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Kathryn Richdale, Loraine T. Sinnott, Peter A. Wassenaar, Petra Schmalbrock, Chiu-Yen Kao, Mark A. Bullimore, Karla Zadnik; Uncovering the Effects of Age and Accommodation on the Human Eye through Imaging. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2229. doi: https://doi.org/.
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To evaluate age-related changes in vivo in the accommodative system of a cohort of emmetropic human adults.
The right eyes of 26 emmetropic adults, aged 30 - 50 years, were examined using ultrasound, phakometry, keratometry, anterior segment optical coherence tomography, and 7T magnetic resonance imaging. The eye was imaged with increasing accommodative demands from 0 to 6 D, in 2 D increments, and under cycloplegia. Regression and mixed model analyses were used to assess ocular changes with age and accommodation.
Age was associated with greater lens thickness [3.67 + 0.031 x (Age - 30), p < 0.001], steeper anterior lens curvature [11.82 - 0.11 x (Age - 30), p = 0.001], shallower anterior chamber depth [3.85 - 0.029 x (Age - 30), p < 0.001] and lower equivalent refractive index of the lens [1.457 - 0.001 x (Age - 30), p = 0.002]. Accommodative response was associated with greater lens thickness (3.67 + 0.065 x Response + 0.032 x (Age - 30), p < 0.001), shorter lens equatorial diameter (8.76 - 0.075 x Response, p < 0.001), smaller ciliary body ring diameter (11.60 - 0.068 x Response, p < 0.001) and anterior thickening and commensurate posterior thinning of the ciliary body (Thickness at 1 mm = 0.765 + 0.013 x Response; Thickness at 2 mm = 0.498 - 0.011 x Response; Thickness 3 mm = 0.282 - 0.015 x Response; all locations posterior to the scleral spur, p < 0.01). Age did not moderate the effect of accommodation on ciliary body thickness.
The overall size and shape of the lens are altered with both accommodation and age. The ciliary muscle continues to contract in a consistent fashion per diopter of accommodation across ages, suggesting that ciliary muscle function is undiminished until at least the fifth decade. Understanding morphological changes in the accommodative system with age will allow the development of better treatment options for presbyopia.
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