Meta-analysis of optical low-coherence reflectometry versus partial coherence interferometry biometry

Addition by Subtraction: Reversing Epikeratophakia and Stromal Scarring in a Patient With Myopia Magna

PURPOSE

To describe a three-phase surgical approach for managing progressive visual decline in a patient with myopia magna and a history of epikeratophakia.

METHODS

A 55-year-old woman with previous epikeratophakia surgery in both eyes experienced progressive visual deterioration. The three-phase approach included: (1) removal of the epikeratophakia lenticule, (2) cataract extraction with intraocular lens implantation, and (3) transepithelial topography-guided photorefractive keratectomy (trans-PRK). Preoperative and postoperative refraction, corneal topography, and visual acuity were assessed.

RESULTS

After trans-PRK, the right eye exhibited regularization of the corneal surface, with a final best spectacle-corrected acuity of 0.15 logMAR. A similar two-phase approach without lenticule removal was applied to the left eye, resulting in improved visual outcomes.

CONCLUSIONS

A three-phase surgical approach combining lenticule removal, cataract surgery, and topography-guided PRK offers a potential pathway for visual improvement in patients with phakic postepikeratophakia.

Comparative analysis of a novel spectral-domain OCT biometer versus swept-source OCT or OLCR biometer in healthy pediatric ocular biometry

With the advancements in ocular biometric technology, there have been significant improvements in accurately and efficiently measuring ocular parameters. The aim of this study is to compare the reliability of biometric parameters obtained using a new frequency-domain optical coherence tomography (SD-OCT) biometer with the measurements obtained from swept-source OCT (SS-OCT) and optical low coherence reflectometry (OLCR) biometers. This study employed an observational cross-sectional design. Measurements of axial length (AL), flat and steep corneal keratometry (K1 and K2), and central corneal thickness (CCT) obtained using the The Colombo IOL were compared with those obtained with the IOLMaster 700 and SW-9000 devices. The agreement were evaluated using intraclass correlation coefficient (ICC) and Bland-Altman analyses. The differences of the measurements of the three increments were assessed by one-way ANONA. 73 right eyes of 73 healthy pediatric subjects were analyzed. The AL difference measured by Colombo IOL compared with IOLmaster700 and SW-9000 were 0.00 ± 0.02 mm and - 0.07 ± 0.05 mm, respectively (P > 0.05, ANOVA). There was no statistically significant difference in CCT, K1, and K2 among the three instruments (all P > 0.05, ANOVA). The ICC values for AL, K1, K2, and CCT were 0.999, 0.996, 0.995, and 0.998, respectively. The Bland-Altman analysis showed an agreement of AL, K1, K2, and CCT with Colombo IOL and IOLMaster 700 spanned over 0.08 mm, 0.71D, 0.69D, and 12.17 μm, respectively. The agreement of AL, K1, K2, and CCT with Colombo IOL and SW-9000 spanned approximate 0.21 mm, 0.75D, 1.06D, and 14.37 μm, respectively. The new SD-OCT biometer and the SS-OCT biometer showed strong agreement in measuring AL and CCT in healthy pediatric subjects. This supports the reliability of the new SD-OCT biometer as an alternative for assessing these parameters. However, K1 and K2 could not be used interchangeably in clinical practice. Further research is needed to explore their applicability in different clinical settings and patient populations."light" />.

Ocular Biometric Components in Hyperopic Children and a Machine Learning-Based Model to Predict Axial Length

Purpose

The purpose of this study was to investigate the development of optical biometric components in children with hyperopia, and apply a machine-learning model to predict axial length.

Methods

Children with hyperopia (+1 diopters [D] to +10 D) in 3 age groups: 3 to 5 years (n = 74), 6 to 8 years (n = 102), and 9 to 11 years (n = 36) were included. Axial length, anterior chamber depth, lens thickness, central corneal thickness, and corneal power were measured; all participants had cycloplegic refraction within 6 months. Spherical equivalent (SEQ) was calculated. A mixed-effects model was used to compare sex and age groups and adjust for interocular correlation. A classification and regression tree (CART) analysis was used to predict axial length and compared with the linear regression.

Results

Mean SEQ for all 3 age groups were similar but the 9 to 11 year old group had 0.49 D less hyperopia than the 3 to 5 year old group (P < 0.001). With the exception of corneal thickness, all other ocular components had a significant sex difference (P < 0.05). The 3 to 5 year group had significantly shorter axial length and anterior chamber depth and higher corneal power than older groups (P < 0.001). Using SEQ, age, and sex, axial length can be predicted with a CART model, resulting in lower mean absolute error of 0.60 than the linear regression model (0.76).

Conclusions

Despite similar values of refractive errors, ocular biometric parameters changed with age in hyperopic children, whereby axial length growth is offset by reductions in corneal power.

Translational Relevance

We provide references for optical components in children with hyperopia, and a machine-learning model for convenient axial length estimation based on SEQ, age, and sex.

Influence and predictive value of optional parameters in new-generation intraocular lens formulas

PURPOSE

To evaluate the accuracy of various variations of new-generation multivariate intraocular lens (IOL) power calculation using the Barrett Universal II, Castrop, Emmetropia Verifying Optical 2.0, Hill-Radial Basis Function 3.0, Kane, and PEARL-DGS formulas with and without optional biometric parameters.

SETTING

Tertiary care academic medical center.

DESIGN

Retrospective case series. Single-center study.

METHODS

Inclusion of patients after uneventful cataract surgery implanting AU00T0 IOLs. Data from one eye per patient were randomly included. Eyes with a corrected distance visual acuity worse than 0.1 logMAR were excluded. IOLCON-optimized constants were used for all formulas other than the Castrop formula. The outcome measures were prediction error (PE) and absolute prediction error (absPE) for the 6 study formulas.

RESULTS

251 eyes from 251 patients were assessed. Excluding lens thickness led to statistically significant differences in absPE in several formulas. Leaving out horizontal corneal diameter did not impact absPE in several formulas. Differences in PE offset were observed between the various formula variations.

CONCLUSIONS

When using multivariate formulas with an A-constant, including certain optional parameters is vital for optimal refractive results. Formula variations excluding certain biometric parameters need specifically optimized constants and do not perform similarly when using the constant of the respective formula using all parameters.

Lenstar LS900 vs EchoScan US-800: comparison between optical and ultrasound biometry with and without contact lenses and its relationship with other biometric parameters

BACKGROUND

Due to the increasing use of contact lenses (CL) and the interest in ocular and body size relationships, this study aimed to compare measurements from two biometers (contact ultrasonic EchoScan US-800 and non-contact optical Lenstar LS900) with and without CL and to explore the relationship between ocular and body biometric parameters.

DESIGN AND METHODS

This cross-sectional study measured ocular biometry using two biometers along with their body height and right foot length in 50 participants. Differences between biometry data from the two devices were compared and correlations between ocular and body biometric values were analyzed.

RESULTS

All parameters showed interbiometric differences (p ≤ 0.030), except crystalline lens thickness during CL wear (p = 0.159). Comparing measurements with and without CL, differences were observed in axial length (p < 0.001), vitreous length measured by optical biometer (p = 0.016), and anterior chamber depth by ultrasonic biometer (p < 0.016). Lens thickness remained unaffected (p ≥ 0.190). Body height and foot length were correlated with anterior chamber depth, vitreous length, and axial length (p ≤ 0.019, r ≥ 0.330). Most biometric parameters were correlated among them using both devices (p ≤ 0.037, r ≥ 0.296).

CONCLUSIONS

These biometers are not interchangeable and CL affects measurements. Body height and foot length correlate with ocular dimensions, and most ocular biometric values correlate positively.

Surgeon effects on cataract refractive outcomes are minimal compared with patient comorbidity and gender: an analysis of 490 987 cases

AIM

To investigate effect of patient age, gender, comorbidities and surgeon on refractive outcomes following cataract surgery.

METHODS

Study population: patients on UK national ophthalmic cataract database on cataract operations undertaken between 1 April 2010 and 31 August 2018. Variables examined included gender, age, diabetic retinopathy, glaucoma, high myopia, inherited retinal disease, optic nerve disease, uveitis, pseudoexfoliation, vitreous opacities, retinal pathology, cataract type, previous surgery and posterior capsular rupture. A multivariate normal cross-classified model was fitted to the refractive outcome using Markov Chain Monte Carlo (MCMC) methods with diffuse priors to approximate maximum likelihood estimation. A MCMC chain was generated with a burn-in of 5000 iterations and a monitoring chain of 50 000 iterations.

RESULTS

490 987 cataract operations were performed on 351 864 patients by 2567 surgeons. Myopic and astigmatic errors were associated with posterior capsule rupture (-0.38/+0.04×72), glaucoma (-0.10/+0.05×95), previous vitrectomy (-0.049/+0.03×66) and high myopia (-0.07/+0.03×57). Hyperopic and astigmatic errors were associated with diabetic retinopathy (+0.08/+0.03×104), pseudoexfoliation (+0.07/+0.01×158), male gender (+0.12/+0.05×91) and age (-0.01/+0.06×97 per increasing decade). Inherited retinal disease, optic nerve disease, previous trabeculectomy, uveitis, brunescent/white cataract had no significant impact on the error of the refractive outcome. The effect of patient gender and comorbidity was additive. Surgeons only accounted for 4% of the unexplained variance in refractive outcome.

CONCLUSION

Patient comorbidities and gender account for small but statistically significant differences in refractive outcome, which are additive. Surgeon effects are very small.

Retrospective Comparison of the Myopia Master and the Lenstar LS900 Axial Length Measurements in Children with Myopia

BACKGROUND

This study is a retrospective analysis to compare ocular biometry measurements of axial length in children with myopia using Myopia Master (OCULUS, Wetzlar, Germany) and Lenstar LS900 (HAAG-STREIT AG, Köniz, Switzerland).

PATIENTS AND METHODS

Axial length measurements obtained with both instruments within a 3-week period were collected retrospectively. Measurements were visualized with a Bland-Altman plot. For statistical evaluation, a paired t-test was applied, and the Pearson correlation coefficient (r) was established.

RESULTS

Sixty-one eyes from 31 myopic patients (59% male, 41% female) with a mean age of 11.34 ± 3.25 years (range: 6 - 18 years) were identified. Mean axial length was 24.7 mm (SD 1.29) with the Myopia Master and 24.69 mm (SD 1.30) with the Lenstar LS900 (Pearson correlation: r = 0.9991). The average difference of the axial length measurement between the two biometers was 0.00 064 mm ± 0.056 SD (p = 0.9293).

CONCLUSION

The axial length measured by Myopia Master and Lenstar LS900 did not differ significantly. Thus, previous values obtained with the Lenstar LS900 can be applied to assess myopia progression.

Comprehensive comparisons of ocular biometry: A network-based big data analysis

PURPOSE

To systematically compare and rank ocular measurements with optical and ultrasound biometers based on big data.

METHODS

PubMed, Embase, the Cochrane Library and the US trial registry ( www.

CLINICALTRIAL

gov ) were used to systematically search trials published up to October 22nd, 2020. We included comparative studies reporting the following parameters measured by at least two devices: axial length (AL), flattest meridian keratometry (Kf), steepest meridian keratometry (Ks), mean keratometry (Km), astigmatism (AST), astigmatism vectors J₀ and J₄₅, anterior chamber depth (ACD), aqueous depth (AQD), central corneal thickness (CCT), corneal diameter (CD) and lens thickness (LT). A network-based big data analysis was conducted using STATA version 13.1.

RESULTS

Across 129 studies involving 17,181 eyes, 12 optical biometers and two ultrasound biometers (with both contact and immersion techniques) were identified. A network meta-analysis for AL and ACD measurements found that statistically significant differences existed when contact ultrasound biometry was compared with the optical biometers. There were no statistically significant differences among the four swept-source optical coherence tomography (SS-OCT) based devices (IOLMaster 700, OA-2000, Argos and ANTERION). As for Ks, Km and CD, statistically significant differences were found when the Pentacam AXL was compared with the IOLMaster and IOLMaster 500. There were statistically significant differences for CCT when the OA-2000 was compared to Pentacam AXL, IOLMaster 700, Lenstar, AL-Scan and Galilei G6.

CONCLUSION

For AL and ACD, contact ultrasound biometry obtains the lower values compared with optical biometers. The Pentacam AXL achieves the lowest values for keratometry and CD. The smallest value for CCT measurement is found with the OA-2000.

Repeatability and comparability of a new swept-source optical coherence tomographer in optical biometry

PURPOSE

To evaluate the reproducibility in the measurement of ocular biometric parameters using a new swept-source optical coherence tomographer and its comparability with an optical low coherence reflectometry biometer.

DESIGN

An observational, descriptive, cross-sectional study.

METHODS

45 right eyes of 45 patients diagnosed with cataract were included. Three successive biometric measurements with Anterion and one with Lenstar LS900 were performed on each patient. The following variables were collected: axial length (AXL), anterior chamber depth (ACD), flat K (K1), steep K (K2), central corneal thickness (CCT), lens thickness (LT) and white-to-white distance (WTW). The intrasubject standard deviation (S_w) and the coefficient of Pearson "R" were calculated in order to assess the repeatability. The intraclass correlation coefficient (ICC) and the concordance correlation coefficient (CCC) were obtained to evaluate the comparability between devices. A Bland-Altman plot was performed for each variable.

RESULTS

The coefficient of Pearson was excellent and statistically significant in the evaluation of the repeatability in all the variables. The highest values were 0.987 (AXL), 0.983 (CCT) and 0.942 (ACD). There were no statically significant differences between repeated measurements with Anterion in all the parameters. The ICC and CCC were excellent in the evaluation of AXL, CCT and ACD, and were also good in regard to K1, K2, LT and WTW.

CONCLUSIONS

Performing biometry with the SS-OCT Anterion is a reliable and reproducible procedure, and it is comparable with the Lenstar LS900.

Comparison of 2 swept-source optical coherence tomography-based biometry devices

PURPOSE

To compare 2 swept-source optical coherence tomography (SS-OCT) biometers, IOLMaster 700 (biometer A), and ANTERION (biometer B).

SETTING

Department of Ophthalmology, Vienna Institute for Research in Ocular Surgery, Karl Landsteiner Institute, Hanusch Hospital, Vienna, Austria.

DESIGN

Retrospective study.

METHOD

Biometric measurements of cataract patients performed between June and July 2019 were reviewed. Patients scheduled for cataract surgery were measured with both SS-OCT devices on the same day. The following biometry parameters were compared: keratometry, central corneal thickness, anterior chamber depth (ACD), lens thickness (LT), and axial length (AL).

RESULT

In total, 389 eyes of 209 subjects were measured with both devices. The mean absolute difference between the keratometry data of the 2 devices was 0.04 ± 0.05 mm (7.80 ± 0.26 mm for biometer A and 7.82 ± 0.26 mm for biometer B; P < .0001) for the steep keratometry readings and 0.04 ± 0.04 mm (7.63 ± 0.26 mm and 7.65 ± 0.25 mm; P < .0001) for the flat keratometry readings. For ACD and LT, the mean absolute difference was 0.07 ± 0.04 mm and 0.07 ± 0.04 mm. The mean absolute difference for AL was 0.02 ± 0.03 mm (23.55 ± 1.18 mm for biometer A and 23.54 ± 1.18 mm for biometer B; P < .0001).

CONCLUSIONS

Good agreement was found between the 2 devices, with a minor offset for ACD and LT measurements. Although differences were found to be small, the devices should not be used interchangeably.

Long-term longitudinal changes in axial length in the Caucasian myopic and hyperopic population with a phakic intraocular lens

Purpose

To determine the long‐term longitudinal axial length changes in myopic and hyperopic adults with an iris‐fixated phakic intraocular lens (pIOL).

Methods

The medical records of patients aged ≥18 years with myopia or hyperopia who were treated with pIOL implantation between 1996 and 2011 for refractive correction with a minimum follow‐up of 5 years after pIOL implantation were analyzed. The main outcome measure was change in ocular axial length over time.

Results

149 eyes of 149 myopic patients and 27 hyperopic eyes of 27 patients were included in this study. Mean patient age was 37.1 ± 10.4 years (35% male) in the myopic group and 39.4 ± 9.4 years (4% male) in the hyperopic group. The eyes of the myopic patients showed a significant mean increase in axial length of 0.45 ± 0.61 mm after a mean follow‐up time of 144 ± 38 months (p < 0.001). In 26 eyes (17%), the axial length had increased by ≥1 mm. The mean annual axial length increase was 0.04 ± 0.06 mm. Axial elongation was associated with a higher degree of myopia (p < 0.001) and younger age (p = 0.02). The eyes of the hyperopic patients showed no change in axial length over time.

Conclusions

Myopic eyes corrected with an iris‐fixated pIOL show continuous increase in axial length at an adult age. Although this study is limited to subjects with a pIOL, this is the first time myopization in Caucasian adults has been reported in a large long‐term longitudinal study.

Sirius Scheimpflug-Placido versus ultrasound pachymetry for central corneal thickness: meta-analysis

Background

To compare the difference in central corneal thickness (CCT) measurements in normal eyes between a rotating Scheimpflug camera combined with a Placido-disk corneal topographer (Sirius, CSO, Italy) and ultrasound pachymetry (USP).

Methods

A systematic literature search was conducted for relevant studies published on PubMed, Medline, EMBASE, and the Cochrane Library and ClinicalTrials.gov from inception to August 1st, 2019. Primary outcome measures were CCT measurements between Sirius and USP. A random effects model was used to pool CCT measurements.

Results

A total of twelve studies involving 862 eyes were included in this meta-analysis. The meta-analysis found CCT measurements between Sirius and USP to be statistically significantly different (P < 0.0001). The mean difference between Sirius and USP was −11.26 μm with a 95% confidence interval (CI) (−16.92 μm, −5.60 μm). The heterogeneity was I² = 60% (P = 0.004).

Conclusion

CCT measurements with the Sirius Scheimpflug-Placido topographer were statistically significantly lower than USP. However, it may be argued that the mean difference of 11.26 μm is not a clinically significant difference.

Intraocular lens power calculation formula accuracy: Comparison of 12 formulas for a trifocal hydrophilic intraocular lens

PURPOSE

To evaluate the accuracy of 12 intraocular lens (IOL) power formulas; Barrett Universal II, Emmetropia Verifying Optical (EVO), Haigis, Hill-Radial Basis Function (RBF), Hoffer Q, Holladay I, Kane, Ladas Super Formula, Olsen _Lenstar, Panacea, Pearl-DGS, Sanders-Retzlaff-Kraff/theoretical (SRK/T). In addition, an analysis of the efficacy as a function of the axial length was performed.

METHODS

About 171 from 93 patients: 68 male eyes and 103 female eyes. Twelve IOL power formula calculations were studied with one IOL platform (trifocal hydrophilic IOL, FineVision Micro F), one biometer (Lenstar LS 900), one topographer (CSO Sirius Topographer), one surgeon, and one optometrist. Optimization were determined to be zeroed mean refractive prediction error. Mean error (ME), mean absolute error (MAE), median absolute error (MedAE) and refractive accuracy within ±1.00 D was calculated. Axial length was split in short and medium eyes.

RESULTS

One hundred and seventy eyes were included. Formulas were ranked by percentage within ±0.50 diopters and MAE (D). Among all eyes, Olsen 86.55% (0.273 D) and Barrett Universal II 86.55% (0.285D). For short eyes (<22.5 mm), Olsen 90.70% (0.273 D) and Kane 90.70% (0.225 D). For medium eyes, Barrett 89.34% (0.237 D) and Pearl 86.89% (0.263 D).

CONCLUSION

Olsen and Barrett formula obtained excellent accuracy for overall eyes. Kane and Olsen formula obtained the best results in short eyes. For medium axial length Barrett formula achieved the best accuracy results.

Effect of orthokeratology on precision and agreement assessment of a new swept-source optical coherence tomography biometer

Background

To evaluate the effect of orthokeratology on precision of measurements in children using a new swept-source optical coherence tomography (SS-OCT) optical biometer (OA-2000), and agreement between its measurements and those provided by the commonly used IOLMaster based on partial coherence interferometry (PCI).

Methods

This study recruited fifty-one eyes of 51 normal children (8–16 years). An operator took measurements with the two biometers. Then, a second operator took measurements with the SS-OCT biometer. After orthokeratology was performed for one month, the same operators repeated the same procedures. Axial length (AL), mean keratometry (Km) at 2.5 mm and 3.0 mm diameters (Km_2.5 and Km_3.0), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT) and corneal diameter (CD) were analyzed.

Results

With the SS-OCT optical biometer, the test-retest repeatability of AL measurements was < 0.06 mm. For all parameters, the coefficients of variation were < 1.23% and the intraclass correlation coefficients were > 0.95. The 95% limits of agreement of difference between the two devices for CD parameter were up to 1.53 mm. After orthokeratology, the fluctuation ranges of difference for Km3.0 measurement was 1.11 times higher than before orthokeratology, while the absolute values of difference for AL, Km2.5, ACD and CD measurements were comparable.

Conclusions

Before and after orthokeratology, the SS-OCT biometer showed high repeatability and reproducibility for all measurements. Wearing orthokeratology contact lenses affected the agreement between SS-OCT and PCI biometers for Km3.0 measurements. The CD measurement showed poor agreement between the two devices.

Refractive outcomes following cataract surgery in patients who have had myopic laser vision correction

Objective

Prediction errors are increased among patients presenting for cataract surgery post laser vision correction (LVC) as biometric relationships are altered. We investigated the prediction errors of five formulae among these patients.

Methods and analysis

The intended refractive error was calculated as a sphero-cylinder and as a spherical equivalent for analysis. For determining the difference between the intended and postoperative refractive error, data were transformed into components of Long's formalism, before changing into sphero-cylinder notation. These differences in refractive errors were compared between the five formulae and to that of a control group using a Kruskal-Wallis test. An F-test was used to compare the variances of the difference distributions.

Results

22 eyes post LVC and 19 control eyes were included for analysis. Comparing both groups, there were significant differences in the postoperative refractive error (p=0.038). The differences between the intended and postoperative refractive error were greater in post LVC eyes than control eyes (p=0.012), irrespective of the calculation method for the intended refractive error (p<0.01). The mean difference between the intended and postoperative refractive error was relatively small, but its variance was significantly greater among post LVC eyes than control eyes (p<0.01). Among post LVC eyes, there were no significant differences between the mean intended target refraction and between the intended and postoperative refractive error using five biometry formulae (p=0.76).

Conclusion

Biometry calculations were less precise for patients who had LVC than patients without LVC. No particular biometry formula appears to be superior among patients post LVC.

Agreement and Repeatability of Two Biometers to Measure Anterior Segment Components: Refractive Error Effect

BACKGROUND To assess the repeatability and agreement between a new high-resolution optical coherence tomographer (OCT) and a Scheimpflug topographer. MATERIAL AND METHODS Sixty phakic and healthy participants were measured in this study, and one eye per participant was analyzed. Depending on their refractive error, each participant was allocated into a myopic, hyperopic, or emmetropic group. The Cirrus HD-OCT 5000 (Carl Zeiss Meditec, Jena, Germany), and the Sirius Scheimpflug topographer (Costruzione Strumenti Oftalmici, Florence, Italy) were used to take all measurements. RESULTS The repeatability of these instruments to measure the anterior chamber depth, angle-to-angle, thinnest pachymetry, and both nasal and temporal angles was smaller than 0.15 mm, 0.40 mm, 10 µm, and 10 degrees, respectively. However, the repeatability of the Scheimpflug instrument to measure the apex pachymetry was about 15 µm, and for the OCT, it was about 4 µm for all groups. On average, the Sirius Scheimpflug instrument measured shallower anterior chamber depth (about 0.10 mm), shorter angle-to-angle (about 0.5 mm), thinner corneas (approximately 10 µm), and narrower angles (around 5 degrees) for all refractive groups. CONCLUSIONS The repeatability of the Cirrus OCT and Sirius Scheimpflug instrument was good and independent of the refractive error. Nevertheless, to judge whether these instruments could be used interchangeable, clinical criteria are needed.

Comparison of agreement and efficiency of a swept source-optical coherence tomography device and an optical low-coherence reflectometry device for biometry measurements during cataract evaluation

Purpose

To compare the agreement and efficiency of a swept source-optical coherence tomography biometer, IOLMaster 700 (IOLM700), and a low-coherence optical reflectometry biometer, LENSTAR LS 900 (LS900), when acquiring biometry measurements during cataract evaluation.

Methods

A retrospective chart review of biometry measurements that were performed in 64 eyes of 32 patients on the same day using the LS900 and the IOLM700. The total image acquisition time per subject was compared between the two machines using a Wilcoxon rank-sum test. Bland-Altman plots showing the mean difference and 95% limits of agreement were graphed. Intraclass correlation coefficients (ICCs) were calculated for the mean axial length (AL), anterior chamber depth (ACD), lens thickness (LT), and two keratometry mean values (K1 and K2) that were output from each device.

Results

The average time to complete biometry measurements in both eyes was significantly shorter for the IOLM700 compared with the LS900 (44.5±12.4 vs 168.8±67.2 seconds, P<0.001). The Bland-Altman analysis and ICCs showed high degrees of agreement for the mean biometry values (ICC: AL 0.9999, ACD 0.9993, LT 0.9571, K1 0.9922, K2 0.9926) generated by the two devices.

Conclusion

There was a high level of agreement between the mean biometry output measures for IOLM700 and LS900. However, it took ~73% less time on average to acquire the images when using the IOLM700 compared with the LS900. In a busy clinic setting, use of the IOLM700 for biometry measures may save time and prove more efficient.

Evaluating Refractive Outcomes after Cataract Surgery

PURPOSE

To compare methods for evaluating refractive outcomes after cataract surgery to detect outliers.

DESIGN

Case series database study of the evaluation of diagnostic technology.

PARTICIPANTS

Consecutive patients who had uneventful cataract operations over a 5-year period.

METHODS

The intended and postoperative refractive outcome and differences between these were analyzed as a spherical equivalent, cylinder, and spherocylinder. The average keratometry and differences between steep and flat keratometric meridians were used to calculate the intended refractive error.

MAIN OUTCOME MEASURES

Outliers were defined as patients for whom the difference between the intended and postoperative refractive errors was more than 3 standard deviations (SDs) away from the mean.

RESULTS

A total of 9000 patients were included. Twelve patients had missing data and were excluded. The mean intended refractive outcome was -0.12+0.12×2 (95% lower confidence limit [LCL], -1.94+1.06×44; 95% upper confidence limit [UCL], +0.77+1.05×140). The actual postoperative refractive error was -0.30+0.47×6 (95% LCL, -2.36+1.31×36; 95% UCL, +1.00+1.18×148) with a difference from the intended of -0.18+0.35×7 (95% LCL, -1.91+1.22×38; 95% UCL, +0.75+1.09×145). Treating the components of the refractive error independently, outliers were observed in 82 eyes (0.91%) based on the sphere, 46 eyes (0.51%) based on the spherical equivalent, 115 eyes (1.28%) based on treating the cylinder as a scalar, and 76 eyes (0.85%) based on treating the cylinder as a vector. When the differences between the intended and postoperative refractive errors were calculated as a compound spherocylinder, outliers were observed for 233 eyes (2.59%).

CONCLUSIONS

Treating the intended refractive outcome as a spherocylinder improves the precision for detecting clinically significant refractive outliers.

Comparison of anterior segment parameters and axial length measurements performed on a Scheimpflug device with biometry function and a reference optical biometer

PURPOSE

To compare measurements of axial length (AL), corneal curvature (K), anterior chamber depth (ACD) and white-to-white (WTW) distance on a new device combining Scheimpflug camera and partial coherence interferometry (Pentacam AXL) with a reference optical biometer (IOL Master 500). To evaluate differences between IOL power calculations based on the two biometers.

METHODS

Ninety-seven eyes of 97 consecutive cataract or refractive lens exchange patients were examined preoperatively on IOL Master 500 and Pentacam AXL units. Comparisons between two devices were performed for AL, K, ACD and WTW. Intraocular lens (IOL) power targeting emmetropia was calculated with SRK/T and Haigis formulas on both devices and compared.

RESULTS

There were statistically significant differences between two devices for all measured parameters (P < 0.05), except ACD (P = 0.36). Corneal curvature measured with Pentacam AXL was significantly flatter then with IOL Master. The mean difference in AL was clinically insignificant (0.01 mm; 95% LoA 0.16 mm). Pentacam AXL yielded higher IOL power in 75% of eyes for Haigis formula and in 62% of eyes for SRK/T formula, with a mean difference within ± 0.5 D for 72 and 86% of eyes, respectively.

CONCLUSIONS

There were statistically significant differences between AL, K and WTW measurements obtained with the compared biometers. Flatter corneal curvature measurements on Pentacam AXL necessitate formulas optimisation for Pentacam AXL.