Prediction of CW chord as a measure for the eye's orientation axis after cataract surgery from preoperative IOLMaster 700 measurement data

Distribution of angle alpha and angle kappa offsets among adult candidates for cataract surgery

PURPOSE

The current study aimed to describe the distribution of angle alpha and angle kappa offsets as well as their associated ocular biometric parameters in a large population of candidates for cataract surgery.

METHODS

This cross-sectional retrospective study included 8,119 eyes of 4,781 candidates for cataract surgery (mean age 70.7 ± 12.9 years). There were 49.9% right eyes, and 53.0% patients were females. The angles offset and ocular biometric parameters were measured by the IOLMaster 700 (Carl Zeiss Meditec, AG, Germany).

RESULTS

Patient's age and gender, and most of their ocular biometric measurements were similar for the right and left eyes except for pupil diameter (4.01 ± 1.18 vs. 3.92 ± 1.14 mm, respectively, P < 0.001). The angle alpha offset magnitude was similar for the right and left eyes (0.50 ± 0.20 and 0.51 ± 0.21 mm, P = 0.08), whereas the angle kappa offset magnitude was greater in the right eyes (0.37 ± 0.21 vs. 0.33 ± 0.20 mm, P < 0.001). The angle kappa offset magnitudes were greater in the right eyes compared to the left eyes for both males (0.36 ± 0.21 vs. 0.33 ± 0.21 mm, respectively, P < 0.001) and females (0.37 ± 0.20 vs. 0.34 ± 0.20 mm, respectively, P < 0.001). The offset magnitudes of both angles varied significantly according to gender, eye laterality, angle location, and biometric parameters (e.g., axial length). The offset magnitudes of both angles were positively correlated in both right and left eyes.

CONCLUSIONS

The offset magnitudes of both the angle alpha and angle kappa present significant variations according to gender, eye laterality, angle location, and biometric parameters, such as AL. These values are also population-specific.

Prediction of IOL decentration, tilt and axial position using anterior segment OCT data

BACKGROUND

Intraocular lenses (IOLs) require proper positioning in the eye to provide good imaging performance. This is especially important for premium IOLs. The purpose of this study was to develop prediction models for estimating IOL decentration, tilt and the axial IOL equator position (IOLEQ) based on preoperative biometric and tomographic measures.

METHODS

Based on a dataset (N = 250) containing preoperative IOLMaster 700 and pre-/postoperative Casia2 measurements from a cataractous population, we implemented shallow feedforward neural networks and multilinear regression models to predict the IOL decentration, tilt and IOLEQ from the preoperative biometric and tomography measures. After identifying the relevant predictors using a stepwise linear regression approach and training of the models (150 training and 50 validation data points), the performance was evaluated using an N = 50 subset of test data.

RESULTS

In general, all models performed well. Prediction of IOL decentration shows the lowest performance, whereas prediction of IOL tilt and especially IOLEQ showed superior performance. According to the 95% confidence intervals, decentration/tilt/IOLEQ could be predicted within 0.3 mm/1.5°/0.3 mm. The neural network performed slightly better compared to the regression, but without significance for decentration and tilt.

CONCLUSION

Neural network or linear regression-based prediction models for IOL decentration, tilt and axial lens position could be used for modern IOL power calculation schemes dealing with 'real' IOL positions and for indications for premium lenses, for which misplacement is known to induce photic effects and image distortion.

Repeatability of biometric measures from the IOLMaster 700 in a cataractous population

PURPOSE

The purpose of this study was to investigate the repeatability of biometric measures and also to assess the interactions between the uncertainties in these measures for use in an error propagation model, using data from a large patient cohort.

METHODS

In this cross-sectional non-randomised study we evaluated a dataset containing 3379 IOLMaster 700 biometric measurements taken prior to cataract surgery. Only complete scans with at least 3 successful measurements for each eye performed on the same day were considered. The mean (Mean) and standard deviations (SD) for each sequence of measurements were derived and analysed. Correlations between the uncertainties were assessed using Spearman rank correlations.

RESULTS

In the dataset with 677 eyes matching the inclusion criteria, the within subject standard deviation and repeatability for all parameters match previously published data. The SD of the axial length (AL) increased with the Mean AL, but there was no noticeable dependency of the SD of any of the other parameters on their corresponding Mean value. The SDs of the parameters are not independent of one another, and in particular we observe correlations between those for AL, anterior chamber depth, aqueous depth, lens thickness and corneal thickness.

CONCLUSIONS

The SD change over Mean for AL measurement and the correlations between the uncertainties of several biometric parameters mean that a simple Gaussian error propagation model cannot be used to derive the effect of biometric uncertainties on the predicted intraocular lens power and refraction after cataract surgery.

Angle Kappa and angle Alpha agreement between Pentacam Scheimpflug system, swept source optical coherence tomography and ray-tracing aberrometry

PURPOSE

To compare the consistency of Pentacam Scheimpflug system (Pentacam® HR), ray-tracing aberrometry (iTrace), and swept source optical coherence tomography (IOLMaster 700) measurements for Angle Kappa and angle Alpha.

METHODS

A prospective randomized cohort study. 86 individuals (86 eyes) aged 19-45 years with best corrected vision of 4.9 or better were randomly selected from January 2022 to December 2022 in a tertiary-level hospital. Angle Kappa and angle Alpha were measured or calculated using Pentacam, iTrace, and IOLMaster 700, respectively.

RESULTS

The mean difference of angle Kappa between any two instruments was not statistically significant, but the mean difference of angle Alpha between both Pentacam and iTrace, Pentacam and IOLMaster 700, and iTrace and IOLMaster 700 was statistically significant (p value <0.001, 0.003, <0.001). The highest consistency of angle Kappa and the narrowest 95% LoA (-0.20 to 0.21) were found between Pentacam and iTrace according to Bland Altman plots, but between Pentacam and IOLMaster 700 according to Mountain plots. Both Bland Altman plots and Mountain plots showed the highest consistency of angle Alpha and the narrowest 95% LoA (-0.14 to 0.24) between Pentacam and iTrace.

CONCLUSION

The mean angle Kappa among Pentacam® HR, iTrace, and IOLMaster 700 had good agreement, and the value of angle Kappa could be output directly, making it more convenient for clinical application. The measured or calculated angle Alpha had poor agreement, and ophthalmologists could refer to measurements from multiple instruments.