Anterior eye differences by myopia severity

Paper title: Anterior segment structural changes across myopia severity and their association with myopia progression: A large-scale clinical analysis

Authors: Du H (1), Deng B (2), Cao Y (3)

1. Department of Ophthalmology, Luzhou People's Hospital, Luzhou, China.
2. Department of Ophthalmology, The Fushun People's Hospital, 490 Jixiang Road, Fushi Street Zigong, Fushun 643200, Sichuan Province, PR China.
3. Department of Ophthalmology, The Affiliated Hospital of Southwest Medical University, Luzhou, China.

Date: Published online January 14, 2026

Reference: Du H, Deng B, Cao Y. Anterior segment structural changes across myopia severity and their association with myopia progression: A large-scale clinical analysis. Photodiagnosis Photodyn Ther. 2026 Feb; 57:105352.

[Link to open access paper]

Axial length is the most widely studied structural marker of myopia, but how other anterior segment features vary with severity or relate to progression remains less well understood. This retrospective study aimed to clarify those associations by analysing anterior segment characteristics in a large cohort of patients with varying degrees of myopia.

The study included 4,392 patients aged 17 to 58 years who underwent myopia correction surgery in China. Based on spherical equivalent refractive error, eyes were categorised as low myopia (0 to –3.00D), moderate myopia (–3.00 to –6.00D), or high myopia (worse than –6.00D).

Key points were as follows:

• Axial length, intraocular pressure, anterior chamber volume, and corneal curvature values all increased with higher myopia severity.
• Corneal diameter and dark-adapted pupil diameter decreased with increasing myopia.
• The vertical component of the Kappa angle (Ky) increased progressively and was strongly associated with myopia severity.
• White-to-white corneal diameter and anterior chamber depth also showed significant correlations with myopia level.
• Central corneal thickness varied across groups but was not linearly associated with myopia severity.
• Logistic regression identified Ky and white-to-white corneal diameter as the most influential factors in myopia severity models.

This study highlights that myopia severity is associated with structural changes in the anterior segment, but translating these findings into clinical care must be done with caution. While axial length remains the key metric for monitoring progression, many practitioners lack access to biometry or anterior segment imaging. More accessible parameters like white-to-white corneal diameter (WTW) may seem appealing, as smaller WTW was associated with greater severity and potentially progression risk—but WTW is a stable anatomical feature, and we currently cannot use its absolute value as a sole predictor of progression risk in children.

The vertical component of the Kappa angle (Ky) also showed a strong association with myopia severity, with each 1 mm decrease linked to a meaningful reduction in myopia severity risk. However, Ky measurement is not widely available, and no clinical cut-offs exist to guide interpretation.

Other structural differences included higher central corneal thickness (CCT), flatter corneal curvature, and increased intraocular pressure (IOP) in more myopic eyes. These may reflect broader biomechanical changes in the eye with increasing severity. While not immediately actionable, they offer useful context for understanding the anatomical profile of progressive and higher myopia and may inform future clinical tools or decision-making frameworks.

This study adds to our understanding of how the anterior segment changes across myopia severity, but many of the associations observed remain exploratory. It is unclear, for example, whether increased intraocular pressure in higher myopes reflects a true structural difference or is simply affected by higher central corneal thickness measurements. The link between flatter corneal curvature and greater severity may reflect biomechanical shape, but how this relates to risk of progression remains unknown.

The strong association between vertical Kappa angle (Ky) and linearly increasing level of myopia is intriguing, particularly the finding that each 1 mm decrease in Ky was linked to a meaningful reduction in severity. However, the mechanism behind this relationship is speculative, and it remains to be seen whether Ky is a meaningful structural marker of risk, and whether it reflects underlying mechanisms that could be clinically relevant.

This was a retrospective, cross-sectional study involving adults aged 17 to 58 years who were undergoing refractive surgery. As such, the findings may not apply to paediatric patients, where myopia onset and progression are most active and clinically relevant. Myopia progression was not tracked - instead, myopia severity was used as a proxy for progression, rather than being assessed through longitudinal follow-up.

Future studies could include prospective, longitudinal designs in younger age groups to determine whether these structural parameters -particularly Ky, corneal diameter, and anterior chamber structure changes - can meaningfully predict and help identify children at greater risk of myopia progression.

Objective: This study aims to investigate the variations in anterior segment parameters among patients with different degrees of myopia and explore their impact on myopia progression.

Methods: A retrospective analysis was conducted on ocular parameters of 4392 patients who underwent myopia correction surgery at the affiliated hospital of Southwest Medical University from January 2019 to January 2023. The patients were categorized into mild, moderate, and high myopia groups based on the severity of their myopia. Measurements of corneal thickness (CCT), intraocular pressure (IOP), axial length (AL), steep corneal curvature (Ks), flat corneal curvature (Kf), white-to-white corneal diameter (WTW), pupil diameter under bright conditions (LPD), pupil diameter under dark-adapted conditions (DPD), corneal volume (CV), anterior chamber volume (ACV), anterior chamber depth (ACD), and Kappa angle values (Kx and Ky) were performed and analyzed using SPSS 28.0 software.

Results: Significant differences were observed in most of the aforementioned parameters among patients with different degrees of myopia. With increasing myopia severity, CCT, IOP, AL, Ks, Kf, CV, ACV, ACD, and Ky exhibited a gradual increase (all P < 0.05), while WTW and DPD showed a gradual decrease (all P < 0.05). Kx and LPD did not exhibit statistically significant differences (P > 0.05). Correlation analysis revealed significant positive correlations between IOP and the degree of myopia (OR = 1.02, P = 0.005), WTW and the degree of myopia (OR = 0.47, P < 0.001), ACV and the degree of myopia (OR = 1.01, P < 0.001), and significant negative correlations between ACD and the degree of myopia (OR = 0.83, P = 0.031). Ky showed a significant positive correlation with the degree of myopia (OR = 2.55, P < 0.001). These findings provide further evidence of the association between ocular parameters and myopia progression.

Conclusion: Significant differences exist in anterior segment parameters among patients with varying degrees of myopia, which may be related to myopia progression. Further investigation into the relationship between these parameters and the development of myopia will contribute to a better understanding of the underlying mechanisms and provide a theoretical basis for scientific myopia prevention and control.

[Link to open acces paper]