Lenstar LS Research Articles

Peripheral vitreochorioretinal dystrophy in patients with various types of myopia

Background. Over the past decade, there has been an in¬crease in myopia prevalence in the world; in many countries it is considered as epidemic. In case of an unfavorable course, myopia becomes the cause of retinal pathology, which in se¬vere cases leads to an irreversible decrease in corrected visu¬al acuity and to visual impairment that occurs at working age. Purpose. To analyze the relationship between the occurrence of peripheral vitreochorioretinal dystrophy (PVCD) in patients with myopia depending on its type: refractive and axial. Material and methods. A retrospective cohort analysis involved 304 patients (608 eyes) of 13 to 70 years old with acquired myopia: mild (19.40%), moderate (42.93%) and high (37.67%). In all cases, myopia was complicated by PVCD. All patients were divided into 2 groups according to the type of myopia: refractive and axial myopia. Biometric data (LENSTAR LS 900) and keratometry (“Huvitz”, South Korea) were used as criteria for patient selection. Results. The distribution of patients showed that PVCD most often occurs in the group of patients with axial myopia of moderate (44.48%) and high (39.70%) degrees. In the group of patients with mild axial myopia, the incidence was 15.80%. A clear correlation was noted between the development of PVCD and the axial elongation. In contrast, in patients with refractive myopia, the incidence of PVCD was two times higher in case of mild myopia (50.00%) than in cases of moderate (29.69%) and high myopia (20.31%) put together. Conclusion. The study revealed that PVCD is almost 8,5 times more likely to occur in case of axial myopia than in case of refractive myopia. A possible cause of PVCD development in case of axial myopia is an increase in the axial length, while in case of refractive myopia its possible cause is the increase in the eyeball’s transverse size. Regardless of the type of myopia and its degree, the study of the periphery of the retina is an essential element of diagnostics for timely detection of PVCD and monitoring the progression of axial myopia is an important criterion for its prevention.

The Effect of Pharmacological Dilation on Calculation of Targeted and Ideal IOL Power Using Multivariable Formulas.

BackgroundTo examine the effect of pharmacologic dilation on biometric parameters measured by the Lenstar LS 900, and whether these changes affect the power of the calculated intraocular lens (IOL) using multivariable formulas in an undilated versus pharmacologically dilated state.MethodsProspective study of 98 phakic eyes from 53 patients. Axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), and keratometry (K) readings were measured. The first set of measurements was taken prior to dilation. After dilation (pupil diameter ≥ 6.0 mm), a second set of measurements was taken. The Barrett, Olsen, Hill-RBF, Haigis, SRK/T, and Holladay I formulas were used to calculate IOL power before and after dilation. Two calculation methods were used: method A used a commonly available IOL targeted to achieve the lowest myopic spheroequivalent residual refraction; method B calculated ideal IOL power for emmetropia.ResultsStatistically significant increases were seen in CCT (p < 0.01), ACD (p < 0.01), and AL (p < 0.01) whereas a statistically significant decrease was seen in LT (p < 0.01) post dilation. Using method A, the percentage of eyes which would have received an IOL with 0.5 D or 1.0 D of higher power, if post-dilation measurements were used, were 25.5%, 30.6%, 20.4%, and 23.5% for Barrett, Olsen, Hill-RBF, and Haigis, respectively. Using method B, only Haigis and Olsen had a statistically significant increase in ideal IOL power.ConclusionsPharmacologic dilation can be associated with an increase in non-custom IOL dioptric power when using multivariable formulas, which may lead to a myopic surprise.

Evaluation of biometric parameters in phacomorphic glaucoma and mature cataracts.

The aims of this study were to compare the biometric parameters and axial lengths of eyes with phacomorphic glaucoma and mature cataract and to identify differences that might predispose to development of phacomorphic glaucoma. Three hundred forty-two patients were enrolled in this retrospective study. The eyes were divided into four groups-Group (G)1: phacomorphic glaucoma (n = 29), G2: mature cataract (n = 313), G3: contralateral phacomorphic glaucoma (n = 29), and G4: contralateral mature cataract (n = 313). Central corneal thickness and anterior chamber depth were assessed by optical low-coherence reflectometry (Lenstar LS 900®; Haag-Streit AG, Switzerland), while axial length was determined by A-scan ultrasound biometry. The mean central corneal thickness of G1 was significantly higher than in other groups (p < 0.001) and the mean anterior chamber depth of G1 was the lowest among the groups (p < 0.001). Also, G2 had lower mean anterior chamber depth than G4 (p < 0.001) and G3 had lower mean anterior chamber depth than G4 (p = 0.007). Anterior chamber depth less than 3.27 mm had the higher odds ratio for distinguishing G3 versus G4 (odds ratio = 10.79, p < 0.001). Furthermore, patients aged ⩾68.9 years had the higher odds ratio for distinguishing G1 versus G2 (odds ratio = 2.82, p = 0.019). There was no significant difference in the presence of pseudoexfoliation material between G1 and G2 (p = 0.057). There were no significant differences in axial length values among the four groups (p = 0.097). Advanced age and shallow anterior chamber depth were found to be risk factors for developing phacomorphic glaucoma, but the presence of pseudoexfoliation material was not found to play a role as a risk factor in phacomorphic glaucoma development.

Accuracy of two devices and three different calculation methods for predicting residual astigmatism after intraocular lens implantation

This study examined how different methods of biometric measurement, types of intraocular lens calculation, and levels of surgeon experience affected predicted postoperative astigmatism with toric intraocular lens implantation. The error in predicted residual astigmatism was determined using the IOL Master 500 and Lenstar LS 900 devices and was calculated by the Alcon toric calculator, Alcon toric calculator with Baylor nomogram, and Barrett toric calculator. Results were reviewed from 147 eyes of 125 patients. Of the three calculations, the Barrett toric calculator had the lowest mean absolute error in predicted residual astigmatism (P < 0.0001). The mean absolute errors of the IOL Master 500 and the Lenstar LS 900 were not significantly different when compared using three different calculation methods (P = 0.54). The mean absolute error was significantly lower (P = 0.049) for ophthalmology staff than for ophthalmology residents when calculation methods were considered. In conclusion, the calculation method used for IOL selection in cataract surgery significantly affects the accuracy of both staff and residents.

Estimation of angle kappa and pupil barycentre configuration in myopic tilted disc syndrome

BackgroundTo evaluate the angle kappa and pupil barycentre configuration in patients with myopic tilted disc syndrome (TDS).MethodsThirty‐five eyes of 35 patients with TDS were included in the study. Thirty‐five eyes of 35 age‐ and sex‐matched healthy subjects were enrolled in the control group. All measurements were performed with the Lenstar LS 900. Angle kappa was calculated according to Pythagorean theorem using the x and y co‐ordinates of the pupil centre. Pupil dx and pupil dy values (pupil dx: x co‐ordinate of pupil centre relative to corneal apex, pupil dy: y co‐ordinate of pupil centre relative to corneal apex) were used to evaluate the pupil barycentre configuration. Central corneal thickness, white to white (cornea diameter), pupil diameter, anterior chamber depth, lens thickness, and axial length were also measured.ResultsThe calculated mean angle kappa distance was 0.27 ± 0.15-mm in the TDS group and 0.29 ± 0.23-mm in the control group (p = 0.42). The mean pupil dx was −0.01 ± 0.24-mm in the TDS group and −0.17 ± 0.14-mm in the control group (p = 0.006). The mean pupil dy was −0.02 ± 0.13-mm in the TDS group and −0.05 ± 0.22-mm in the control group (p = 0.65).ConclusionsThe pupil barycentre in TDS cases was statistically significantly closer to the corneal vertex on the horizontal plane compared to the control group. However, there was no statistically significant differences in terms of angle kappa and pupil dy values between the groups. According to our results, refractive surgery can be performed safely with respect to complications related to decentration of ablation zone and decentration of multifocal intraocular lenses in these groups of patients.

Comparison of Preoperative Parameter Measurements Using an Optical Biometer, Automated Keratometer, and a Placido-Based Topographer Module

To assess the agreement of corneal power, corneal astigmatism, axis location, and astigmatic vector component measurements using a Lenstar LS900, a T-cone add-on, and an ARK 1S autorefractor, furthermore, to assess instrument agreement in a subset of astigmatic eyes. Retrospective analysis of keratometric readings from 3 instruments for 66 eyes undergoing cataract surgery at the Maryland Veterans Affairs Medical Center from November 2014 to 2015. Agreement in corneal power, mean corneal power, axis location, and astigmatic vector components (J0, J45) between devices was evaluated. Comparability was assessed using intraclass correlation, analysis of variance (ANOVA) one-way analysis, Bland-Altman analysis, and power vector analysis. Intraclass correlation was then assessed for a subset of 42 eyes with corneal astigmatism greater than or equal to 1 D. The intraclass correlation between instruments was 0.941 for corneal power, 0.788 for corneal astigmatism, 0.932 for J0, and 0.809 for J45. The ANOVA one-way repeated P values comparing Kf, Ks, Km, corneal astigmatism, axis location, J0, and J45 were all greater than 0.05. Power vector analysis showed nearly all values between instruments to be within ±0.5 D. Finally, the intraclass correlation between instruments in eyes with ≥1 D of corneal astigmatism as measured by the T-cone was 0.946 for corneal power, 0.837 for corneal astigmatism, 0.948 for J0, and 0.950 for J45. The high level of agreement between all devices indicates the instruments may be used interchangeably. Our data suggest that this may also be true for the subset of eyes with greater than or equal to 1 D in astigmatism, highlighting the toric intraocular lens population.

Algorithm for predicting axial displacement of the optic part of IOL after phacoemulsification

To test a prediction algorithm for deflection of the optical part of IOL after uncomplicated phacoemulsification. The study included 226 patients (287 eyes) who underwent phacoemulsification with implantation of intracapsular AcrySof IOL. Preoperative examination included IOLMaster, Lenstar LS 900 biometry and Pentacam HR keratotopography. All measurement were repeated one month postoperatively. To determine the tilt and deflection of the IOL's optical part, anterior segment optical coherence tomography (OCT) was performed on Topcon 3DOCT-2000. OCT data analysis helps identify the slope and deflection of the IOL's optical part relative to the pupil plane. In the previous study we built logistic regression models for predicting the deflection of the IOL's optical part with high predictive quality based on the calculated IOL power and preoperative biometry measurements. When checked with new patient data, the areas under the ROC curves have changed slightly. Large area under the ROC curves with small deviation rates, as well as retention of the level of true positive responses with little increase in false negative responses verify the high quality of the models. Logistic regression models based on the optical power of the implanted IOL, as well as on a combination of preoperative biometry data from IOLMaster and Lenstar LS 900, make it possible to predict the probability of deflection of the optical part of IOL with high reliability and promptly correct the IOL power.

Verion digital marking versus smartphone-assisted manual marking and isolated manual marking in toric intraocular lens implantation

Purpose:To compare the accuracy of isolated manual marking and smartphone-assisted manual marking with the Verion image-guided system for toric intraocular lens (IOL) implantation.Methods:In this prospective observational study, 42 eyes of 36 patients planned for phacoemulsification with toric IOL implantation with corneal astigmatism >1D as measured on Lenstar LS 900 optical biometer were included. Patients were preoperatively registered and photographed on the Verion image-guided system. In the operating room, the patient's eye was manually marked at the 6 o′ clock limbus (Manual axis-90°) on slit-lamp in sitting position. Next, using the smartphone android app—iToric Patwardhan, the exact mark axis was confirmed (Smartphone axis). Following this, the patient was taken on the operation table where the mark axis was confirmed with Verion digital overlay on an external screen (Verion axis). The absolute angular deviation of manual axis from Verion was compared with the absolute angular deviation of the smartphone axis from Verion as the primary outcome measure.Results:The mean absolute angular deviation between the smartphone axis and the Verion axis was 2.62°, which was significantly lower (P < 0.05) than that between the manual axis and Verion axis (4.60°). Moreover, the intraclass correlation coefficient between the smartphone axis and Verion axis was 0.88 indicating a strong agreement between the two.Conclusion:Smartphone-assisted manual marking significantly improves the accuracy of manual marking alone when comparing with the Verion Digital Marker system for toric IOL implantation.

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.

Repeatability and reproducibility of optical biometry implemented in a new optical coherence tomographer and comparison with a optical low-coherence reflectometer

To examine the repeatability and reproducibility of biometry provided by a new anterior-posterior segment spectral-domain optical coherence tomography (SD-OCT) device (Revo NX) and compare it with that provided by a validated optical low-coherence reflectometry (OLCR) biometer (Lenstar LS 900). Hygeia Clinic, Gdańsk, Poland. Prospective evaluation of diagnostic test. The axial length (AL), lens thickness (LT), central corneal thickness (CCT), and anterior chamber depth (ACD) (corneal epithelium to lens) were measured in eyes of volunteers. Two skilled operators obtained 3 measurements in random order with the SD-OCT device. Repeatability was calculated for each observer, while reproducibility was assessed by a change in observer. To compare agreement between the SD-OCT device and OLCR device, the first observer took 3 measurements with both devices. The study evaluated 63 eyes of 63 volunteers. The mean AL measurement (+0.11mm±0.02 [SD]) and mean ACD measurement (0.05±0.04mm) were significantly higher with the SD-OCT device than with the OLCR device; the CCT measurements did not differ between the devices. A very strong correlation was found for all parameters, while Bland-Altman analysis showed narrow 95% limits of agreement for AL (0.06 to 0.15mm), ACD (-0.02 to 0.12mm), LT (-0.23 to 0.17mm), and CCT (-7.83 to 6.17μm). The new SD-OCT device provided repeatable and reproducible AL, ACD, LT, and CCT measurements. The results with the SD-OCT device showed strong correlations with those obtained with the OLCR device. However, the AL and ACD measurements of the 2 devices cannot be considered interchangeable.

Effect of congenital blepharoptosis on corneal biomechanical properties and changes after ptosis surgery.

We studied the difference in the corneal biomechanical parameters of ptotic and fellow eyes in patients with congenital blepharoptosis. The correlations between corneal biomechanical parameters and demographic or ocular parameters, and the changes after surgery were also researched. The corneal biomechanical parameters were measured by Corvis ST tonometry. The central corneal thickness (CCT), axial length (AL) and keratometry measurements were performed with LenStar LS900, and intraocular pressure (IOP) by non-contact applanation tonometry. The parameters were evaluated for the effect of ptosis and the relationship of corneal biomechanical parameters. These examinations were repeated 6 months after blepharoptosis surgery. Twenty-nine patients were enroled. The Corvis ST parameters (Deformation amplitude [DA], A1 times, and A1 velocity), CCT, IOP with NCT, IOP with corrected, differed significantly between ptotic and fellow eyes. CCT was significantly positively correlated with Length A1 and IOP with Corvis, and negatively correlated with IOP corrected by Corvis of the ptotic eyes. The same tendency was found in the fellow eyes. Six months after the ptosis surgery, the differences in corneal biomechanics parameters between ptotic eyes and fellow eyes were not significantly changed. Congenital blepharoptosis causes significant corneal biomechanical changes measured by Corvis ST. The ptotic eyes had thicker and less deformable corneas. The differences in corneal biomechanics between ptotic eyes and fellow eyes were mostly related to CCT changes. Six months after surgery, these differences in corneal biomechanics did not change significantly.

Predictive value of intracrystalline interphase point measured by optical low-coherence reflectometry for the estimation of the anatomical position of an intraocular lens after cataract surgery

To investigate the predictive value of the intracrystalline interphase point (ICIP) measured with optical low-coherence reflectometry (OCLR) to estimate the final lens position (FLP) of an intraocular lens (IOL) after cataract surgery. Alcañiz Hospital, Teruel, Spain. Single-center retrospective descriptive study. Patients undergoing cataract surgery were enrolled. They were grouped according to the IOL implanted as follows: Group 1, Acrysof IQ aspheric SN60WF IOL (77 eyes); Group 2, enVista MX60 IOL (71 eyes); Group 3, CT Asphina 409 IOL (44 eyes). An OCLR-based biometer (Lenstar LS 900 system) was used for biometric measurements preoperatively and at 4 to 5weeks postoperatively. The study comprised 192 eyes of 174 patients (mean age: 76.4years). One hundred seventy eyes (88.5%) eyes showed an absolute refractive prediction error (ARPE) less than 0.50 diopters (D). The mean ARPE was 0.25 D ± 0.21 (SD). Significantly higher FLP values were found in Group 2 compared with the other two groups (P<.001). Significantly lower ICIP values were found in the eyes with an ARPE of 0.50 D or more compared with eyes that had an ARPE less than 0.50 D in Group 1 (P=.042) and Group 2 (P=.023). The correlation of the FLP with the ICIP was good in all three groups (r≥0.74, P <.001). Three linear expressions were obtained to predict the FLP from the ICIP and other preoperative data (R2: 0.85, 0.69, and 0.49 in Groups 1, 2, and 3, respectively). The position of the ICIP measured with OCLR correlated with the FLP after cataract surgery, and it can be used to optimize IOL power calculations.

Distribution and related factors of corneal regularity and posterior corneal astigmatism in cataract patients.

PurposeTo study the distribution of posterior corneal astigmatism (PCA) and its influencing factors in Chinese patients before cataract surgery.Patients and methodsA retrospective study was conducted in the First Affiliated Hospital of Soochow University, Suzhou, China. In all, this study enrolled 121 eligible eyes of 121 cataract patients. The astigmatism, aberrations and Q value of anterior, posterior and total cornea and anterior segment parameters (ACD, CCT, WTW, ATA) were measured by the Sirius System, and AL was measured by Lenstar LS 900. Cataract was diagnosed using slit-lamp examination.ResultsThe mean age of patients was 67.44±10.66 years old. Mean PCA was 0.31±0.17 (range 0.05–1.09) D and 85.9% eyes had PCA values <0.5 D. With-the-rule (WTR) astigmatism predominated the anterior cornea astigmatism (ACA) (48.8%) and total corneal astigmatism (TCA) (61.2%), while against-the-rule (ATR) astigmatism predominated posterior (86.0%). Significant positive correlation was found between the astigmatic power vector (APV) of ACA and PCA (Pearson correlation=0.318, P<0.001); TCA and PCA (Pearson correlation=0.204, P=0.025); keratometric astigmatism and PCA (Pearson correlation=0.356, P<0.001); this study also found a positive correlation between primary spherical aberration (Z4°) of the total cornea and PCA (Pearson correlation=0.266, P=0.003); primary spherical aberration (Z4°) of the corneal front surface and PCA (Pearson correlation=0.260, P=0.004); total corneal aberrations (Total cornea root mean square [RMS]) and PCA (Pearson correlation=0.327, P<0.001); total corneal higher-order aberrations (Total HOA RMS) (Pearson correlation=0.232, P=0.011); total corneal lower-order aberrations (Total LOA RMS) (Pearson correlation=0.250, P=0.006). A positive linear correlation between Q value of corneal front surface and PCA, either 6 mm pupil diameter (Pearson correlation=0.264, P=0.003) or 8 mm pupil diameter (Pearson correlation=0.184, P=0.043) was found in this study.ConclusionCorneal aberration, Q value (front surface specifically) was essential that we need to take into consideration when we conduct PCA and intraocular lens measurement in clinics.

Сравнительная оценка измерений оптических биометров IOLMaster 700 и LENSTAR LS 900

Сравнительная оценка измерений оптических биометров IOLMaster 700 и LENSTAR LS 900

Central Corneal Thickness and Its Association with Birth Parameters in Chinese Adolescents

ABSTRACT Purpose To examine the distribution and determinants of central corneal thickness (CCT) including birth weight and gestational age in a school-based samples of Grade 7 students in rural China. Methods 2346 (93.5%) grade 7 students with a mean age of 13.8 years participated in the study. CCT was measured for both eyes using the LenStar LS900. Information regarding birth weight and gestational age was retrieved from the participants’ delivery records. A linear regression model was established to examine the relationship of birth weight, gestational age and other factors with CCT. Results The mean CCT in this population was 534.7 µm and boys had a greater CCT compared with girls (P = .06). CCT was positively related to axial length (r = 0.056) while negatively related to anterior chamber depth (r = −0.076) and corneal power (r = −0.105) . In multivariate analyses, the cornea was 19.35µm thinner in individuals with low birth weight compared with those with normal. In addition, the cornea was 25.25µm thinner in prematurely born adolescents compared with full-term ones. The combined effect of birth weight and gestational age on CCT was not statistically significant (P for interaction = 0.12) Conclusions Low birth weight and small gestational age are associated with thinner corneas in adolescence. This disparity across groups with different levels of birth parameters should be taken into account by future studies investigating CCT as risk factors or diagnostic tests for glaucoma.

The acute effects of single cup of coffee on ocular biometric parameters in healthy subjects

PurposeTo evaluate ocular biometric changes in healthy subjects after caffeine consumption from a cup of coffee. MethodsA total of 36 subjects were included in this prospective observational study. Axial length (AL) and anterior segment parameters including aqueous depth (AD), anterior chamber depth (ACD), lens thickness (LT), and central corneal thickness (CCT) were measured with optic biometry, Lenstar LS 900 (Haag-Streit, Inc., Koeniz, Switzerland) before and 1 and 4 h after ingesting a cup of coffee (60 mg caffeine/100 mL). ResultsMean age of the participants was 30.05 ± 7.43 years (range, 19–45). At baseline, 1st, and 4th hour, AL values were 23.9 ± 1.04 mm, 23.91 ± 1.04 mm, and 23.89 ± 1.04 mm, respectively, and no significant difference was observed (P>0.05). At baseline, 1st, and 4th hour, AD values were 3.06 ± 0.3 mm, 3.11 ± 0.3 mm, and 3.09 ± 0.3 mm, and ACD values were 3.6 ± 0.32, 3.66 ± 0.31, and 3.64 ± 0.31, respectively. AD and ACD values were significantly greater than baseline at 1st and 4th hours following coffee ingestion. Coffee intake caused a significant reduction in LT, compared with baseline and at the 1st and 4th hours which were 3.76 ± 0.28 mm, 3.69 ± 0.32 mm, and 3.72 ± 0.27 mm, respectively. No statistically significant difference was determined in between the 3 measurements in terms of CCT (P>0.05). ConclusionCaffeine causes a significant increase in AD and ACD and a significant decrease in LT following oral intake, for at least 4 h.

Keratometry in children: Comparison between auto-refractokeratometer, rotating scheimpflug imaging, and biograph

PurposeTo determine the agreement and validity of keratometric measurements in children with the Nidek ARK-510A auto-refractokeratometer compared to rotating Scheimpflug imaging with Pentacam and biograph with Lenstar LS 900. MethodsThis study was conducted on 5620 schoolchildren aged 6–12 years in Shahroud, Iran. Minimum and maximum keratometry values and corneal astigmatism magnitude were compared by calculation of Paired difference, interclass correlation coefficient, and 95% limits of agreement (LoA) between devices. ResultsAfter applying the exclusion criteria, 4215 right eyes were enrolled into the study. Mean minimum keratometry with Nidek ARK-510A, Pentacam, and Lenstar was 43.13±1.51, 43.14±1.48, and 42.87±1.46 diopters (D), respectively, and mean maximum keratometry was 43.97±1.59, 44.00±1.56, and 43.75±1.54D, respectively. Nidek ARK-510A overestimated minimum and maximum keratometry by 0.25±0.37 and 0.22±0.41, respectively, compared to Penatcam. The LoA between Nidek ARK-510A and Pentacam for minimum and maximum keratometry measurements were −0.98 to 0.47D and −1.02 to 0.57D, respectively. The LoA between Nidek ARK-510A and Lenstar for minimum and maximum keratometry measurements were −0.70 to 0.72D and −0.79 to 0.85D, respectively. The agreement between devices was best in emmetropes, worst in hyperopes. For astigmatic vector components, the agreements between devices were poor but best agreement was between Nidek ARK-510A and Pentacam. ConclusionsKeratometry measurement with Nidek ARK-510A was not significantly different from Pentacam and Lenstar, and this device can be used in screening programs in emmetropes.

The influence of two calculation methods on the outcomes of Toric intraocular lenses

Objective: To evaluate the influence of Barrett calculator and AcrySof calculator on astigmatism correction effect. Methods: This is a randomized prospective study. A total of 64 cases (81 eyes) who planed to undergo phacoemulsification at Tianjin Medical University Eye Hospital during January 2017 and March 2018 were enrolled and divided into two groups randomly, including of the Barrett calculator group of 34 cases (41 eyes) and the AcrySof calculator group of 30 cases (40 eyes). Preoperative ocular biological parameters were measured using Lenstar LS900. The Toric intraocular lenses (IOL) plans were determined based on Barrett calculator and the AcrySof calculator for the two groups respectively. Subjective optometry was performed by phoropter and Toric IOL alignment was detected by slitlamp examination at 1 and 3 months postoperatively. Statistical analysis was taken with the data of 29 cases (35 eyes) in the Barrett calculator group and 26 cases (35 eyes) in the AcrySof calculator group, there were 20 males (25 eyes) and 35 females (45 eyes) with an average age of (72±10) years. The difference between the predicted residual astigmatism by the two calculators and the residual astigmatism obtained by postoperative optometry is the error of refractive astigmatism (ERA). The magnitude error is the algebraic difference of ERA. Vector error(VE) is a vector difference of ERA. Statistical analysis of magnitude error and VE between the two groups were taken by student's t test or rank sum test. Results: At 1 months and 3 months, the magnitude error absolute value of Barrett calculator group were (0.19±0.16)D, (0.28±0.24)D, and those of AcrySof calculator group were (0.36±0.28)D, (0.46±0.41)D, and the differences were statistically significant (t=-3.050, -2.036, both P<0.05). At 1 month postoperatively, the overall, with-the-rule astigmatism, and against-the-rule astigmatism VE of the Barrett calculator group were (0.30±0.21)D, (0.26±0.22)D, (0.37±0.26)D respectively, and those of the AcrySof calculator group were (0.47±0.33)D, (0.51±0.34)D and (0.52±0.38)D respectively, the differences between the two groups were statistically significant (t=-2.533, -2.436, -2.150, all P<0.05). At 3 months postoperatively, the overall, with-the-rule astigmatism, and against-the-rule astigmatism VE of the Barrett calculator group were (0.37±0.28)D, (0.29±0.17)D, (0.35±0.27)D respectively, and those of the AcrySof calculator group were (0.59±0.46)D, (0.54±0.37)D, (0.64±0.52)D respectively, the differences between the two groups were statistically significant (t=-2.142, -2.038, -2.481, all P<0.05).The difference of X(EV) between the Barrett calculator group and the AcrySof calculator group was statistically significant[-0.13(-0.36-0.80)D vs. 0.19(-1.01-0.71)D, Z=-2.965,P<0.01], and the difference of Y(EV) was statistically significant [-0.02(-0.51-0.64)D vs. -0.15(-0.88-1.10)D, Z=-2.076, P<0.05] at 1 months. There was no significant difference in X(EV) and Y(EV) (both P>0.05) at 3 months. Conelusion: As compared to AcrySof Toric calculator, the application of Barrett calculator in selecting Toric IOL may reduce ERA and improve Toric IOL correction outcomes. (Chin J Ophthalmol, 2019, 55:208-213).

Approximating sum-of-segments axial length from a traditional optical low-coherence reflectometry measurement

To present the Cooke-modified axial length (CMALInitial) method, which closely approximates sum-of-segments AL. Notably, sum-of-segments AL has been shown to improve predictions of many intraocular lens (IOL) power formulas; however, calculating this AL requires information that is not readily available. Comparative case series. Distinct datasets of 215 eyes and 1442 eyes, which were measured before cataract surgery with a commercially available optical biometer (Lenstar LS 900), were identified. The AL measured by this machine was labeled "traditional AL." Prediction Error. The CMALInitial, sum-of-segments AL, and traditional AL methods with Bland-Altman plots and r2 values were compared, along with graphs of prediction errors. The CMALInitial was developed from 215 eyes and evaluated in the 1422-eye validation dataset. The r2 for CMALInitial versus the sum-of-segments AL was 0.99983. The predictions based on CMALInitial were compared with those based on traditional AL using the Hoffer Q, Holladay 1, SRK/T, and Holladay 2 IOL formulas. The CMALInitial produced more accurate predictions in all four formulas (P<.001). Eyes in all datasets were then combined to create the final recommendation: CMALFinal=1.23853+0.95855×traditional AL - 0.05467× lens thickness (all measurements in millimeters). A modified AL method (CMAL) was easy to calculate. Using CMAL improved predictions for at least four IOL power prediction formulas, especially at extreme ALs. Caution is advised if using CMAL with other formulas.

An Evaluation of the IOLMaster 700.

To evaluate the repeatability and reproducibility of the Carl Zeiss Meditec IOLMaster 700, which uses swept-source optical coherence tomography technology, along with its agreement with the IOLMaster 500 and Lenstar LS 900. In a clinical practice, complete measurements were taken on one eye of 100 subjects: 51 with cataracts and 49 with clear lenses. Three sets of measurements were taken by 3 operators with three different IOLMaster 700 units, and one operator took 3 measurements with the IOLMaster 500 and the Lenstar. A random-effects model of analysis of variance was used to estimate the repeatability and reproducibility. The 95% limits of agreement (95% LoA) were calculated for all comparisons. Comparing the IOLMaster 700 and IOLMaster 500 in cataract patients, 95% LoA were -0.01 to +0.06 mm for axial length, -0.44 to +0.27 D for corneal power, and -0.18 to +0.17 mm for anterior chamber depth. Comparing the IOLMaster 700 and Lenstar for corneal thickness and lens thickness yielded 95% LoA of -4 to +13 μm and -0.26 to +0.41 mm, respectively. The repeatability and reproducibility limits for the IOLMaster 700 were ±0.014 and ±0.023 mm for axial length; ±0.26 and ±0.27 D for corneal power; ±7 and ±11 μm for corneal thickness; ±0.02 and ±0.02 mm for anterior chamber depth; and ±0.02 and ±0.05 mm for lens thickness, respectively. There was good agreement between the IOLMaster 700 and comparator instruments and superior or equivalent precision. Some differences were noted, but not considered clinically meaningful.