IOL power corresponding to the target refraction was back-calculated using the stable post-cataract surgery refraction and implanted IOL power. Using the optimum IOL power, the predicted IOL power error and the resultant refractive error with each method were calculated and compared. The Holladay 2 FlatK method was most accurate for IOL power calculation, followed by the Holladay 2 PCI-K, ASCRS-Min, Wang-Koch-Maloney, ASCRS-Average, Shammas No-History, Haigis-L, and ASCRS-Max. Statistically significant differences were observed between Holladay 2 FlatK and Holladay 2 PCI-K (P<.05), Wang-Koch-Maloney and ASCRS-Average (P<.05), and Haigis-L and ASCRS-Max (P<.01). No statistically significant differences were observed between the Holladay 2 PCI-K, ASCRS-Min, and Wang-Koch-Maloney or between the ASCRS-Average, Shammas No-History, and Haigis-L (both P>.05). The Holladay 2 FlatK method provided the most accurate IOL power in eyes without previous myopic laser surgery data. If the Holladay IOL Consultant Program is unavailable, the ASCRS methods can be used; the ASCRS-Min represents the most accurate method.

Comparison of the New Biometer OA-1000 with IOLMaster and Tomey AL-3000

Background: The OA-1000 (Tomey, Japan) is a new optical biometer, which allows measurements of axial length (AL), anterior chamber depth (ACD) and corneal thickness (CT) due to partial coherence interferometry (PCI) technology. The aim of this study was to compare the OA-1000 results with those obtained with the IOLMaster and contact applanation A-scan ultrasonography.Methods: We examined 133 eyes of 75 patients with age related cataract. Mean age was 72.0 ± 9.5 years. Biometry measurements of AL and ACD were performed with the Tomey OA-1000 based on PCI, the IOLMaster based on PCI (AL) and slit projection (ACD), and the Tomey AL-3000 based on contact applanation A-scan ultrasonography.Results: Mean AL using the IOLMaster was 23.21 ± 1.08 mm, using the AL-3000 was 22.79 ± 1.04 mm, using the OA-1000 it was 22.97 ± 1.1 mm. Mean ACD using the IOLMaster was 2.99 ± 0.41 mm, using the OA-1000 3.40 ± 0.46 mm, using the Tomey AL-3000 it was 2.93 ± 0.43 mm. Mean difference between the AL and ACD measured with the OA-1000 and the IOLMaster was 0.22 ± 0.047 mm and 0.40 ± 0.33 mm, between OA-1000 and the AL-3000 it was 0.19 ± 0.23 mm and 0.47 ± 0.33 mm, and between IOLMaster and AL-3000 it was 0.42 ± 0.23 and 0.09 ± 0.36 mm. For AL the correlation coefficient R between IOLMaster and OA-1000 was 0.999, between IOLMaster and AL-3000 it was 0.976, between AL-3000 and OA-1000 it was 0.977. For ACD R between IOLMaster and OA-1000 was 0.735, between IOLMaster and AL-3000 it was 0.822, between AL-3000 and OA-1000 it was 0.716 (all p < 0.001).Conclusions: Compared with other used clinical instruments the OA-1000 generates accurate results. Although differences were found, the OA-1000 provided results that correlated well with the values of IOLMaster and AL-3000.

Reproducibility of a Long-Range Swept-Source Optical Coherence Tomography Ocular Biometry System and Comparison with Clinical Biometers

To demonstrate a novel swept source optical coherence tomography (SS-OCT) imaging device using a vertical cavity surface-emitting laser (VCSEL) capable of imaging the full eye length and to introduce a method using this device for noncontact ocular biometry. To compare the measurements of intraocular distances using this SS-OCT instrument with commercially available optical and ultrasound biometers. To evaluate the intersession reproducibility of measurements of intraocular distances using SS-OCT. Evaluation of technology. Twenty eyes of 10 healthy subjects imaged at the New England Eye Center at Tufts Medical Center and Massachusetts Institute of Technology between May and September 2012. Averaged central depth profiles were extracted from volumetric SS-OCT datasets. The intraocular distances, such as central corneal thickness (CCT), aqueous depth (AD), anterior chamber depth (ACD), crystalline lens thickness (LT), vitreous depth (VD), and axial length (AL), were measured and compared with a partial coherence interferometry device (IOLMaster; Carl Zeiss Meditec, Inc., Dublin, CA) and an immersion ultrasound (IUS) A-scan biometer (Axis-II PR; Quantel Medical, Inc., Cournon d'Auvergne Cedex, France). Reproducibility of the measurements of intraocular distances, correlation coefficients, and intraclass correlation coefficients. The standard deviations of the repeated measurements of intraocular distances using SS-OCT were 6 μm (CCT), 16 μm (ACD), 14 μm (AD), 13 μm (LT), 14 μm (VD), and 16 μm (AL). Strong correlations among all 3 biometric instruments were found for AL (r > 0.98). The AL measurement using SS-OCT correlates better with the IOLMaster (r=0.998) than with IUS (r=0.984). The SS-OCT and IOLMaster measured higher AL values than ultrasound (175 and 139 μm, respectively). No statistically significant difference in ACD between the optical (SS-OCT or IOLMaster) and ultrasound methods was detected. High intersession reproducibility of SS-OCT measurements of all intraocular distances was observed with intraclass correlation coefficients >0.99. The SS-OCT using VCSEL technology enables full eye length imaging and high-precision, noncontact ocular biometry. The measurements with the prototype SS-OCT instrument correlate well with commercial biometers. The SS-OCT biometry has the potential to provide clinically useful comprehensive biometric parameters for pre- and postoperative eye evaluation.

Analysis of corneal biometric parameters of age-related cataract patients

Objective To analyze the distribution and correlation of corneal biometric parameters in patients with Aye-related cataract.Methods 1526 eyes of 1003 patients aged 40 years and older were recruited for this study.The corneal curvature and astigmatism were optically measured by partial coherence interferometry (IOLMaster).Statistical software package SPSS 13.0 was used to analyze statistically.Results The median age of the patients was 74 years (range 40 to 95 years).The mean of corneal curvature was (44.59 ± 1.68) diopter (D),normal distribution.There was negative relationship between age and corneal curvature (r =-0.073,P =0.000).The median corneal astigmatism was 0.95D,non-normal distribution.It was 1.0D or less in 831 eyes (54.4％),1.0D ～2.0D in 519 eyes(34.0％),and more than 2.0D in 176 eyes(11.4％).There was positive relationship between age and corneal astigmatism (r =0.143,P =0.000).With aging,the percent of with-the-rule (WTR) astigmatism decreased from 64.6％ to 22.2％,and against-the-rule (ATR) astigmatism increased from 18.8％ to 66.7％.Conclusion Corneal astigmatism less than 1.0D was present in most patients with cataract.Corneal curvature tended to decrease with aging while corneal astigmatism tended to increase.The pattern of corneal astigmatism shifted from WTR to ATR astigmatism. Key words: Cataract; Biometry; Cornea; Astigmatism; Corneal topography

Prevalence of Refractive Errors in a Multiethnic Asian Population: The Singapore Epidemiology of Eye Disease Study

To determine the prevalence of refractive errors in a multiethnic Asian population aged over 40 years and to examine secular trends and racial differences. A total of 10,033 adults (3353 Chinese, 3400 Indians, and 3280 Malays) participated in this study. Refractive error was determined by subjective refraction. Ocular biometric parameters were determined by partial coherence interferometry. Myopia and high myopia were defined as spherical equivalent (SE) of less than -0.5 diopters (D) and -5.0 D, respectively. Hyperopia was defined as SE of more than 0.5 D. Astigmatism was defined as cylinders less than -0.5 D. The prevalence of myopia, high myopia, hyperopia and astigmatism in Singapore adults aged over 40 years was 38.9% (95% confidence interval [CI] 37.1, 40.6); 8.4% (95% CI 8.0, 8.9); 31.5% (95% 30.5, 32.5); and 58.8% (95% CI 57.8, 59.9), respectively. Compared with the Tanjong Pagar Survey 12 years ago, there was a significant increase in the prevalence of astigmatism and mean axial length (AL) in Chinese adults aged over 40 years in Singapore. Chinese were most likely to be affected by myopia, high myopia, astigmatism, and had the longest AL among the three racial groups. The prevalence of myopia in Singapore adults is lower compared with the younger "myopia" generation in Singapore. The prevalence of astigmatism and mean AL have been increasing significantly within the past 12 years in the Chinese population. Chinese adults had higher prevalence of myopia, high myopia, astigmatism, as well as the longer AL compared with non-Chinese adults in Singapore.

Comparison of Automated and Partial Coherence Keratometry and Resulting Choice of Toric IOL

Consistent astigmatism correction with implantation of a toric intraocular lens (IOL) requires accurate preoperative keratometry. This article compares corneal astigmatism determined by an autokeratometer (Topcon KR-7100) and a partial coherence interferometry keratometer (IOLMaster 500) and considers if any discrepancy ultimately alters in final cylindrical power of the toric IOL for implantation. Keratometry of 235 eyes was performed using both instruments. Corneal astigmatism was transformed into vector components J0 and J45 and cylindrical power at the IOL plane calculated. Comparisons were made using paired t test and correlation and Bland-Altman analyses. Although interinstrument differences for J0 (p = 0.013), J45 (p = 0.012), and toric IOL cylindrical power (p < 0.001) were statistically significant, a high correlation for these (R = 0.96, 0.90, and 0.90, respectively) was observed. IOLMaster tended to overestimate corneal astigmatism by 0.13 (±0.31) diopters and toric IOL cylinder by 0.11 (±0.18) diopters. Difference in calculated toric IOL cylindrical power correlated poorly with corneal curvature (R = 0.007) and astigmatism (R = -0.004). The two keratometers were generally concordant in measuring corneal astigmatism. However, the resultant choice of toric IOL cylinder power differed appreciably in 40% of eyes examined. Therefore, postoperative visual outcome with toric IOL implantation may be optimized by a thorough analysis of biometry data before IOL selection, paying special attention to any difference in corneal astigmatism as measured by more than one instrument.

REFRACTIVE OUTCOMES AFTER SILICONE OIL REMOVAL AND INTRAOCULAR LENS IMPLANTATION

To evaluate the accuracy of intraocular lens (IOL) calculations in eyes undergoing silicone oil removal and IOL implantation using ultrasound biometry and partial coherence interferometry (PCI) (IOLMaster). This was a retrospective consecutive series of eyes that underwent silicone oil removal and IOL implantation from 1999 to 2009. Data were collected on preoperative and intraoperative characteristics that could affect the refractive outcome. The predicted refraction, as measured with ultrasound biometry or PCI, was compared with the postoperative refraction. Overall, the mean difference between observed and predicted refraction was -0.97 diopters (D). Thirty-five of 64 eyes (55%) were measured by ultrasound biometry, and 29 of 64 eyes (45%) were measured by PCI. The mean (SD) difference between the predicted refraction and the observed spherical equivalent was -1.34 D (2.18 D) when measured by biometry and -0.51 D (2.03 D) when measured by PCI (P = 0.13). Refractive outcomes after silicone oil removal and secondary IOL implantation are fairly accurate, with most ending up slightly myopic. Measurement by PCI may be more accurate than biometry. The IOL power should be selected to yield a target refraction about 0.5 D to 1.25 D more hyperopic than desired, depending on the method used to measure it.

Repeatability and Comparison of Peripheral Eye Lengths With Two Instruments

To assess intrasessional and intersessional repeatability of two commercial partial coherence interferometry instruments for measuring peripheral eye lengths and to investigate the agreement between the two instruments. Central and peripheral eye lengths were determined with the IOLMaster (Carl-Zeiss Meditec AG, Jena, Germany) and the Lenstar (Haag Streit, Bern, Switzerland) in seven adults. Measurements were performed out to 35° and 30° from fixation for horizontal and vertical visual fields, respectively, in 5° intervals. An external fixation target at optical infinity was used. At least four measurements were taken at each location for each instrument, and measurements were taken at two sessions. The mean intrasessional SDs for the IOLMaster along both the horizontal and vertical visual fields were 0.04 ± 0.04 mm; corresponding results for the Lenstar were 0.02 ± 0.02 mm along both fields. The intersessional SDs for the IOLMaster for the horizontal and vertical visual fields were ±0.11 and ±0.08 mm, respectively; corresponding limits for the Lenstar were ±0.05 and ±0.04 mm. The intrasessional and intersessional variability increased away from fixation. The mean differences between the two instruments were 0.01 ± 0.07 mm and 0.02 ± 0.07 mm in the horizontal and vertical visual fields, but the lengths with the Lenstar became greater than those with the IOLMaster as axial length increased (rate of approximately 0.016 mm/mm). Both the IOLMaster and the Lenstar demonstrated good intrasessional and intersessional repeatability for peripheral eye length measurements, with the Lenstar showing better repeatability. The Lenstar would be expected to give a slightly greater range of eye lengths than the IOLMaster across the visual field.

Anterior chamber depth measurement in teenagers. Comparison of two techniques

PurposeThe aim of this study is to determine the anterior chamber depth (ACD) in teenagers using two different devices: partial coherence interferometry IOLMaster (Carl Zeiss Meditec) and anterior segment optical coherence tomography (Visante™ OCT, Carl Zeiss Meditec) and to evaluate the degree of agreement between ACD measurements carried out by both instruments. MethodsIn this prospective study 68 eyes of 34 emmetropic Caucasic patients (18 girls and 16 boys) were analysed. ACD was measured from the anterior corneal surface to anterior surface of the crystalline lens. For each age the ACD size was calculated and the difference between IOLMaster and Visante-OCT measurements was analysed using Bland–Altman plot and paired t-test. ResultsFor all data the mean (SD) anterior chamber depth was 3.56 (0.19)mm with the IOLMaster and 3.65 (0.21)mm with the Visante-OCT. IOLMaster measurements were an average of 0.10 (0.12)mm less than Visante-OCT (paired t-test, p<0.0001).In our study ACD mean differences (SD) by age obtained had been −0.139 (0.163), −0.044 (0.112), −0.082 (0.054) and −0.105 (0.101) for 13, 14, 15 and 17 respectively. The 13-age group showed the larger standard deviation compared to the other groups. ConclusionsIOLMaster and Visante-OCT are good and useful non-contact methods for measuring ACD in the healthy eyes of teenagers. The measurement differences between two devices were quite small, however, they should take into account in order to calculate the power on intraocular lens. The findings provide more normative date for this age group.

White-to-white corneal diameter differences in moderately and highly myopic eyes: Partial coherence interferometry versus scanning-slit topography

To evaluate the differences between Orbscan scanning-slit topography and IOLMaster partial coherence interferometry (PCI) white-to-white (WTW) measurements in moderately and highly myopic eyes. IOBA-Eye Institute, University of Valladolid, Spain. Comparative case series. Myopic eyes were divided according to the degree of myopia as follows: Group 1 (<6.00 diopters [D]), Group 2 (between 6.00 D and 12.00 D), and Group 3 (>12.00 D). The WTW distance was measured with the scanning-slit topography and PCI devices. The study enrolled 328 eyes (64 subjects). The mean WTW in all eyes was 0.50 mm ± 0.26 (SD), lower with scanning-slit topography (11.69 ± 0.37 mm) than with PCI (12.19 ± 0.40 mm) (P<.01, paired t test). A low mean WTW was found in Group 2 (11.65 ± 0.34 and 12.15 ± 0.36 mm, scanning-slit topography and PCI, respectively) and Group 3 (11.51 ± 0.36 and 12.05 ± 0.46 mm, respectively) compared with Group 1 (11.79 ± 0.38 and 12.26 ± 0.40 mm, respectively) (P<.03, analysis of variance with Games-Howell correction). There was a low statistically significant relationship between WTW and spherical equivalent (SE) with both devices. Eyes with moderate and high degrees of myopia had lower WTW diameters than eyes with low spherical equivalent myopia measured with both devices. Scanning-slit topography provided less WTW distance than PCI in myopic eyes; thus, the devices are not clinically interchangeable.

Anterior chamber depth, intraocular lens position, and refractive outcomes after cataract surgery

To assess postoperative intraocular lens (IOL) position in relation to the cornea and iris, compare 2 devices for anterior chamber depth (ACD) measurement, and assess the impact of these factors on postoperative refraction in phacoemulsification. Department of Clinical Sciences/Ophthalmology, Umeå University Hospital, Umeå, Sweden. Evaluation of diagnostic test or technology. Biometry and measurement of the anterior segment were performed preoperatively and postoperatively with the partial coherence interferometry (PCI)-based IOLMaster and the Pentacam HR Scheimpflug device. Predicted refraction was calculated with ACD estimations according to the Haigis formula and was compared with the actual postoperative refraction. Changes in ACD and the distance between the cornea-iris and the iris-lens/IOL were assessed from Scheimpflug images. The theoretical refractive impact of differences in ACD was calculated. The mean preoperative ACD and refractive prediction error, respectively, was 3.22 mm ± 0.37 (SD) and 0.41 ± 0.43 diopters (D) for the PCI device and 3.21 ± 0.35 mm and 0.41 ± 0.41 D for the Scheimpflug device; the difference was not statistically significant. The mean ACD, cornea-iris distance, and iris-lens/IOL distance changes were 1.62 ± 0.38 mm, 0.78 ± 0.29 mm, and 0.85 ± 0.27 mm, respectively. The mean predicted refractive outcome from a 1.0 mm difference in ACD was 0.32 D. No difference was found between the measurement devices. Although the exact postoperative IOL position is difficult to predict, its impact on postoperative refraction was comparatively small compared with the impact of minor corneal curvature or axial length measurement errors.

Agreement of IOL power and axial length obtained by IOLMaster 500 vs IOLMaster 500 with Sonolink connection

The accurrate and expedient ocular biometry is essential for modern cataract surgery. IOLMaster 500, one of the most popular partial coherence interferometry (PCI) device, has been widely used. However, with the PCI device, it is difficult to obtain the axial length through densely opaque media. With the current version of IOLMaster 500, a unique feature is added to link with the Synergy immersion A-scan ultrasound (sonolink connection). In case of failure to measure axial length by IOLMaster 500, the axial length can be obtained by ultrasound, and then transferred to IOLMaster 500 for the IOL power calculation. This study aims to compare the results and evaluate the agreement between IOL power and axial length obtained by IOLMaster 500 and IOLMaster 500 with sonolink connection. A prospective study of 60 eyes in 60 mild-to-moderate cataract patients was conducted under Institutional Ethics Committee approval. Keratometry (K) and axial length (AL) of all eyes were measured using IOLMaster 500 (Carl Zeiss, Germany), then IOL power was generated using Holladay 1 formula (group 1). After 5 min, the K measurements were repeated with IOLMaster 500 and the AL were measured again using the Synergy A-scan ultrasound (Accutome, USA). Then, the AL data were transferred to IOLMaster 500 via the sonolink connection to generate the IOL power using the same setting (group 2). The IOL power and AL were compared between the two groups, and the agreement was evaluated using intraclass correlation coefficient (ICC) and the Bland-Altman method. The mean IOL power in group 1 was 21.04 + 2.36 D and group 2 was 21.03 + 2.36 D. The mean AL in group 1 was 23.35 + 0.86 mm and in group 2 was 23.36 + 0.86 mm. There was no statistically significant difference in IOL power and AL between the two groups. The agreements in IOL power and AL between both groups were high (ICCs = 0.997 for IOL power and 0.993 for AL) CONCLUSIONS: The IOL power and AL derived from both groups were similar. The agreements between them were high.

Keratometry obtained by corneal mapping versus the IOLMaster in the prediction of postoperative refraction in routine cataract surgery

To establish whether simulated keratometry values obtained by corneal mapping (videokeratography) would provide a superior refractive outcome to those obtained by Zeiss IOLMaster (partial coherence interferometry) in routine cataract surgery. Prospective, non-randomized, single-surgeon study set at the The Royal United Hospital, Bath, UK, District General Hospital. Thirty-three patients undergoing routine cataract surgery in the absence of significant ocular comorbidity. Conventional biometry was recorded using the Zeiss IOLMaster. Postoperative refraction was calculated using the SRK/T formula and the most appropriate power of lens implanted. Preoperative keratometry values were also obtained using Humphrey Instruments Atlas Version A6 corneal mapping. Achieved refraction was compared with predicted refraction for the two methods of keratometry after the A-constants were optimized to obtain a mean arithmetic error of zero dioptres for each device. The mean absolute prediction error was 0.39 dioptres (standard deviation 0.29) for IOLMaster and 0.48 dioptres (standard deviation 0.31) for corneal mapping (P = 0.0015). Keratometry readings between the devices were highly correlated by Spearman correlation (0.97). The Bland-Altman plot demonstrated close agreement between keratometers, with a bias of 0.0079 dioptres and 95% limits of agreement of -0.48-0.49 dioptres. The IOLMaster was superior to Humphrey Atlas A6 corneal mapping in the prediction of postoperative refraction. This difference could not have been predicted from the keratometry readings alone. When comparing biometry devices, close agreement between readings should not be considered a substitute for actual postoperative refraction data.

Comparison of Preoperative and Postoperative Ocular Biometry in Eyes with Phakic Intraocular Lens Implantations

PurposeTo compare preoperative and postoperative ocular biometry in patients with iris-fixated phakic intraocular lens (pIOLs): Artisan and Artiflex.Materials and MethodsThis study included 40 eyes with Artisan and 36 eyes with Artiflex pIOL implants. Anterior chamber depth (ACD) and axial length (AL) were measured by applanation ultrasonography (A-scan) and partial coherence interferometry (IOLMaster) preoperatively and 3 months after pIOL implantation.ResultsACD measurements after Artisan or Artiflex pIOL implantation were smaller than preoperative measurements. Specifically, the difference after Artisan pIOL implantation was -1.07±0.17 mm by A-scan and -0.08±0.08 mm by IOLMaster. The difference after Artiflex pIOL implantation was -1.31±0.15 mm by A-scan and -0.05±0.07 mm by IOLMaster. After Artisan pIOL implantation, differences in AL measurements by A-scan were insignificant (difference: -0.03±0.15 mm), whereas postoperative AL measurements by IOLMaster were significantly longer than preoperative measurements (difference: 0.12±0.07 mm). After Artiflex pIOL implantation, AL measurements by both A-scan and IOLMaster were significantly longer than preoperative measurements (difference: 0.09±0.16 mm by A-scan and 0.07±0.10 mm by IOLMaster). In the Artiflex group, differences in AL measurements by A-scan correlated with the central thickness of the Artiflex pIOL.ConclusionACD and AL measurements were influenced by iris-fixated phakic IOL implantation.

Biometric measurements in highly myopic eyes

To assess the repeatability and accuracy of optical biometry (Lenstar LS900 optical low-coherence reflectometry [OLCR] and IOLMaster partial coherence interferometry [PCI]) and applanation ultrasound biometry in highly myopic eyes. Division of Preventive Ophthalmology, Zhongshan Ophthalmic Center, Guangzhou, China. Comparative evaluation of diagnostic technology. Biometric measurements were taken in highly myopic subjects with a spherical equivalent (SE) of -6.00 diopters (D) or higher and an axial length (AL) longer than 25.0 mm. Measurements of AL and anterior chamber depth (ACD) obtained by OLCR were compared with those obtained by PCI and applanation A-scan ultrasound. Right eyes were analyzed. Repeatability was evaluated using the coefficient of variation (CoV) and agreement, using Bland-Altman analyses. The mean SE was -11.20 D ± 4.65 (SD). The CoVs for repeated AL measurements using OLCR, PCI, and applanation ultrasound were 0.06%, 0.07%, and 0.20%, respectively. The limits of agreement (LoA) for AL were 0.11 mm between OLCR and PCI, 1.01 mm between OLCR and applanation ultrasound, and 1.03 mm between PCI and ultrasound. The ACD values were 0.29 mm, 0.53 mm, and 0.51 mm, respectively. These repeatability and agreement results were comparable in eyes with extreme myopia (AL ≥ 27.0 mm) or posterior staphyloma. The mean radius of corneal curvature was similar between OLCR and PCI (7.66 ± 0.24 mm versus 7.64 ± 0.25 mm), with an LoA of 0.12 mm. Optical biometry provided more repeatable and precise measurements of biometric parameters, including AL and ACD, than applanation ultrasound biometry in highly myopic eyes. No author has a financial or proprietary interest in any material or method mentioned.

Intraocular Lens Power Measured by Partial Coherence Interferometry

To compare the accuracy of the intraocular lens (IOL) power calculation of the Zeiss IOLMaster versus conventional automated keratometry and contact acoustic biometry after personalized optimization. Three hundred twenty eyes of 249 patients consecutively receiving phacoemulsification and IOL implantation with the sutureless clear cornea approach were enrolled. Preoperative biometry was derived from the Zeiss IOLMaster and an acoustic device (Alcon OcuScan RxP), and keratometry was measured by the Zeiss IOLMaster and a conventional automated keratometer (Topcon KR-8800). One month after surgery, refraction was measured and the predicted refractive errors were calculated with personalized optimization. For eyes responsive to all devices, IOLMaster biometry + IOLMaster keratometry had the best predictability for postoperative refraction, with a mean absolute error (MAE) of 0.38 ± 0.28D, followed by OcuScan RxP biometry + IOLMaster keratometry (MAE, 0.49 ± 0.34D) and OcuScan RxP biometry + KR-8800 keratometry (MAE, 0.54 ± 0.37D) (P < 0.05 for all paired comparisons). For eyes that could not be measured by IOLMaster biometry, the MAE was smaller with IOLMaster keratometry (0.62 ± 0.56D) than with KR-8800 keratometry (0.57 ± 0.52D) (P = 0.03). The variables of age, diabetes mellitus, severity of cataract, axial length, and corneal curvature were unrelated to the predictability of postoperative refraction. The Zeiss IOLMaster yielded more accurate refractive outcomes than the conventional automated keratometry and contact acoustic biometry after personalized optimization. For eyes irresponsive to axial length measurement by the IOLMaster, keratometry of the IOLMaster was still superior to conventional automated keratometry.

Off‐axis partial coherence interferometry in myopes and emmetropes

This study describes the axial and peripheral dimensions of myopic and emmetropic eyes in a wide range of retinal locations using a non-contact optical biometer (Zeiss IOLMaster) based upon the principle of partial coherence interferometry. Understanding the optical properties of the peripheral eye may provide insight into myopia development and the possible effects on off-axis visual performance. Fifty-two myopes (spherical equivalent between -2.00 and -9.62 D) and 27 emmetropes (spherical equivalent between -0.50 and +0.50 D) with astigmatism less than 0.75 D, participated in this study. Axial length and peripheral cornea to retina lengths were measured using partial coherence interferometry at the fovea and up to ± 30° eccentricity along the horizontal and vertical meridian in 10° steps. Relative cornea to retina length was calculated by subtracting the axial length from that obtained at each peripheral location. Our results showed significant differences between refractive groups for both horizontal (p < 0.001) and vertical (p < 0.001) meridians, illustrating that the retinal shape profile is significantly different between myopes and emmetropes. Myopic eyes exhibited a greater rate of change in cornea to retina lengths with increasing eccentricity than emmetropic eyes, with the temporal portion of the retina exhibiting the steepest shift. In addition, significant nasal-temporal asymmetry was observed, which was more pronounced in myopic eyes. Axial and peripheral cornea to retina dimension measurements, using partial coherence interferometry, suggest that myopic eyes tend toward an ellipsoid shape compared to the spherical emmetropic eyes.

Prevalence of corneal astigmatism before cataract surgery in Chinese patients

To assess the demographics and distribution of corneal astigmatism before cataract surgery in Chinese patients. State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China. Clinic-based cross-sectional study. From July 2009 to May 2011, preoperative bilateral partial coherence interferometry (IOLMaster) was performed in consecutive patients having cataract surgery. Patient demographics and keratometric data were recorded. The mean age of the 2849 patients (4831 eyes) was 70.56 years ± 9.55 (SD); there was a predominance of women patients (64.0%). The mean axial length was 23.58 ± 1.13 mm. The mean corneal astigmatism in this cohort was 1.01 D (range 0.05 to 6.59 D). Corneal astigmatism was between 0.25 D and 1.25 D in 67.7% of eyes, 1.25 D or higher in 27.5% eyes, and less than 0.25 D in 4.8% of eyes. Astigmatism was with the rule in 25.1% of eyes, against the rule (ATR) in 58.2% of eyes, and oblique in 16.7% of eyes. The mean steep keratometry measurement was 44.76 ± 1.56 D. Against-the-rule astigmatism increased significantly with older age. Corneal astigmatism largely fell between 0.25 D and 1.25 D in these predominantly elderly female Chinese patients, and ATR astigmatism increased with age. No author has a financial or proprietary interest in any material or method mentioned.

Analysis of corneal astigmatism in cataract surgery candidates at a teaching hospital in Shanghai, China

To describe and quantify the pattern of corneal astigmatism in cataract surgery candidates and to provide information for cataract surgeons and intraocular lens (IOL) manufacturers. Zhongshan Hospital, Fudan University, Shanghai, China. Cross-sectional study. The datasets of cataract surgery candidates acquired between November 1, 2009, and November 30, 2011, were collected and analyzed. Keratometry values were optically measured by partial coherence interferometry (IOLMaster) before cataract extraction. Spearman rank correlation coefficients were used to estimate bivariate correlations. The power vector method, J(0) and J(45) values, and linear regression models were used to assess the association between age and astigmatism. The study evaluated the keratometry values in 1430 eyes (827 patients) with a median age of 75 years (range 16 to 98 years). The corneal astigmatism was 1.00 diopter (D) or higher in 45.45% of eyes. The magnitude of corneal astigmatism was positively correlated with age (ρ = 0.126, P = .000). A trend toward increasing against-the-rule astigmatism with age was found by linear regression models; the per-year increase in age was associated with a J(0) decrease of 0.016 D in right eyes and 0.018 D in left eyes (both P = .000). No association was found between age and J(45). Most eyes having corneal astigmatism of 1.00 D or greater could be covered by the range of the cylindrical power of the toric IOLs available on the market. Against-the-rule corneal astigmatism of relatively younger cataract surgery candidates should be managed more aggressively. No author has a financial or proprietary interest in any material or method mentioned.

Angle Closure in the Namil Study in Central South Korea

To assess the prevalence and associated risk factors of angle closure in a defined population as part of the Namil Study. In this cross-sectional epidemiologic study for residents aged 40 years or older in Namil-myon, a rural area in central South Korea, the examination included slitlamp biomicroscopy, applanation tonometry, gonioscopy, autorefraction, fundus photography, corneal thickness measurement, visual field test with frequency-doubling technology, and anterior chamber depth (ACD) and axial length (AL) measurements with partial coherence interferometry. Standard automated field test and optical coherence tomography or scanning laser polarimetry were performed to confirm the glaucomatous visual field/optic disc damage. Angle closure included primary angle-closure suspect (PACS), primary angle closure (PAC), and primary angle-closure glaucoma (PACG). Definitions of PACS, PAC, and PACG were based on the recommendations from the International Society for Geographical &Epidemiological Ophthalmology. Among the 1426 individuals enrolled for the assessment, with exclusion of cataract surgery, the prevalence rates of PACS, PAC, PACG, and overall angle closure in at least 1 eye were 2.0% (95% CI, 1.3%-2.8%), 0.5% (95% CI, 0.1%-0.9%), 0.7% (95% CI, 0.3%-1.1%), and 3.2% (95% CI, 2.3%-4.2%), respectively. Multivariate analysis found that older age (odds ratio [OR], 1.8797; 95% CI, 1.4624-2.4162), shallower ACD (OR, 0.9982; 95% CI, 0.9977-0.9987), and shorter AL (OR 0.9978; 95% CI, 0.9969-0.9988) (P < .001 for each) were significantly associated with angle closure. The overall prevalence of angle closure was 3.2% in the present study. On the basis of these findings, increasing age, shallower ACD, and shorter AL appear to be associated with angle closure. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00727168.