Study: Risk Factors for Axial Elongation Not Modifiable

Although there is a link between decreased annual axial length growth and age, the risk factors for elongation may not be modifiable for adults with high myopia, a study published in JAMA Ophthalmology shows. According to researchers, preventing myopia may be the best approach to reduce the prevalence of pathologic myopia.

Researchers examined the medical records of 15,745 patients. Among the 1877 patients with 9161 visits included in the analysis, the mean age was 62.10±12.92 years, and 1357 (72.30%) were women. The mean axial length was 29.66±2.20 mm with a mean growth rate of 0.05±0.24 mm per year. Among the 9161 visits, 7096 eyes (77.46%) had myopic maculopathy and 2477 eyes (27.04%) had choroidal neovascularization (CNV). 

The odds ratio for inducing a severe elongation of the axial length was 1.46 (95% CI, 1.38-1.55) for women, 0.44 (95% CI, 0.35-0.56) to 0.63 (95% CI, 13 0.50-0.78) for patients older than 40 years, and 1.33 (95% CI, 1.15-1.54) for those with a best-corrected visual acuity (BCVA) worse than 20/400. “Our results showed that a BCVA of 20/400 was associated with the highest risk for axial elongation when compared with BCVA of better than 20/60,” the research explains. “Because the refractive error and axial length were not matched, we believe that the emmetropic process may lead to axial elongation. This may also explain the increased axial length among eyes with BCVA of worse than 20/60.”

The report also shows the odds ratio for inducing a severe elongation of the axial length of 1.67 (95% CI, 1.54-1.81) to 2.67 (95% CI, 2.46-2.88) for patients with a baseline axial length of 28.15 mm or greater. Additionally, the presence of maculopathy had an odds ratio for inducing a severe elongation of the axial length of 1.06 (95% CI, 0.96-1.17) to 1.39 (95% CI, 1.24-1.55), and 1.37 (95% CI, 1.29-1.47) for prior CNV. 

“Although the pathogenesis of CNV-related macular atrophy is not fully determined, mechanical stress at and around the scarred CNV may be associated with the enlargement of the hole in Bruch membrane that is commonly found in CNV-related macular atrophy,” according to investigators. “Prior CNV and subsequent CNV-related macular atrophy may result in a greater increase of the axial length in this group with poor BCVA.”

This study’s limitations include the possibility of prior measurement biases. Also, only 30% of eyes had a definite staphyloma, and the presence of concomitant abnormalities, such as amblyopia or glaucoma were not analyzed.

Reference

Du R, Xie S, Igarashi-Yokoi T, et al. Continued increase of axial length and its risk factors in adults with high myopia. JAMA Ophthalmol. Published online August 26, 2021. doi:10.1001/jamaophthalmol.2021.3303