Mathematical Estimation of Axial Length Increment in the Control of Myopia Progression

Axial length association with corneoscleral sagittal height and scleral asymmetry

PURPOSE

To determine how corneoscleral geometry changes with axial length and to assess the usefulness of including the sagittal configuration of the anterior segment when predicting the axial length.

METHODS

An observational study was performed including 96 healthy subjects (96 eyes). Axial length was calculated from optical biometry (IOL Master 500). Corneal curvature and scleral sagittal height parameters at 13, 14 and 15 mm were obtained automatically using corneoscleral topography (eye surface profiler; ESP). In addition, corneal and scleral sagittal heights at numerous locations (21 radii: 0-10 mm from the corneal apex at 12 angles: 0-330°) were calculated using the raw height data extracted from the ESP. The relationships between axial length and the study parameters were analysed using Pearson correlation analysis. The equations for the prediction of axial length were obtained by fitting multiple linear regression models.

RESULTS

The temporal-nasal scleral asymmetry at 13-, 14- and 15-mm chord lengths was significantly correlated with axial length (r2 ≤ 0.26; p < 0.001). Significant inverse correlations were found between the temporal scleral sagittal height and axial length (r2 ≤ 0.28; p ≤ 0.02). The nasal scleral sagittal height was not associated with axial length. Three significant multiple linear regression models were fitted based on spherical equivalent, corneal radius and scleral asymmetry at 13 (r2 = 0.79; p < 0.001), 14 (r2 = 0.80; p < 0.001) and 15 (r2 = 0.80; p < 0.001) mm chord lengths.

CONCLUSIONS

Larger ocular globes show reduced temporal-nasal scleral asymmetry, mainly due to the lower sagittal height of the temporal sclera. Thus, the geometry of the temporal scleral may be a factor of interest during myopia progression.

New Frontiers in Myopia Progression in Children

Myopia is a growing public health issue, with projections indicating that half of the global population may be affected by 2050 [...].

Celebrating 25 Years of Optical Biometry: A Milestone in Ophthalmology

Optical biometry has fundamentally transformed cataract surgery, and 2024 marked 25 years since the introduction of the first optical biometer. In the early 1980 s, Fercher and colleagues pioneered the optical noncontact eye length measurement, leading to the first interferometric A-scan of the eye. This innovation, patented and later developed by Zeiss, culminated in the release of the IOLMaster in 1999, enabling more accurate and reproducible eye diagnostics. Over the years, optical biometry has evolved into advanced swept-source optical coherence tomography devices, accompanied by numerous formulas for calculating intraocular lens power. Today, this technology is crucial not only for cataract surgeries, especially in eyes previously treated with refractive surgery, but also in advancing our understanding of diseases across fields like cardiology and oncology.

The long and short of it: a comprehensive assessment of axial length estimation in myopic eyes from ocular and demographic variables

BACKGROUND/OBJECTIVES

Axial length, a key measurement in myopia management, is not accessible in many settings. We aimed to develop and assess machine learning models to estimate the axial length of young myopic eyes.

SUBJECTS/METHODS

Linear regression, symbolic regression, gradient boosting and multilayer perceptron models were developed using age, sex, cycloplegic spherical equivalent refraction (SER) and corneal curvature. Training data were from 8135 (28% myopic) children and adolescents from Ireland, Northern Ireland and China. Model performance was tested on an additional 300 myopic individuals using traditional metrics alongside the estimated axial length vs age relationship. Linear regression and receiver operator characteristics (ROC) curves were used for statistical analysis. The contribution of the effective crystalline lens power to error in axial length estimation was calculated to define the latter's physiological limits.

RESULTS

Axial length estimation models were applicable across all testing regions (p ≥ 0.96 for training by testing region interaction). The linear regression model performed best based on agreement metrics (mean absolute error [MAE] = 0.31 mm, coefficient of repeatability = 0.79 mm) and a smooth, monotonic estimated axial length vs age relationship. This model was better at identifying high-risk eyes (axial length >98th centile) than SER alone (area under the curve 0.89 vs 0.79, respectively). Without knowing lens power, the calculated limits of axial length estimation were 0.30 mm for MAE and 0.75 mm for coefficient of repeatability.

CONCLUSIONS

In myopic eyes, we demonstrated superior axial length estimation with a linear regression model utilising age, sex and refractive metrics and showed its clinical utility as a risk stratification tool.

Efficacy of the DRL orthokeratology lens in slowing axial elongation in French children

Background

This study aims to assess and compare the impact of Orthokeratology Double Reservoir Lens (DRL) versus Single Vision Lenses (SVL) on axial elongation and anterior chamber biometric parameters in myopic children over a 6- and 12-month treatment period in France.

Methods

A retrospective study involving 48 patients aged 7 to 17 years, who underwent either orthokeratology treatment or single-vision spectacle correction, was conducted. Changes in refractive error, axial length, and anterior chamber depth were examined.

Results

Twenty-five patients comprised the Orthokeratology (OK) group, while twenty-three were in the control group (single-vision spectacle group). Significant increases in mean axial length were observed over time in both the control (0.12 ± 0.13 mm and 0.20 ± 0.17 mm after 6 and 12 months, respectively; F (2,28.9) = 27.68, p < 0.001) and OK groups (0.02 ± 0.07 mm and 0.06 ± 0.13 mm after 6 and 12 months, respectively; F (2,29.1) = 5.30, p = 0.023). No statistically significant differences in axial length were found between male and female children (p > 0.620). Age-specific analysis revealed no significant axial elongation after 12 months in the 14-17 years group in the OK group. Anterior biometric data analysis at 6 and 12 months showed statistical significance only for the DRL group.

Conclusion

Orthokeratology resulted in an 86 and 70% reduction in axial elongation after 6 and 12 months of lens wear, respectively, compared to the single-vision spectacles group. Myopia progression was more pronounced in younger children, underscoring the importance of initiating myopia control strategies at early ages.

Assessment of the Clinical Effectiveness of DRL Orthokeratology Lenses vs. Single-Vision Spectacles in Controlling the Progression of Myopia in Children and Teenagers: 2 Year Retrospective Study

The purpose of this study was to assess the effect of orthokeratology treatment with DRL lenses on the control of myopia progression compared with single vision glasses users (monofocal glasses). It was also possible to analyze the clinical efficacy of orthokeratology treatment with DRL lenses for myopia correction in children and adolescents in a 2 year retrospective, multicenter study, performed in eight different ophthalmology centers in France. A total of 360 data records of children and adolescents with myopia between -0.50 D and -7.00 D at baseline visit, who completed treatment and had a centered outcome, were selected for the study from a database of 1271. The final sample included subjects undergoing orthokeratology treatment with DRL lenses (n = 211 eyes) and spectacle wearers (n = 149 eyes). After one year of treatment, the data analysis shows that the DRL lens has a refractive myopia progression control rate of 78.5% compared with the spectacle wearers (DRL M change = -0.10 ± 0.25 D, p < 0.001 Wilcoxon test and Glasses M change = -0.44 ± 0.38 D, p < 0.001 Wilcoxon test). Similar results were found after 2 years of treatment (80% with 310 eyes). This study showed the clinical efficacy of orthokeratology DRL lenses compared to monofocal spectacle wearers in controlling myopia progression in children and adolescents in a 2 year retrospective study.

Key Factors in Early Diagnosis of Myopia Progression within Ocular Biometric Parameters by Scheimpflug Technology

The aim of this study was to evaluate the relationship between myopia and ocular biometric variables using the Pentacam AXL^® single rotation Scheimpflug camera. This prospective, cross-sectional, single-center study was performed in fifty Caucasian patients aged between 18 and 30 years (24.84 ± 3.04 years). The measured variables included maximum and minimum keratometry (K1 and K2, respectively), anterior chamber depth (ACD), corneal horizontal diameter or white to white (WTW), central corneal thickness (CCT), corneal asphericity (Q), and axial length (AXL). The tomographic and biometric measurements were considered optimal when the quality factor was greater than 95% according to the manufacturer's software instructions. The AXL presented a significant correlation with the spherical equivalent without cycloplegia (SE without CP), age at onset of myopia (r = -0.365, p = 0.012), mean keratometry (Km) (r = -0.339, p = 0.016), ACD (r = 0.304, p = 0.032), and WTW (r = 0.406, p = 0.005). The eyes with AXL higher than 25 mm had earlier onset; higher SE without CP, AXL, and Q; and a flatter Km. AXL is the biometric variable with the greatest influence on the final refractive state in the adult myopic eye. Ophthalmologists and optometric management must consider these biometric differences in order to identify the most appropriate correction techniques in each case. The use of the Pentacam AXL in ocular biometric measurement is effective, reproducible, and non-invasive.

Effect of corneal stiffness decrease on axial length elongation in myopia determined based on a mathematical estimation model

Purpose: To investigate the relationship between the corneal material stiffness parameter stress-strain index (SSI) and axial length (AL) elongation with varying severities of myopia, based on a mathematical estimation model. Methods: This single-center, cross-sectional study included data from healthy subjects and patients preparing for refractive surgery in the Qingdao Eye Hospital of Shandong First Medical University. Data were collected from July 2021 to April 2022. First, we performed and tested an estimated AL model ( A L M o r g a n ) based on the mathematical equation proposed by Morgan. Second, we proposed an axial increment model ( Δ A L ) corresponding to spherical equivalent error (SER) based on A L e m m e t r o p i a ( A L M o r g a n at SER = 0) and subject's real AL. Finally, we evaluated the variations of Δ A L with SSI changes based on the mathematical estimation model. Results: We found that AL was closely associated with A L M o r g a n (r = 0.91, t = 33.8, p < 0.001) with good consistency and SER was negatively associated with Δ A L (r = -0.89, t = -30.7, p < 0.001). The association of SSI with AL, A L e m m e t r o p i a , and Δ A L can be summarized using the following equations: A L = 27.7 - 2.04 × S S I , A L e m m e t r o p i a = 23.2 + 0.561 × S S I , and Δ A L = 4.52 - 2.6 × S S I . In adjusted models, SSI was negatively associated with AL (Model 1: β = -2.01, p < 0.001) and Δ A L (Model 3: β = -2.49, p < 0.001) but positively associated with A L e m m e t r o p i a (Model 2: β = 0.48, p < 0.05). In addition, SSI was negatively associated with Δ A L among subjects with AL ≥ 26 mm (β = -1.36, p = 0.02). Conclusion: AL increased with decreasing SSI in myopia.