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Kristine E Lee, Barbara E K Klein, Ronald Klein, Mary Rechek; Ten-year changes in axial length in the Beaver Dam Eye Study.. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3421. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
While evidence suggests that refraction may change as adults age, there is limited information on the related characteristic of axial length in older adults. According to some evidence, axial length differs by age cross-sectionally, but little is understood about whether the globe changes as a person ages or if the age differences result from cohort effects. The purpose of this analysis is to examine changes in axial length measured at up to three time points in a ten-year period in adults over 60 years of age in the population-based Beaver Dam Eye Study.
Axial length (AL) was measured using partial coherence laser interferometry (IOL Master, Carl Zeiss, Germany) in adults between 58 and 100 years of age during examinations approximately five years apart between 2003 and 2016. The ten-year change in AL was calculated by subtracting the first measure from the last measure for the 1,601 eyes from 807 people with data at the 10-year follow-up. Axial length from the right eye across all visits was used to evaluate cohort effects using a linear regression model with age and year of birth categories. The cohort analysis included 4,384 person-visits (640 people had 1 visit; 696 had 2; and 784 had 3). All models were linear regression models with generalized estimating equations to account for multiple records from the same person.
The mean AL is longer in men and decreases with age from 23.9 mm in 58-64 year olds to 23.4 in 80+ year olds (decrease of 0.08 mm per 5 years of age, p<0.001, adjusting for gender) at the first examination. The 10-year change in AL ranges from -1.30 to 1.02 with mean (SD) change of 0.027 (0.111). A change > 0 indicates the axial length is longer at the follow-up visit. The change does not vary by sex (0.039 in F, 0.023 in M) but gets smaller with age, such that persons over the age of 75 years have slightly shorter AL at the follow-up visit (figure 1). Further, there appears to be a cohort effect, such that individuals of a similar age, but born more recently, have longer AL (figure 2). After accounting for year of birth, there are no longer significant differences in AL with age.
Axial length does not change much over time in adults over the age of 60 years, but may be getting shorter after the age of 75. The age differences observed in cross-sectional studies may largely be due to cohort effects and not actual aging changes.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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