The Relationship Between the Axial Length of the Eye and Age in Danish Adults

To describe the relationship between the axial length of the eye and age, and report reference values for axial length in a general adult European population.

As part of the epidemiological study FORSYN, the axial length in both eyes of a population-representative sample of 3,364 adult citizens (48.8% men, 51.2% women) was measured using swept-source optical coherence tomography. Approximately one third of the sample accepted the invitation (3,384 out of 9,708, 32.7%), and after correction for selection bias, multiple linear regression was used to estimate how the axial length depended on age in the whole population and among men and women. Based on the findings, reference values for the axial length in the adult population were calculated. Logistic regression was performed to examine whether the prevalence of axial lengths longer than or equal to 26.0 mm differed with age in both men and women.

The axial length showed no significant correlation with age (multiple linear regression, slope -0.002, 95% CI -0.005 to 0.0001, p = 0.06), but was significantly (unpaired t-test, p < 0.0001) longer in men (23.99 mm) than in women (23.53 mm). The axial length was longer than or equal to 26.0 mm in 3.8% (95% CI 3.4 to 4.2) of the adult population. There was no significant difference in age among participants with axial length above and below this value (logistic regression, OR = 1.00, p = 0.42).

Global reports of increased axial length in the younger demographic does not seem to apply to the general Danish population. When evaluating axial length, it should be considered that reference values differ among men and women.