Abstract
Purpose: :
Lens thickness may have implications for visual functions over a lifetime: emmetropization, the development of juvenile myopia, and presbyopia. We evaluated sagittal crystalline lens thickness from 3 months to 35 years of age.
Methods: :
We combined sagittal lens thickness measurements from the baseline visit of our three longitudinal studies:• the Berkeley Infant Biometry Study (BIBS) a cohort study of 302 infants aged 3 months;• the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) a seven-year study of 4929 children aged 5 -15 years; and• the Study of the Progression of Adult Nearsightedness (SPAN), a five-year cohort study of 396 myopic adults aged 25-35 years.All lens thickness measurements were made using A-scan ultrasound; through a closed eyelid for infants and by corneal contact for the children and adults. Cross-sectional data from the baseline visit of each study are presented.
Results: :
The mean crystalline lens thickness at 3 months was 3.91 ± 0.16 mm. From infancy through 10 years there was a progressive thinning of the crystalline lens by about 50 µm per year to a minimum thickness of 3.42 ± 0.16 mm. Between the ages of 10 and 15, the lens differed by about 10 µm per year. The lens thickness differed in adults by about 20 µm per year. Extrapolating from the linear regression of the SPAN data, the lens would return to the sagittal lens thickness found in infancy (3.91 mm) at the age of 40 years.
Conclusions: :
The U-shaped function for lens thickness and age indicates that at least two processes determine sagittal lens thickness. It is well-established that the lens continues to grow by adding cell layers throughout life. In young children, increasing cell layer thickness is likely offset by a stretching of the lens from growth of the globe. After adolescence, when axial and equatorial eye growth is complete, the additional fibers contribute to a continual increase in sagittal lens thickness.
Keywords: clinical (human) or epidemiologic studies: natural history • refractive error development • accomodation