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G. Iribarren, R. Iribarren, M. Torres, I. G. Morgan, F. Choudhury, R. Varma; Lens Power in an Adult Population: The Los Angeles Latino Eye Study. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1717. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To study the crystalline lens power in older adults without cataract in relation to refractive error.
A subset of participants from a population-based study, the Los Angeles Latino Eye Study, consisting of only those aged 61-70 years with nuclear opacity grading 0 and I (i.e.: without clinical cataract) was studied. This selection was performed to concentrate on persons after age-related hyperopic shifts had occurred, but before there were myopic shifts associated with nuclear cataract. The ocular components were measured by A-scan and the lens power was calculated with Bennett’s formula. The correlation coefficients between the components of refraction and mean values for each ocular component were determined for three refractive groups. Myopes were participants with spherical equivalent < -0.50 diopters, hyperopes were those with spherical equivalent > +1.00 diopters and the rest were considered emmetropes.
There were 452 participants in the 61-70 age range with nuclear opacity grading of 0 and 1. Men comprised 39.8%. Refractive groups differed in axial length and anterior chamber depth, but not in corneal power. Lens thickness was significantly lower in myopes when compared to emmetropes (4.35 +/- 0.39 mm vs. 4.50 +/- 0.49 mm, p = 0.048). There were negative correlations between calculated lens power and axial length (r = -0.531, p < 0.001), and between lens power and refractive error (r = -0.080, p =0.08). This produces a paradox, because less powerful lenses were associated simultaneously with longer eyes and with more hyperopic refractions. The mean lens power was lower in hyperopes when compared to emmetropes (23.27 +/- 2.02 diopters vs. 23.94 +/- 2.24 diopters respectively, p = 0.013).
These results confirm the existence of a paradox first noted by Olsen et al. (Acta Ophth Scan 2007;85:361-6) of negative correlations of lens power with axial length and refractive error. This is explained because hyperopic eyes have lower lens power than emmetropes.
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