Effect of axial length and keratometry measurement error on intraocular lens implant power prediction formulas in pediatric patients

Repeatability and agreement of total corneal astigmatism measured in keratoconic eyes using four current devices

BACKGROUND

To evaluate repeatability and agreement in measurements of total corneal astigmatism (TCA) in keratoconic eyes, using four optical coherence tomography (OCT)-based devices: Anterion, Casia SS-1000, IOLMaster 700, and MS-39.

METHODS

Three consecutive measurements were taken with each device in 136 eyes. TCA values were converted into components J0 and J45. The Anterion and the IOLMaster 700 also provided axial length (AL) measurements. The repeatability was calculated using pooled within-subject standard deviation (Sw). The agreement among the four devices was assessed by pairwise comparisons and Bland-Altman plots.

RESULTS

For all devices, the repeatability of TCA measurements showed Sw ≤0.23 D for TCA magnitude, ≤0.14 D for J0, and ≤0.12 D for J45. There were statistically significant differences in TCA magnitude for each pair, except for IOLMaster 700 with MS-39, and Anterion with MS-39. The repeatability (Sw) of axis measurements had a statistically significant negative correlation with the TCA magnitude (p < 0.001 for all devices). Both Anterion and IOLMaster 700 had high repeatability in AL measurements (Sw: 0.007 mm for Anterion and 0.009 mm for IOLMaster 700). The difference in AL between the two was 0.015 ± 0.033 mm (p < 0.001).

CONCLUSIONS

All four devices showed good repeatability in TCA measurements in keratoconic eyes, the agreement for TCA measurements between the tested devices was generally low. Anterion and IOLMaster 700 showed good repeatability and agreement in AL measurements.

Comparison of axial length and anterior segment parameters of patients with myopia measured using 2 fourier-domain optical coherent biometry devices

BACKGROUND

This study assessed the agreement of ocular parameters of patients with myopia measured using Colombo intraocular lens (IOL) 2 and IOLMaster 700.

METHODS

Eighty patients (male, 22; average age, 29.14 ± 7.36 years) with myopia (159 eyes) were included in this study in May 2023. The participants' axial length (AXL), central corneal thickness (CCT), lens thickness (LT), white-to-white distance (WTW), front flat (K1), steep (K2), mean (Km) corneal keratometry, astigmatism (Astig), J0 vector, and J45 vector were measured using the IOLMaster 700 and Colombo IOL 2. The measurements from both devices were compared using the generalized estimating equation, correlation analysis, and Bland-Altman plots.

RESULTS

With the Colombo IOL 2, lower values for K2 and J0 (odds ratio [OR] = 0.587, p = 0.033; OR = 0.779, p < 0.0001, respectively), and larger values for WTW, Astig, and J45 (OR = 1.277, OR = 1.482, OR = 1.1, all p < 0.0001) were obtained. All ocular measurements by both instruments showed positive correlations, with AXL demonstrating the strongest correlation (r = 0.9996, p < 0.0001). The intraclass correlation coefficients for AXL and CCT measured by both instruments was 0.999 and 0.988 (both p < 0.0001), and Bland-Altman plot showed 95% limits of agreement (LoA) of -0.078 to 0.11 mm and - 9.989 to 13.486 μm, respectively. The maximum absolute 95% LoA for LT, WTW, K1, K2, and J0 were relatively high, achieving 0.829 mm, 0.717 mm, 0.983 D, 0.948 D, and 0.632 D, respectively.

CONCLUSIONS

In young patients with myopia, CCT and AXL measurements obtained with the Colombo IOL 2 and IOLMaster 700 were comparable. However, WTW, LT, corneal refractive power, and astigmatism values could not be used interchangeably in clinical practice.

Comparison of a New Scheimpflug Camera and Swept-Source Optical Coherence Tomographer for Measurements of Anterior Segment Parameters

INTRODUCTION

This study evaluated the differences and agreement between a new Scheimpflug camera (Scansys) and a swept-source anterior segment optical coherence tomographer (CASIA 2) for measurements of the anterior segment of the eye in normal subjects.

METHODS

This prospective study included 84 eyes from 84 normal adult subjects who underwent three consecutive measurements with the Scansys and the CASIA 2 in random order. The mean keratometry (Km), astigmatism magnitude (AST), J0, and J45 vectors for both anterior and posterior corneal surfaces, central corneal thickness (CCT), thinnest corneal thickness (TCT), and anterior chamber depth (ACD) were obtained by both devices. The difference between these two devices was assessed using paired t test and violin plots. Bland-Altman plots and 95% limits of agreement (LoAs) were used to evaluate agreement.

RESULTS

No statistically significant differences between the two devices were found for the anterior AST, anterior J45, and posterior J45 (P > 0.05). The remaining parameters were statistically significant (P ≤ 0.05), but the differences not clinically significant. The violin plots showed that the distribution and probability density of the measured parameters were similar for both devices. Bland-Altman plots revealed high agreement for the measured parameters between the Scansys and CASIA 2, with narrow 95% LoAs.

CONCLUSIONS

In terms of assessing parameters for the anterior segment, our study indicated that Scansys and CASIA 2 generally showed significant agreement. The two devices used in this study's assessment of all the parameters can be used interchangeably in refractive analysis.

A Bayesian network meta-analysis on comparisons of intraocular lens power calculation methods for paediatric cataract eyes

The study aimed to compare and rank the accuracy of formulas for calculating intraocular lens (IOL) power in paediatric eyes in a systematic way. A literature search was conducted in Pubmed, Web of Science, Cochrane Library, and EMBASE by December 2021. Combined with traditional and network meta-analysis, we analysed the percentages of paediatric eyes with prediction error (PE) within ±0.50 dioptres (D) and ±1.00 D as the outcome measurements among different formulas. Subgroup analyses stratified by age were also undertaken. Thirteen studies with 1781 eyes comparing 8 calculation formulas were included. For the traditional meta-analysis results, Sanders-Retzlaff-Kraff theoretical (SRK/T) (risk ratios (RR), 1.15; 95% confidence intervals (CI), 1.03-1.30) performed significantly better than the SRKII formula for the percentage of eyes with PE within ±0.50 D. In addition, SRK/T (RR, 1.10; 95% CI, 1.02-1.18) and Holladay 1(RR, 1.15; 95% CI, 1.01-1.30) both performed significantly better than the SRKII formula for the percentage of eyes with PE within ±1.00 D. Considering the ranking based on the surface under the cumulative ranking curve (SUCRA) by Bayesian method, the top four formulas were Barrett Universal II (UII), Haigis, Holladay 1, and SRK/T on the percentage of PE within ±0.50 D, whereas the top four formulas were Barrett UII, Holladay 1, SRK/T, and Hoffer Q formulas on the percentage of PE within ±1.00D. Concerning both outcome measurements of rank probabilities, the top three Barrett UII, SRK/T, and Holladay 1 formulas were considered to provide more accuracy for IOL power calculation in paediatric cataract eyes, and Barrett UII tends to perform better in older children.

Agreement of Total Keratometry and Posterior Keratometry Among IOLMaster 700, CASIA2, and Pentacam

Purpose

The purpose of this study was to compare total keratometry (TK) and posterior keratometry (PK) obtained by two swept-source optical biometers (IOLMaster 700 and CASIA2) and one Scheimpflug-based topography (Pentacam AXL).

Methods

The TK and PK in cataract surgery candidates obtained by IOLMaster 700, CASIA2, and Pentacam AXL were compared. Intraclass correlation coefficients (ICCs), limit of agreement, and Bland-Altman plots were used to assess the agreement.

Results

One hundred two patients with a mean age of 68.21 ± 8.70 years were included. There were significant differences among IOLMaster 700, CASIA2, and Pentacam AXL in the mean TK (TKm) (44.23 ± 1.59 diopters [D] vs. 43.25 ± 1.53 D vs. 43.94 ± 1.68 D; all P < 0.001), mean PK (PKm; -5.90 ± 0.24 D vs. -6.25 ± 0.25 D vs. -6.37 ± 0.26 D; all P < 0.001) and TK-J0 (-0.34 ± 0.65 D vs. -0.23 ± 0.53 D vs. -0.12 ± 0.62 D; all P < 0.001). We also observed significant differences in PK-J45 between IOLMaster 700 and Pentacam AXL as well as between CASIA2 and Pentacam AXL (both P < 0.001). There was a good agreement in TKm, TK-J0, TK-J45, and PK-J0 (ICC = 0.887, 0.880, 0.751, and 0.807, respectively), a moderate agreement in PK-J45 (ICC = 0.626), and a poor agreement in PKm (ICC = 0.498) among these 3 biometers.

Conclusions

TK, PK, and the corresponding astigmatism obtained by IOLMaster 700, CASIA2, and Pentacam AXL showed significant differences, and could not be used interchangeably.

Translational Relevance

Our study may help to guide preoperative keratometry measurement for intraocular lens (IOL) power calculation and astigmatism evaluation for patients with cataract.

Effect of pupil dilation on biometry measurements and intraocular lens power in eyes with high myopia

Purpose

The present study sought to evaluate the effects of pupil dilation on ocular parameter measurements and intraocular lens (IOL) power calculation using IOLMaster in highly myopic cataract patients.

Materials and methods

A total of 233 eyes were included in this prospective study and assigned to four groups based on range of axial length (AL) as follows: group A:26–28 mm, group B:28–30 mm, group C:30–32 mm, and group D:32–36 mm. Flattest and steepest keratometry (K1 and K2), AL, anterior chamber depth (ACD), lens thickness (LT), and white-to-white (WtW) were determined using IOLMaster before and after administration of topical tropicamide. The corresponding IOL powers were calculated using Sanders–Retzlaff–Kraff/theoretical (SRK/T), Haigis, and Barrett Universal II formulas.

Results

Variations in AL, K1 and K2 following dilation were not significant (P > 0.05 in all groups). The results showed that ACD increased significantly after dilation (P = 0.000 in all groups), whereas LT decreased significantly after dilation (P = 0.000, 0.000, 0.001, and 0.003). Post-dilation WtW increased significantly in Group A, B, and C (P = 0.001, 0.001, and 0.025) but not in Group D. When IOL power was calculated as a discrete variable, significant differences were observed between pre- and post-dilation IOL power.

Conclusion

Pupil dilation in cataract eyes with high myopia does not cause significant changes in AL and K. However, it significantly increases ACD as well as WtW values and significantly decreases the LT value. Surgeons should evaluate the effect of pupil dilation on IOL power prediction as the present findings show extreme cases. Notably, Barrett Universal II formula had the best concordance between different pupil conditions in long eyes.

Accuracy of Intraocular Lens Power Calculation Formulas in Patients With Multifocal Intraocular Lens Implantation With Optic Capture in Berger Space for Pediatric Cataract

PURPOSE

To assess the accuracy of intraocular lens (IOL) calculation formulas in pediatric patients with multifocal IOL implantation with optic capture in Berger space.

METHODS

This prospective observational study enrolled 68 children (101 eyes), aged 3 to 14 years, who received multifocal IOL (Tecnis ZMB00; Abbott Medical Optics) implantation with optic capture in Berger space from June 2019 to June 2020 in Qingdao Eye Hospital. Ocular biometry was performed using the IOLMaster 700 (Carl Zeiss Meditec). The IOL power and intended postoperative refraction were calculated using the Hoffer Q, Barrett Universal II, Holladay, Holladay2, SRK/T, Haigis, and SRKII formulas. The refractive state of patients, prediction error, and absolute prediction error were evaluated.

RESULTS

The mean absolute error of the formulas was significantly different (0.49 diopters [D], Hoffer Q; 0.52 D, Barrett Universal II; 0.47 D, Holladay; 0.54 D, Holladay2; 0.52 D, SRK/T; 0.67 D, Haigis; 0.99 D, SRKII; P < .001). However, the Hoffer Q, Barrett Universal II, Holladay, Holladay2, and SRK/T formulas had a similar accuracy in predicting refractive error within ±0.50 D (62.4%, 59.4%, 62.4%, 62.4%, and 58.4%). There was a trend toward a greater prediction error in eyes with a shorter axial length (≤ 22 mm) or a steeper cornea (> 43.50 D), for which the Hoffer Q and Holladay2 formulas were more accurate. When the axial length was greater than 22 mm or the corneal curvature was 43.50 D or less, the Holladay, Hoffer Q, and Barrett Universal II formulas were more accurate.

CONCLUSIONS

For patients with pediatric cataract treated with multifocal IOL implantation with optic capture in Berger space, the Hoffer Q, Barrett Universal II, Holladay, Holladay2, and SRK/T formulas performed better than the other formulas. [J Pediatr Ophthalmol Strabismus. 20XX;X(X):XX-XX.].

Challenges in pediatric cataract surgery: comparison of intraocular lens power calculation formulas using optical biometry

PURPOSE

Comparison of the accuracy of intraocular lens (IOL) power calculation formulas (SRK II, SRK/T, Holladay 1, Hoffer Q and Barrett II Universal, Haigis) in pediatric cataract surgery using optical biometry.

METHOD

This prospective study included seventy eyes of 70 patients between ages of 3-15 who had undergone cataract surgery with IOL implantation. Anterior segment parameters and axial length (AL) were measured with an optical biometer. Barrett II Universal formula results were used to determine the diopter of implanted IOL. Postoperative refraction was taken at first month, and differences from the estimated refractive value [mean absolute predictive error (APE)] were compared between formulas. Formulas were also compared according to AL.

RESULTS

The lowest APE was achieved with Barrett II formula (0.64 ± 0.73D) and the highest with Haigis formula (1.06 ± 0.84D) in the whole study population (p < 0.01). APE values were lowest with Holladay 1 (0.79 ± 0.71D) and highest with Haigis (1.44 ± 0.92D) in patients with an AL ≤ 22 mm; lowest APE was achieved with Barrett II (0.47 ± 0.54D) and highest with Haigis (0.84 ± 0.72D) in patients with an AL > 22 mm.

CONCLUSION

Barrett II formula had the best results in eyes with average AL, and SRK/T and Holladay 1 formulas were better in eyes with shorter AL. Haigis formula statistically had the highest predictive error in all formulas.

Intraocular lens power calculation formula in congenital cataracts: Are we using the correct formula for pediatric eyes?

The major challenge these days in pediatric cataract surgery is not the technique of surgery or intraocular lens (IOL) used but the postoperative refractive error. Amblyopia occurring due to postoperative refractive error which the child has; destroys the benefit obtained by a near-perfect and timely surgery. Even if we settle the debate as to what should be the ideal postoperative target refraction, there is a postoperative surprise that is not explained by our conventional insights of an accurate power calculation in children. The role of IOL power calculation formulae in affecting the postoperative refractive error should not be underestimated. Therefore, which age-appropriate formula is to be used for children is unclear. This review is an update on major IOL power calculation formulas used in pediatric eyes. We have tried to define why we should not be using these formulas made for adult eyes and review the literature in this regard.

Refractive prediction of four different intraocular lens calculation formulas compared between new swept source optical coherence tomography and partial coherence interferometry

Purpose

To compare the biometry and prediction of postoperative refractive outcomes of four different formulae (Haigis, SRK/T, Holladay1, Barrett Universal II) obtained by swept-source optical coherence tomography (SS-OCT) biometers and partial coherence interferometry (PCI; IOLMaster ver 5.4).

Methods

We compared the biometric values of SS-OCT (ANTERION, Heidelberg Engineering Inc., Heidelberg, Germany) and PCI (IOLMaster, Carl Zeiss Meditec, Jena, Germany). Predictive errors calculated using four different formulae (Haigis, SRKT, Holladay1, Barrett Universal II) were compared at 1 month after cataract surgery.

Results

The mean preoperative axial length (AL) showed no statistically significant difference between SS-OCT and PCI (SS-OCT: 23.78 ± 0.12 mm and PCI: 23.77 ± 0.12 mm). The mean anterior chamber depth (ACD) was 3.30 ± 0.04 mm for SS-OCT and 3.23 ± 0.04 mm for PCI, which was significantly different between the two techniques. The mean corneal curvature also differed significantly between the two techniques. The difference in mean arithmetic prediction error was significant in the Haigis, SRKT, and Holladay1 formulae. The difference in mean absolute prediction error was significant in all four formulae.

Conclusions

SS-OCT and PCI demonstrated good agreement on biometric measurements; however, there were significant differences in some biometric values. These differences in some ocular biometrics can cause a difference in refractive error after cataract surgery. New type SS-OCT was not superior to the IOL power prediction calculated by PCI.

Comparison study of the axial length measured using the new swept-source optical coherence tomography ANTERION and the partial coherence interferometry IOL Master

Purpose

To compare a biometer using swept-source optical coherence tomography (SS-OCT) with a partial coherence interferometry (PCI)-based biometer in measurements of two ocular biometry parameters, i.e., the axial length and anterior cornea curvature.

Methods

We compared the two biometers SS-OCT (ANTERION, Heidelberg Engineering Inc., Heidelberg, Germany) and PCI (IOL Master, Carl Zeiss Meditec, Jena, Germany) in terms of the axial length (AL) and corneal curvature (K) measurements of 175 eyes. Paired t-tests were used to compare the two biometers. Agreement between the biometers was evaluated using the Bland–Altman method.

Results

The mean age was 36.0 ± 25.6 years (range: 5 to 85 years). The mean axial length was 24.42 ± 0.13 mm for SS-OCT and 24.45 ± 0.14 mm for PCI. The mean corneal curvature was significantly different between the two biometry in flat K (K1) but not in steep K (K2). The limit of agreement was -0.15 to 0.21 in the axial length, -1.18 to 0.83 in K1, and -1.06 to 0.95 in K2. All above ocular biometric measurements between SS-OCT and PCI correlated significantly (Pearson's correlation, p<0.001).

Conclusions

The axial length measured using SS-OCT is useful in clinical practice. It shows a good correlation and agreement with that measured using PCI. However, the axial length and corneal curvature measured using SS-OCT cannot be used interchangeably with that measured using PCI in clinical practice.

Comparison of the Accuracy of IOL Power Calculation Formulas for Pediatric Eyes in Children of Different Ages

Purpose

This study aims to compare the accuracy of five intraocular lens (IOL) power calculation formulas (SRK/T, Hoffer Q, Holladay 1, Haigis, and Holladay 2) for pediatric eyes in children of different ages.

Methods

In this prospective study, patients who received cataract surgery and IOL implantation in the capsular bag were enrolled. We compared the calculation accuracy of 5 formulas at 1 month postoperatively and performed subgroup analysis with the patients divided into three groups according to their ages at the time of surgery as follows: group 1 (age ≤ 2 years, 35 eyes), group 2 (2 years < age < 5 years, 38 eyes), and group 3 (age > 5 years, 29 eyes).

Results

75 patients (102 eyes) were enrolled in this study. The Haigis formula got the smallest PE among all formulas in all three groups. With regard to APE, there were no statistical differences among the formulas except group 2, with the SRK/T formula a little smaller, the Holladay 2 formula a little larger in group 1, and the Haigis formula a little smaller in group 3. In group 2, the Haigis formula had the lowest APE (0.87 ± 0.61 D), while the Holladay 2 formula had the largest (1.71 ± 1.20 D, p < 0.001), followed by the Holladay 1 formula (1.51 ± 1.07 D, p=0.002). On comparing the percentage of APE within 0.5 D and 1.0 D obtained with 5 formulas in each group, there were no statistical differences. The SRK/T formula and the Holladay 1 formula showed the highest percentage (40.00% and 60.00%) in group 1. While the Haigis formula got the highest percentage in less than 0.5 D (34.21%) and less than 1 D (60.53%) in group 2. In group 3, the Holladay 2 formula and the Haigis formula got the highest percentage less than 0.5 D (58.62%) and less than 1 D (79.31%). The multiple linear regression indicated that the age at the time of surgery was a significant factor affecting the accuracy of APE; after removing the age, AL was the only factor that affected the accuracy of APE.

Conclusion

The SRK/T and the Holladay 1 formulas were relatively accurate in patients younger than 2 years old, while the Haigis formula performed better in patients older than 2.

Effect of photorefractive keratectomy on agreement of anterior segment variables obtained by a swept-source biometer vs a Scheimpflug-based tomographer

PURPOSE

To evaluate agreement of anterior segment variables between Pentacam-AXL and IOLMaster 700 before vs after photorefractive keratectomy (PRK).

SETTING

Salouti Eye Clinic, Shiraz, Iran.

DESIGN

Prospective cohort with interdevice agreement analysis.

METHODS

This study included healthy PRK candidates who were assessed with both devices preoperatively and 6 months after PRK. Only data from the right eye of each patient was analyzed. Pentacam-AXL average keratometry (AvgK) and zonal keratometry in the central 2.5 mm zone (zonal-K2.5) were each compared with mean keratometry (Km) from the IOLMaster 700. Other main outcome measures included vector analysis of corneal astigmatism (J0 and J45), central corneal thickness (CCT), anterior chamber depth (ACD), and white-to-white (WTW) distance. Axial length (AL) measurements by the same devices on a new cohort of 40 patients who had undergone PRK were also assessed. A paired t test was used to assess the interdevice measurement differences, and Bland-Altman analysis was used to calculate the 95% limits of agreement (LoA).

RESULTS

This study included 97 patients. Preoperative vs post-PRK 95% LoAs between Pentacam-AXL and IOLMaster 700 were as follows: AvgK/Km (-0.42, 0.08 diopter [D]) vs (-0.49, 0.18 D); zonal-K2.5/Km (-0.40, 0.32 D) vs (-0.57, 0.74 D); J0 (-0.33, 0.18 D) vs (-0.28, 0.35 D); J45 (-0.28, 0.23 D) vs (-0.24, 0.27 D); pupil pachymetry/CCT (-18, 12 μm) vs (-2.6, 19.6 μm); apical pachymetry/CCT (-17.4, 12.8 μm) vs (-1.7, 20.9 μm); ACD (-0.03, 0.13 mm) vs (-0.03, 0.13 mm); WTW (-0.68, 0.23 mm) vs (-0.63, 0.14 mm); and AL (-0.07, 0.01 mm) vs (-0.07, 0.03 mm), respectively.

CONCLUSIONS

PRK showed a negative impact on interdevice agreement for CCT and corneal power measurements, whereas it did not have a significant effect on the agreement of devices for ACD, WTW, AL, and the J45 astigmatism vectoral component. For IOL power measurement in post-PRK eyes, the 2 devices could be regarded as interchangeable for measuring AL and ACD but not for keratometry readings.

Intraocular lens power calculation in a posterior chamber phakic intraocular lens implanted eye

PURPOSE

To evaluate the effect of Eyecryl posterior chamber phakic intraocular lens (pIOL) on axial length measurement and intraocular lens power calculation.

METHODS

Axial length (AL), keratometry (K), and IOL power calculations were compared at monthly preoperative and postoperative visits (preoperative vs 1-month). Preoperative IOL power (calculated using preoperative K and AL) was compared with a re-calculation where the pIOL was assumed to be in the posterior chamber (calculated using preoperative K value and postoperative AL).

RESULTS

Thirty-nine eyes of 39 patients were included. The mean preoperative AL and postoperative AL were 27.02 ± 1.50 and 27.17 ± 1.52 mm (p < 0.001), respectively. The mean preoperative and recalculated IOL powers to achieve emmetropia were 9.40 ± 3.35 and 8.98 ± 3.37 D (p < 0.001) with SRK-T formula, 8.82 ± 3.54 and 8.47 ± 3.60 (p = 0.02) with Holladay I formula, and 9.78 ± 3.43 and 9.44 ± 3.50 (p = 0.013) with Hoffer Q formula.

CONCLUSION

The presence of Eyecryl pIOL in the posterior chamber results in a small increase in the AL measurement, and this might result in a corresponding hypermetropic shift in the desired refraction.

[Factors influencing target refraction in children with pseudophakia after extraction of congenital cataract]

The article describes the factors affecting the target refraction of pseudophakic eyes of children after extraction of congenital cataracts. The factors include features of the echobiometric parameters of the eye, refraction, comorbidity of congenital cataracts and ocular pathologies, margins of error in calculating strength of the intraocular lens, localization and structure of the artificial lens, as well as correction of obscure or refractive amblyopia in pseudophakic eyes. Development of the algorithm for correction of residual refraction of pseudophakic eyes in children both before and after IOL implantation with consideration of each of those factors currently remains a relevant problem.

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

PURPOSE

To evaluate the repeatability of a new biometer using Scheimpflug technology combined with partial coherence interferometry (PCI) (Pentacam AXL) and its agreement with a device based on optical low-coherence reflectometry (OLCR), the Allegro Biograph.

SETTING

Oftalvist Centro Integral Ocular Jerez, Jerez de la Frontera, Spain.

DESIGN

Evaluation of a diagnostic test.

METHODS

The mean keratometry (K), central corneal thickness (CCT), anterior chamber depth (ACD), and axial length (AL) were measured with the 2 devices 3 times by the same examiner in 2 groups (patients with cataract and patients without cataract). The repeatability was determined using the within-subject standard deviation, test-retest repeatability, coefficient of variation, and intraclass correlation coefficient. The correlation was evaluated with the Pearson coefficient and interchangeability with the Bland-Altman plot.

RESULTS

Eighty eyes (40 eyes in each group) of 80 patients were analyzed. Significant differences were found between the Scheimpflug-PCI device and the OLCR device for mean K in the normal group (P < .001) and for CCT in the normal group (P < .05) and the cataract group (P < .001). There were no differences between devices in ACD and AL in either group. The repeatability between devices was similar. Although a significant correlation between devices was found for all measurements (all P < .001), wide limits of agreement were found in both groups for all biometric parameters.

CONCLUSIONS

The Scheimpflug-PCI and OLCR devices showed excellent intravisit repeatability and high correlation for mean K, CCT, ACD, and AL in healthy and cataractous eyes. No differences were found in AL; however, the 2 devices might not be interchangeable.

Predictability of formulae for intraocular lens power calculation according to the age of implantation in paediatric cataract

Aims

To analyse the predictability of diverse intraocular lens (IOL) power calculation formulae in paediatric patients with congenital cataract.

Methods

The medical records of patients who underwent cataract surgery and posterior chamber IOL implantation (in-the-bag) for congenital cataract before 17 years of age were reviewed retrospectively. Target refractions calculated by Sanders-Retzlaff-Kraff (SRK)/II, SRK/T and Hoffer-Q formulae were compared with the actual refraction. Patients were subgroup according to the age at IOL implantation (age group 0–24 months, 25–60 months, 61–120 months, 121–203 months), and we compared mean prediction error (PE) and mean absolute error (AE) for each formula. Corrected AE was obtained by linear regression analysis.

Results

Totally 481 eyes were included in the final analysis. Both SRK/II and SRK/T yielded the lowest mean AE in the age group 0–24 months and SRK/II yielded the lowest mean AE in the age group 25–60 months. For every formula, the mean PE was positive during the first five years of age, which converged to zero according to age as IOL implantation increases. The tendency for immediate postoperative overcorrection in younger patients (<6 years) could be improved by corrected formulae based on the linear regression equation.

Conclusions

Patients with congenital cataract who underwent IOL implantation within 5 years of age showed higher AE than the older ones did. Among the three formulae evaluated, SRK/II consistently provided the best predictive result in these patients. For patients aged >10 years, all three formulae showed favourable predictive abilities.

Repeatability of Ophtha Top topography and comparison with IOL-Master and LenstarLS900 in cataract patients

AIM

To determine the repeatability of Ophtha Top topography and assess the consistency with intraocular lens (IOL)-Master and LenstarLS900 (Lenstar) in measuring corneal parameters among cataract patients.

METHODS

Totally 125 eyes were enrolled. Corneas were successively measured with Ophtha Top, IOL-Master and Lenstar at least three times. The flattest meridian power (Kf), the steepest meridian power (Ks), mean power (Km), J0 and J45 were recorded. Intra-class correlation coefficients (ICCs), the coefficient of variance (COV), within subject standard deviation (Sw), and test-retest repeatability (2.77Sw) were adopted to determine the repeatability. The 95% limit of agreement (95%LOA) and Bland-Altman plots were used to assess comparability.

RESULTS

Repeatability of Ophtha Top topography for measuring corneal parameters showed the ICCs were all above 0.93, 2.77Sw was lower than 0.31, and the COV of the Kf and Ks was lower than 0.25. The keratometric readings with Ophtha Top topography were flatter than with the IOL-Master and Lenstar devices, while the Pearson correlation coefficients were over 0.97. The J0 and J45 with Ophtha Top topography were smaller compared with Lenstar and IOL-Master, while was comparable between Lenstar and IOL-Master.

CONCLUSION

Ophtha Top topography shows excellent repeatability for measuring corneal parameters. However, differences between the Ophtha TOP topography and Lenstar, IOL-Master both in cornea curvature and the astigmatism should be noted clinically.

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

A meta-analysis to compare ocular biometry measured by optical low-coherence reflectometry (Lenstar LS900; Haag Streit) and partial coherence interferometry (the IOLMaster optical biometer; Carl Zeiss Meditec). A systematic literature search was conducted for articles published up to August 6th 2015 in the Cochrane Library, PubMed, Medline, Embase, China Knowledge Resource Integrated Database and Wanfang Data. A total of 18 studies involving 1921 eyes were included. There were no statistically significant differences in axial length (mean difference [MD] 0 mm; 95% confidence interval (CI) −0.08 to 0.08 mm; p = 0.92), anterior chamber depth (MD 0.02 mm; 95% CI −0.07 to 0.10 mm; p = 0.67), flat keratometry (MD −0.05 D; 95% CI −0.16 to 0.06 D; p = 0.39), steep keratometry (MD −0.09 D; 95% CI −0.20 to 0.03 D; p = 0.13), and mean keratometry (MD −0.15 D; 95% CI −0.30 to 0.00 D; p = 0.05). The white to white distance showed a statistically significant difference (MD −0.14 mm; 95% CI −0.25 to −0.02 mm; p = 0.02). In conclusion, there was no difference in the comparison of AL, ACD and keratometry readings between the Lenstar and IOLMaster. However the WTW distance indicated a statistically significant difference between the two devices. Apart from the WTW distance, measurements for AL, ACD and keratometry readings may be used interchangeability with both devices.

Paediatric intraocular lens implants: accuracy of lens power calculations

PurposeThis study aims to evaluate the accuracy of lens prediction formulae on a paediatric population.MethodsA retrospective case-note review was undertaken of patients under 8 years old who underwent cataract surgery with primary lens implantation in a regional referral centre for paediatric ophthalmology, excluding those whose procedure was secondary to trauma. Biometric and refractive data were analysed for 43 eyes, including prediction errors (PE). Statistical measures used included mean absolute error (MAE), median absolute error (MedAE), Student's t-test and Lin's correlation coefficient.ResultsThe mean PE using the SRK-II formula was +0.96 D (range -2.47D to +2.41 D, SD 1.33 D, MAE 1.38 D, MedAE 1.55, n=15). The mean PE was smaller using SRK/T (-0.18 D, range -3.25 D to +3.95 D, SD 1.70 D, MAE 1.30 D, MedAE 1.24, n=27). We performed an analysis of the biometry data using four different formula (Hoffer Q, Holladay 1, SRK-II and SRK/T). Hoffer Q showed a smaller MedAE than other formulae but also a myopic bias.ConclusionOur clinical data suggest SRK/T was more accurate in predicting post-operative refraction in this cohort of paediatric patients undergoing cataract surgery. Hoffer Q may have improved accuracy further.

Effect of general anesthesia and muscle relaxants on keratometry measurements using a handheld keratometer

PURPOSE

Keratometry measurements are often obtained under general anesthesia in the supine position in difficult patients and pediatric procedures. This study investigates the effect of general anesthesia and muscle relaxants on keratometry readings using a handheld keratometer.

METHODS

Fifty patients (with no history of intraocular surgery or corneal pathology) undergoing general anesthesia were prospectively enrolled. Keratometry readings were obtained using the Nidek KM-500 handheld keratometer (Nidek, Inc., Fremont, CA). in three settings: when the patient was awake in the upright and supine positions, and after general anesthesia. Readings were averaged in each eye and compared among the three settings; patients were also subgrouped by whether muscle relaxants were administered at induction. Intraclass correlation coefficients were calculated and Bland-Altman analysis was performed.

RESULTS

Keratometry readings were comparable between the upright and supine positions before anesthesia in all groups. In the muscle relaxant group, keratometry readings were flatter after anesthesia and this was statistically significant for right eyes (P = .02), but not for left eyes (P = .16). In the group with no muscle relaxant, no significant differences were noted. Intraclass correlation coefficients of the differences were high (≥ 0.97) for all eyes in both groups and Bland-Altman plots showed most of the differences to be within the limits of agreement.

CONCLUSIONS

Keratometry readings using the handheld keratometer obtained under general anesthesia were as reliable as readings obtained in the awake state, regardless of posture; administration of muscle relaxants at induction may produce flatter keratometry readings.

Agreement study of keratometric values measured by Biograph/LENSTAR, auto-kerato-refractometer and Pentacam: decision for IOL calculation

BACKGROUND

The aim was to determine the agreement in keratometric readings measured with the Biograph/LENSTAR, the Pentacam and an auto-kerato-refractometer in a 40- to 64-year-old population.

METHODS

This report is part of the first phase of the population-based Shahroud Cohort Eye Study. In virgin eyes, agreement among keratometry readings of three devices was examined in 7,260 eyes using the Bland-Altman method. The inter-device 95 per cent limits of agreement (95% LoA) and 95% confidence interval for upper and lower limits of agreement were calculated. Comparisons were made for keratometric readings of the flat and steep meridians as maximum keratometry (max-K), minimum keratometry (min-K) and their average (mean-K).

RESULTS

Based on Biograph/LENSTAR measurements, averages of max-K, min-K and mean-K were 44.70 ± 1.64, 43.87 ± 1.54 and 44.28 ± 1.58 D, respectively. The quantile-quantile plot revealed that all three variables had normal distributions in this population. Agreement between the Biograph/LENSTAR and the auto-kerato-refractometer (max-K difference: -0.03 D, 95% LoA: -0.81 to 0.75; min-K difference: -0.08 D, 95% LoA: -0.85 to 0.68) was better than the agreement between the Biograph/LENSTAR and the Pentacam (max-K difference: 0.50 D, 95% LoA: -3.24 to 4.25; min-K difference: 0.59 D, 95% LoA: -3.00 to 4.17). The agreement between the Pentacam and the auto-kerato-refractometer (max-K difference: 0.54 D, 95% LoA: -3.16 to 4.24; min-K difference: 0.66 D, 95% LoA: -0.77 to 0.53) was worse than the other two pairs.

CONCLUSION

These three devices are not interchangeable in terms of keratometry for calculation of the intraocular lens power. Agreement between the Biograph/LENSTAR and the auto-kerato-refractometer can be increased with regression models but this is not true in case of Biograph/LENSTAR and Pentacam.

Predictability of intraocular lens power calculation formulae in infantile eyes with unilateral congenital cataract: results from the Infant Aphakia Treatment Study

PURPOSE

To compare accuracy of intraocular lens (IOL) power calculation formulae in infantile eyes with primary IOL implantation.

DESIGN

Comparative case series.

METHODS

The Hoffer Q, Holladay 1, Holladay 2, Sanders-Retzlaff-Kraff (SRK) II, and Sanders-Retzlaff-Kraff theoretic (SRK/T) formulae were used to calculate predicted postoperative refraction for eyes that received primary IOL implantation in the Infant Aphakia Treatment Study. The protocol targeted postoperative hyperopia of +6.0 or +8.0 diopters (D). Eyes were excluded for invalid biometry, lack of refractive data at the specified postoperative visit, diagnosis of glaucoma or suspected glaucoma, or sulcus IOL placement. Actual refraction 1 month after surgery was converted to spherical equivalent and prediction error (predicted refraction - actual refraction) was calculated. Baseline characteristics were analyzed for effect on prediction error for each formula. The main outcome measure was absolute prediction error.

RESULTS

Forty-three eyes were studied; mean axial length was 18.1 ± 1.1 mm (in 23 eyes, it was <18.0 mm). Average age at surgery was 2.5 ± 1.5 months. Holladay 1 showed the lowest median absolute prediction error (1.2 D); a paired comparison of medians showed clinically similar results using the Holladay 1 and SRK/T formulae (median difference, 0.3 D). Comparison of the mean absolute prediction error showed the lowest values using the SRK/T formula (1.4 ± 1.1 D), followed by the Holladay 1 formula (1.7 ± 1.3 D). Calculations with an optimized constant showed the lowest values and no significant difference between the Holladay 1 and SRK/T formulae (median difference, 0.3 D). Eyes with globe AL of less than 18 mm had the largest mean and median prediction error and absolute prediction error, regardless of the formula used.

CONCLUSIONS

The Holladay 1 and SRK/T formulae gave equally good results and had the best predictive value for infant eyes.

Pediatric intraocular lens power calculations

PURPOSE OF REVIEW

To implant an appropriate intraocular lens (IOL) in a child, we must measure the eye well, calculate the IOL power accurately and predict the refractive change of the pseudophakic eye to maturity. The present review will concentrate on recent studies dealing with these issues.

RECENT FINDINGS

Immersion A-scan biometry is superior in measuring the axial length of children. Current IOL power calculation formulas are very accurate in adults, but significantly less accurate in children. Several studies point to the high prediction errors encountered particularly in shorter eyes with all available IOL formulas. Postoperative refraction target remains controversial, but low degrees of overcorrection (i.e. hyperopia) may not adversely affect eventual best-corrected visual acuity.

SUMMARY

Although pediatric IOL power calculations suffer from significant prediction error, these errors can be decreased by careful preoperative measurements. IOL power calculation formulas are most accurate in the older, more 'adult'-sized eye. The smallest eyes have the most prediction error with all available formulas. Individual circumstances and parental concerns must be factored into the choice of a postoperative refractive target.

Refractive changes after removal of anterior IOLs in temporary piggyback IOL implantation for congenital cataracts

Purpose

To assess the refractive change and prediction error after temporary intraocular lens (IOL) removal in temporary polypseudophakic eyes using IOL power calculation formulas and Gills' formula.

Methods

Four consecutive patients (7 eyes) who underwent temporary IOL explantation were enrolled. Postoperative refractions calculated using IOL power calculation formulas (SRK-II, SRK-T, Hoffer-Q, Holladay, and the modified Gills' formula for residual myopia and residual hyperopia) were compared to the manifest spherical equivalents checked at 1 month postoperatively.

Results

The mean ages of temporary piggyback IOL implantation and IOL removal were 6.71 ± 3.68 months (range, 3 to 12 months) and 51.14 ± 18.38 months (range, 29 to 74 months), respectively. The average refractive error was -13.11 ± 3.10 diopters (D) just before IOL removal, and improved to -1.99 ± 1.04 D after surgery. SRK-T showed the best prediction error of 1.17 ± 1.00 D. The modified Gills' formula for myopia yielded a relatively good result of 1.47 ± 1.27 D, with only the variable being axial length.

Conclusions

Formulas to predict refractive change after temporary IOL removal in pediatric polypseudophakia were not as accurate as those used for single IOL implantation in adult eyes. Nonetheless, this study will be helpful in predicting postoperative refraction after temporary IOL removal.

Update of intraocular lens implantation in children

Cataract is a common problem that affects the vision in children and a major cause of amblyopia in children. However, the management of childhood cataract is tenuous and requires special considerations especially with regard to intraocular lens (IOL) implantation. Age at which an IOL can be implanted is a controversial issue. Implanting an IOL in very young children carries the risk of severe postoperative inflammation and posterior capsule opacification that may need other surgeries and may affect the vision permanently. Accuracy of the calculated IOL power is affected by the short eyes and the steep keratometric values at this age. Furthermore, choosing an appropriate IOL power is not a straight forward decision as future growth of the eye affects the axial length and keratometry readings which may result in an unexpected refractive error as children age. The aim of this review is to cover these issues regarding IOL implantation in children; indications, timing of implantation, types of IOLs, site of implantation and the power calculations.

Predictability of intraocular lens calculation and early refractive status: the Infant Aphakia Treatment Study

OBJECTIVE

To report the accuracy of intraocular lens (IOL) power calculations and the early refractive status in pseudophakic eyes of infants in the Infant Aphakia Treatment Study.

METHODS

Eyes randomized to receive primary IOL implantation were targeted for a postoperative refraction of +8.0 diopters (D) for infants 28 to 48 days old at surgery and +6.0 D for those 49 days or older to younger than 7 months at surgery using the Holladay 1 formula. Refraction 1 month after surgery was converted to spherical equivalent, and prediction error (PE; defined as the calculated refraction minus the actual refraction) and absolute PE were calculated. Baseline eye and surgery characteristics and A-scan quality were analyzed to compare their effect on PE.

MAIN OUTCOME MEASURES

Prediction error.

RESULTS

Fifty-six eyes underwent primary IOL implantation; 7 were excluded for lack of postoperative refraction (n = 5) or incorrect technique in refraction (n = 1) or biometry (n = 1). Overall mean (SD) absolute PE was 1.8 (1.3) D and mean (SD) PE was +1.0 (2.0) D. Absolute PE was less than 1 D in 41% of eyes but greater than 2 D in 41% of eyes. Mean IOL power implanted was 29.9 D (range, 11.5-40.0 D); most eyes (88%) implanted with an IOL of 30.0 D or greater had less postoperative hyperopia than planned. Multivariate analysis revealed that only short axial length (<18 mm) was significant for higher PE.

CONCLUSIONS

Short axial length correlates with higher PE after IOL placement in infants. Less hyperopia than anticipated occurs with axial lengths of less than 18 mm or high-power IOLs. Application to Clinical Practice Quality A-scans are essential and higher PE is common, with a tendency for less hyperopia than expected.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00212134.

Comparison of anterior segment measurements with rotating Scheimpflug photography and partial coherence reflectometry

PURPOSE

To compare central corneal thickness (CCT), anterior chamber depth (ACD), and keratometry (K) readings measured using optical low-coherence reflectometry (OLCR) biometry and high-resolution rotating Scheimpflug photography.

SETTING

Eye Hospital of Wenzhou Medical College, Wenzhou, China.

DESIGN

Comparative case series.

METHODS

The CCT, ACD endothelium to lens, ACD epithelium to lens, and K (mean; in flattest meridian; in steepest meridian) were measured 5 times using the LenStar/Biograph OLCR biometer and 3 times with the Pentacam Scheimpflug system in eyes of healthy volunteers. Concordance was evaluated using paired t tests, the Pearson correlation, and Bland-Altman analyses.

RESULTS

The CCT, ACD endothelium to lens, and ACD epithelium to lens measured with the Scheimpflug system were slightly, albeit significantly, higher than with the OLCR biometer (P<.05); the respective 95% limits of agreement (LoA) were -8.2 μm to 15.7 μm, -0.11 to 0.15 mm, and -0.13 to 0.17 mm. However, the Scheimpflug system gave significantly flatter readings for K in the flattest meridian (95% LoA, -0.54 to 0.32 diopters [D]), K in the steepest meridian (95% LoA, -0.63 to 0.45 D), and mean K (95% LoA, -0.53 to 0.33 D) (P<.001). The CCT, ACD, and K readings were all highly correlated between the 2 devices (r >0.95, P<.001).

CONCLUSIONS

The CCT and ACD measurements with the OLCR biometer and Scheimpflug system can be used interchangeably in healthy young subjects. However, for K measurements, these devices have wide LoA so may not be interchangeable under certain clinical circumstances.

Comparison of intraocular lens power calculation formulae in pediatric eyes

PURPOSE

To evaluate accuracy of intraocular lens (IOL) power calculation formulae (SRK II, SRK/T, Holladay 1, Hoffer Q) in pediatric eyes.

DESIGN

Retrospective case series.

PARTICIPANTS

One hundred thirty-five eyes of 96 children with congenital, developmental, or acquired cataracts who underwent uncomplicated cataract surgery and IOL implantation by a single surgeon over a 10-year period.

METHODS

Axial length (AL), keratometry (K), and manufacturer's A constant were employed in 4 common IOL power calculation formulae to predict the refractive outcome. Retinoscopy was measured at 4 to 8 weeks postoperatively and converted to spherical equivalent. For analysis, eyes were grouped by age at surgery, AL, and mean K.

MAIN OUTCOME MEASURES

We determined the prediction error (PE) = predicted refraction - actual refraction and the absolute PE = |predicted refraction - actual refraction|. The formula that gave the best prediction (minimum PE) was determined.

RESULTS

The mean age at surgery was 6.4 years. Mean absolute PE was 1.11 for the SRK II, 0.84 for SRK/T, 0.76 for Holladay, and 0.76 for Hoffer Q formulae. There was a trend toward greater PE in eyes of younger children (< or =2 years), shorter AL (AL < or = 22 mm) and steeper corneas (mean K > 43.5 diopters [D]). On comparing absolute PE obtained with 4 formulae in each patient, Hoffer Q gave the minimum PE in 46% of eyes compared with 23% with SRK II, 18.5% with SRK/T, and 12.5% with Holladay 1. The SRK/T, Holladay 1, and Hoffer Q were similar in accurately predicting refractive error within +/-0.5 D in about 43% eyes. When clinically significant deviation in PE occurred (>0.5 D), there was usually an undercorrection (72%), except for Hoffer Q, which was almost as likely to overcorrect as undercorrect (44% vs 56%). The PE was lower with office measurements when compared with anesthesia measurements, owing probably to better fixation in older children with higher ALs.

CONCLUSION

The PE was insignificant (PE < or = 0.5 D) in 43% eyes, and similar for all formulae. However, the Hoffer Q was predictable for the highest number of eyes. When the PE was >0.5 D, most formulae gave an undercorrection, except for the Hoffer Q, which the surgeon may want to consider when targeting postoperative refractions.

Corneal power measurements in fixating versus anesthetized nonfixating children using a handheld keratometer

PURPOSE

To compare keratometry measurements on a fixating patient with readings from the same nonfixating patient intraoperatively using the Nidek KM-500 handheld keratometer.

METHODS

Consecutive patients who were scheduled for strabismus or nasolacrimal surgery between 5 and 11 years of age were included in the study. Handheld keratometry was performed preoperatively on both eyes with the child fixating and intraoperatively with the child anesthetized. Three readings were taken on each eye. The steepest and flattest corneal meridians were recorded. Intraclass correlation coefficients were calculated to assess reliability, and interchangeability was assessed by the use of the Bland-Altman method.

RESULTS

Included in the study were 55 eyes of 28 patients. The average fixating keratometry reading was 44.10 +/- 1.45 D for right eyes and 44.12 +/- 1.42 D for left eyes. The average nonfixating keratometry reading was 44.06 +/- 1.62 D for right eyes and 44.02 +/- 1.54 D for left eyes. The intraclass correlation coefficient for the average keratometry obtained fixating versus nonfixating was 0.96 for right eyes and 0.95 for left eyes. The Bland-Altman analysis showed fairly large limits of agreement between readings, but most readings fall within the limits of variability. The mean time to obtain the intraoperative measurements was 4.26 minutes.

CONCLUSIONS

In our study the Nidek KM-500 handheld keratometer provided reliable readings when used intraoperatively on anesthetized nonfixating children and required minimal time to perform.