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E. A. Knighton, R. K. Zoltoski, D. K. Roberts, J. T. Wilensky, J. R. Kuszak; Increase in Lens Thickness as Measured by A-Scan Ultrasonography in an Older African-American Population. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4591.
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We create dynamic computer models to recreate anatomical relationships at the fiber level in the lens during growth and accommodation. To do this accurately, gross lens dimensions are necessary to increase the accuracy of the model. We hypothesize that lens thickness (LT) as measured by A-scan ultrasonography will increase, but at a lesser rate with age.
Sixty-four African-American subjects between the ages of 50 and 82 underwent pre-dilation A-scan ultrasonography (PalmScanTM AF2000) recording of both eyes as controls for a separate study of glaucoma. Linear regression (Systat v11) of age and LT (mm) of the right eye was used to assess the increase in LT across age (µm/year).
During the ages assessed, the lens is in the stage of forming a 15-branch to 18-branch complex star suture. The initial linear regression analysis divided the ages into 15 year spans (<65, n = 23, > 65, n =41) to account for changes in growth. An increase in LT of 55±21 µm/year (<65, p = 0.015) and 60±15 µm/year (>65, p<0.001) was noted. Although this analysis was significant, the smaller sample size resulted in higher variability. Since the slope of the lines was similar, the increase in LT across the age span was considered to be constant. Therefore, the data was collapsed and analyzed across the entire group. Above the age of 50, an increase in LT of 31±6 um/year of age was determined (LT = 0.031 (±0.006) * age+2.842 (±0.422), R = 0.532, p < 0.001), which is a greater increase than the reported values of 13 - 29 µm/year between the ages of 20 and 60 using various methods.
The rate of lens growth may not slow as much as expected with age. A-scan ultrasonography is the usual method for determining LT; however, its reported resolution of 100 um may limit its use in smaller sample sizes. Further analysis of more lenses in each decade of life is warranted to provide accurate growth rate assessment for lens aging in an older population.
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