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

Agreement between IOLMaster 700 and Pentacam AXL for IOL power measurement in patients with high myopia

PURPOSE

The anterior segment in individuals with high myopia has different features compared to those without myopia. IOLMaster 700 and Oculus Pentacam AXL are two accurate optical biometers. Both devices measure the cornea differently and thus yield different results when measuring intraocular lens (IOL) power. The purpose of this study is to assess the agreement of the IOL power calculation between IOLMaster 700 and Oculus Pentacam AXL in patients with high myopia.

METHODS

A prospective, analytical cross-sectional study was conducted to assess the agreement between the IOL power calculation with IOLMaster 700 and Oculus Pentacam AXL. In this study, 44 eyes were examined using Oculus Pentacam AXL and IOLMaster 700, and IOL power was calculated using the Barret Universal II formula and the AMO Sensar AR40E. The Bland-Altman plot was used to evaluate the agreement between the two devices.

RESULTS

Based on the IOLMaster 700 examination, 44 eyes with high myopia had axial lengths ranging from 26.05 to 34.02 mm. The mean IOL power was 8.26 ± 4.755 and 8.58 ± 4.776 based on IOLMaster 700 and Oculus Pentacam AXL, respectively. The Bland-Altman plot revealed good agreement between the two devices, with a mean difference of -0.3182 in the IOL power calculation and a 95% LoA of 0.88099-0.24462 with a 95% confidence interval.

CONCLUSION

Both devices showed good agreement in the IOL power calculation in patients with high myopia.

Total and simulated keratometry measurements using IOLMaster 700 and Pentacam AXL after small incision lenticule extraction

PURPOSE

Calculating the intraocular lens (IOL) in patients after corneal refractive surgery presents a challenge. Because an overestimation of corneal power in cases undergone this surgery leading to a subsequent under-correction of IOL power. However, recent advancements in technology have eliable measurement of total corneal power. The aim of this research was to assess the agreement in simulated keratometry (SimK) and total keratometry (TK) values between IOLMaster 700 and Pentacam AXL.

METHODS

The study involved 99 patients (99 eyes) undergone small incision lenticule extraction (SMILE) surgery. Each patient underwent scans using IOL Master 700 and Pentacam AXL. The following parameters were recorded: SimK1, SimK2, Total K1 (TK1), and Total K2 (TK2) for IOLMaster 700; and SimK1, SimK2, True Net Power (TNP) K1, TNPK2, Total Corneal Refractive Power (TCRP) K1, and TCRP K2 for Pentacam AXL. Agreement between the two devices was evaluated using Bland-Altman plot, while paired t-test was utilized to compare any differences in the same parameter by both instruments.

RESULTS

The results revealed a strong correlation between the two devices.Noticeable comparability was identified for all SimK variables. However, there were noticeable differences in TK measurements as well as TK1-TNPK1, TK2-TNP K2, TK1-TCRP K1, and TK2-TCRP K2 parameters when comparing the two devices. The IOLMaster 700 consistently measured steeper values than the Pentacam AXL, with significant and clinically relevant differences of 1.34, 1.37, 0.87, and 0.95 diopters, respectively.

CONCLUSION

While there was a noticeable correlation between the IOLMaster 700 and Pentacam AXL in SimK measurements, a marked difference was noted in TK values. The two devices cannot be used interchangeably when quantifying TK values.

Agreements' profile of Scheimpflug-based optical biometer with gold standard partial coherence interferometry

AIM

To determine the agreement of ocular biometric indices including axial length, keratometric readings, anterior chamber depth, and horizontal corneal diameter between the Pentacam AXL and IOL Master 500.

METHODS

The study was a large cross-sectional population-based study (Tehran Geriatric Eye Study) conducted from Jan 2019 to Jan 2020. A total of 160 clusters were randomly selected proportional to size (each cluster contained 20 individuals) from 22 strata of Tehran city. All people aged 60y and above were invited to participate in the study. For all participants, preliminary ocular examinations were performed including the measurement of uncorrected and best-corrected visual acuity, objective and subjective refraction, anterior and posterior segment examinations. All participants underwent an ocular biometry using the Pentacam AXL and IOL Master 500.

RESULTS

The 95% limits of agreement (LoA) between the two devices were -0.13 to 0.19, -0.15 to 0.17, and -0.13 to 0.19 in normal, pseudophakic, and cataractous eyes, respectively. With increasing the axial length, the difference between the two devices significantly increased in all three groups of normal, pseudophakic, and cataractous eyes (P<0.001). The 95% LoAs between the two devices regarding the mean keratometry shows that the best LoAs were seen in cataractous (-0.33 to 0.81) and followed by normal eyes (-0.36 to 0.86) and the pseudophakic eyes (-0.48 to 0.90) had the widest LoA. The 95% LoAs for horizontal corneal diameter measurements were -0.08 to 0.86, -0.03 to 0.83, and -0.07 to 0.87 in normal, pseudophakic, and cataractous eyes, respectively. The 95% LoAs of anterior chamber depth measurements between the two devices was -0.39 to 0.19 and -0.37 to 0.13 in normal eyes and cataractous, respectively.

CONCLUSION

The Pentacam AXL has excellent agreement with the gold standard, IOL Master 500 in measuring axial length. In eyes with cataracts, the difference between the two devices is more scattered. With the increasing of axial length, the difference between the two devices increased, which should be considered when using Pentacam AXL.

The Current Burden and Future Solutions for Preoperative Cataract-Refractive Evaluation Diagnostic Devices: A Modified Delphi Study

Purpose

To obtain consensus on the key areas of burden associated with existing devices and to understand the requirements for a comprehensive next-generation diagnostic device to be able to solve current challenges and provide more accurate prediction of intraocular lens (IOL) power and presbyopia correction IOL success.

Patients and Methods

Thirteen expert refractive cataract surgeons including three steering committee (SC) members constituted the voting panel. Three rounds of voting included a Round 1 structured electronic questionnaire, Round 2 virtual face-to-face meeting, and Round 3 electronic questionnaire to obtain consensus on topics related to current limitations and future solutions for preoperative cataract-refractive diagnostic devices.

Results

Forty statements reached consensus including current limitations (n = 17) and potential solutions (n = 23) associated with preoperative diagnostic devices. Consistent with existing evidence, the panel reported unmet needs in measurement accuracy and validation, IOL power prediction, workflow, training, and surgical planning. A device that facilitates more accurate corneal measurement, effective IOL power prediction formulas for atypical eyes, simplified staff training, and improved decision-making process for surgeons regarding IOL selection is expected to help alleviate current burdens.

Conclusion

Using a modified Delphi process, consensus was achieved on key unmet needs of existing preoperative diagnostic devices and requirements for a comprehensive next-generation device to provide better objective and subjective outcomes for surgeons, technicians, and patients.

Accuracy of Intraocular Lens Power Calculation Based on Total Keratometry in Patients With Flat and Steep Corneas

PURPOSE

To analyze the accuracy of the current intraocular lens power calculation formulas using standard keratometry (K) and total keratometry (TK) data in patients with flat and steep corneas.

DESIGN

Retrospective consecutive cross-sectional study.

METHODS

An optical biometer with swept-source optical coherence tomography was used in this retrospective study. The standard deviation (SD), mean absolute error (MAE), median absolute error (MedAE), and the proportion of eyes with prediction error (PE) within ±0.25 diopter (D), ±0.5 D, ±0.75 D, and ±1.00 D were calculated to evaluate the refractive outcomes of each formula.

RESULTS

A total of 231 eyes from 231 patients were included. In the entire study cohort, the Emmetropia Verifying Optical (EVO) formula using TK data showed the lowest SD (0.383) and MAE (0.30) and the highest percentage of cases with a PE within ±0.5 D (81.4%). In the flat keratometry group, the EVO (P = .042), Haigis (P = .043), Hoffer Q (P = .038) and Holladay 1 (P = .013) formulas using TK data had significantly lower SD than using K data. The EVO formula using TK data showed the lowest SD (0.357) and MAE (0.28). In the steep keratometry group, the Hoffer Q (P = .036) and SRK/T (P = .029) formulas using TK data had significantly lower SD than using K data. The BUII TK formula showed the lowest SD (0.431), MedAE (0.26), and MAE (0.32).

CONCLUSION

The TK data set showed a better trend of refractive outcomes, especially in the flat and steep keratometry groups. EVO (TK) and BUII TK formulas were suggested for eyes with K values lower than 42 D and K values higher than 46 D, respectively.

Comparison of Intraocular Lens Power Calculation between Standard Partial Coherence Interferometry-Based and Scheimpflug-Based Biometers: The Importance of Lens Constant Optimization

Purpose

To compare the intraocular lens (IOLs) power calculated with Haigis, Hoffer Q, Holladay 1, and SRK/T formulas between the IOLs Master 500 and Pentacam AXL according to the lens status.

Methods

In this cross-sectional study, sampling was done in subjects above 60 years living in Tehran using multi-stage cluster sampling. All participants underwent optometric examinations including the measurement of visual acuity and refraction as well as slit-lamp biomicroscopy to determine the lens status. Biometric measurements and IOLs power calculation were done using the IOL Master 500 and Pentacam AXL. The order of imaging modalities was random in subjects. IOL power calculation was done according to optimized ULIB constants for the Alcon SA60AT lens. The IOL power was calculated according to a target refraction of emmetropia in all subjects.

Results

After applying the exclusion criteria, 1865 right eyes were analyzed. The mean IOL difference between the two devices was -0.33 ± 0.35, -0.38 ± 0.39, -0.41 ± 0.43, and -0.51 ± 0.43 according to the SRK/T, Holladay, Hoffer Q, and Haigis formulas, respectively. The Pentacam calculated larger IOL power values in all cases. The 95% limits of agreement (LoA) between the two devices for the above formulas were -1.01 to 0.35, -1.14 to 0.39, -1.25 to 0.43, and -1.35 to 0.33, respectively. The best LoA were observed in normal lenses for all formulas. The difference in the calculated IOL power between the two devices using the four formulas had a significant correlation with axial length, mean keratometry reading, and anterior chamber depth. According to the results of the four formulas, mean keratometry reading had the highest standardized regression coefficient in all formulas.

Conclusion

Although the difference in the calculated IOL power between IOL Master 500 and Pentacam AXL is not significant clinically, the results of these two devices are not interchangeable due to the wide LoA, especially for the Haigis formula; therefore, it is necessary to optimize lens constants for the Pentacam.

Comparison of optical low coherence interferometry and Scheimpflug imaging combined with partial coherence interferometry biometers in cataract eyes

PURPOSE

The purpose of the study was to evaluate the agreement between measurements by optical low-coherence interferometry (OLCI, Aladdin) and those by Scheimpflug imaging combined with partial coherence interferometry (Scheimpflug-PCI, Pentacam AXL) in cataract patients.

METHODS

This was a retrospective comparative study conducted in the United Arab Emirates. Axial length (AL), corneal power (keratometry, K), anterior chamber depth (ACD), and corneal astigmatism in patients with cataracts were measured with both devices. Difference and correlation were evaluated with paired t-test (p) and Pearson's correlation coefficient^®, respectively.

RESULTS

A total of 164 eyes of 95 patients were analyzed (164 eyes for K, 155 for ACD, and 112 for AL). The mean AL taken by OLCI was longer than that by Scheimpflug-PCI (23.25 mm vs. 23.23 mm, P ≤ 0.0001), showing an excellent correlation between the two (r = 0.9990). ACD measured by OLCI was 0.08 mm shallower than that by Scheimpflug-PCI (P = 0.0003, r = 0.7386). Corneal power measured by OLCI was lower than that by Scheimpflug-PCI (differences in mean K, flat K, and steep K were 0.05 diopters (D), 0.08 D, and 0.02 D, respectively), showing very strong correlations between the two devices (r = 0.9614, 0.9445, and 0.9535, respectively). Only flat K values measured with the two devices were significantly different (P = 0.0428). There were no statistically significant differences in the magnitude of astigmatism or J45 vector between the two devices (P = 0.1441 and P = 0.4147, respectively). However, J0 vector values were significantly different (P = 0.0087).

CONCLUSION

Although OCLI and Scheimpflug-PCI showed strong correlations for measurements of AL, K, ACD, and corneal astigmatism in cataract patients, there were small but statistically significant differences in AL, ACD, flat K, and J0 vector. Thus, these two devices are not interchangeable for calculating intraocular lens power.

Distribution of White-to-White Corneal Diameter and Anterior Chamber Depth in Chinese Myopic Patients

Purpose: To investigate the distribution of white-to-white (WTW) corneal diameter and anterior chamber depth (ACD) in Chinese myopia patients. Methods: This was a cross-sectional observational study conducted at five ophthalmic centers. Anterior segment biometry was performed in 7,893 eyes of the 7,893 myopic patients using Pentacam, and the WTW and ACD were recorded. The distribution patterns of WTW and ACD were evaluated and the correlation between WTW and ACD was analyzed statistically. Results: There were 4416 (55.95%) males and 3477 (44.05%) females. The age of the study population was 25.14 ± 5.41 years. Distribution of WTW was slightly positively skewed (Skewness = 0.0076, Kurtosis = 0.3944, KS P = 0.020) with a mean of 11.65 ± 0.38 mm and a 95% normal range of 10.91-12.39 mm. A significant difference in WTW was found among different myopia groups (P < 0.001). The ACD was normally distributed (Skewness = 0.899, Kurtosis = 0.027, KS P = 0.086). The mean ACD was 3.25 ± 0.26 mm and the 95% normal range of was 2.74-3.75 mm. A significant difference in ACD was also found among different myopia groups (P = 0.030). There was a significant correlation between WTW and ACD (r = 0.460, P < 0.001). Conclusions: In our study, 95% of the Chinese myopic patients had a WTW within 10.91-12.39 mm and an ACD within 2.74-3.75 mm. ACD and WTW were significantly different among different myopia, gender and age groups. WTW was positively correlated with ACD.