Potential Negative Feedback between Age and Baseline Axial Length on Axial Elongation in High Myopia.

Purpose: To evaluate the axial elongation in highly myopic eyes and assess the effects of age, sex, baseline axial length (AL), cataract surgery (CS), pathologic myopia (PM), baseline intraocular pressure (IOP), and genetic risk scores (GRSs). Design: Retrospective cohort study. Participants: This study included 614 eyes from 367 individuals with high myopia. Methods: The study assessed axial elongation rates and their associations with age, sex, baseline AL, CS, PM, and baseline IOP including potential interactions among these factors. Additionally, the study examined whether incorporating GRS improved the predictive model for axial elongation. Main Outcome Measures: Axial elongation rate in highly myopic eyes. Results: The study included 367 participants (217 [59.1%] females, 150 [40.9%] males) with a mean age of 58.9 ± 14.4 years and a mean AL of 28.6 ± 2.0 mm. The mean follow-up duration was 4.7 ± 2.7 years, and the average axial elongation rate was 0.031 ± 0.030 mm/year. Cataract surgery was associated with significantly slower axial elongation (P < 0.001). Multivariate analysis revealed that axial elongation increased with age and baseline AL but decreased with CS and an age-AL interaction. The best-fitting model excluded GRS, thus achieving a lower Akaike information criterion score (-573.4) than models including GRS. Conclusions: Axial elongation persists in highly myopic eyes (0.031 mm/year) but slows over time, owing to baseline AL-age interactions. Genetic risk scores have limited predictive utility in adulthood. This highlights the need for further research on genetic and environmental determinants of myopia progression. Financial Disclosures: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.