Prediction of axial elongation in adults with high myopia: the Wenzhou High Myopia Cohort Study

Identifying individuals at high risk of axial elongation is crucial for managing adults with high myopia, as further elongation substantially increases the risk of vision-threatening complications. This study aimed to identify the optimal predictors for axial elongation in this population.

This prospective cohort study enrolled 1025 eyes from 532 adults with high myopia (18-60 years). We evaluated the predictive performance of nine candidate variables for rapid axial elongation, defined as a 2-year axial elongation of at least 0.10 mm. Predictors were selected using bidirectional stepwise regression. Model discrimination was assessed using the area under the receiver operating characteristic curve (AUC), and the incremental value of the new model was quantified using integrated discrimination improvement (IDI).

The mean annual axial elongation rate was 0.020 ± 0.051 mm/year, and 24.78% of eyes developed rapid axial elongation. Stepwise regression constructed a full model (AUC = 0.811) including six predictors-age, sex, axial length, best-corrected visual acuity, choroidal thickness (ChT), and vascularity index. ChT showed the highest individual discriminative ability (AUC = 0.728), followed by age (AUC = 0.666). Removing age or ChT from the full model reduced the AUCs to 0.735 and 0.753, respectively (both P < 0.001), with IDIs of  - 0.116 and - 0.095 (both P < 0.001). In contrast, excluding sex only resulted in an IDI of - 0.008 (P = 0.032). Simplified models combining age and ChT, with or without sex, showed discrimination comparable to that of the full model, with only modest reductions in predictive performance (IDIs: -  0.028 and - 0.033, respectively; both P < 0.05). In the bivariate model, the predictive cut-off of ChT decreased progressively with age, ranging from 187 µm at age 20 to 29 µm at age 60. The results remained consistent in sensitivity analyses using alternative axial elongation definitions (0.05 mm and 0.15 mm). Nonlinear relationship analyses revealed that thinner choroids were associated with faster axial elongation rate only below an inflection point.

ChT and age are the optimal predictors for axial elongation in adults with high myopia. These findings establish their dominant role in personalized management and support further investigation into choroidal architecture to guide proactive, choroid-centered strategies.

This study was registered with the Chinese Clinical Trial Registry (ChiCTR2100047424).