Quasielastic light scattering study of the living human lens as a function of age
Purpose. To determine contributions of molecular scattering elements to the increase with age in the light scattered from the human ocular lens in vivo. Methods. We used quasielastic light scattering to measure autocorrelation functions of the intensity of light scattered in vivo from three locations (anterior, nuclear and posterior) along the optic axis in ocular lenses of 225 subjects, ranging from 17 to 63 years of age. We deduced probability distributions of key parameters (I(s), I(f), I(i), I(T)), which describe contributions of slowly diffusing (I(s)), rapidly diffusing (I(f)) and relatively immobile (I(i)) scattering elements to the total light intensity (I(T)) scattered into the collection optics. We deduced characteristic times τ(s), and τ(f) that describe the Brownian motion of scattering elements. Results. Probability distributions for each age decile show clearly defined shifts in key parameters with age. I(T) at the nucleus increases by a factor of three from age 20 to 60 years. This increase is produced principally by an approximate fivefold increase in I(s). I(T) and I(s) and can be detected with an accuracy of ~ ± 10%. We estimate threshold values for I(T), which mark the boundary beyond which clinical cataract becomes manifest. This boundary represents 6 to 8 times the light scattering efficiency expected from the newborn lens. Conclusions. This methodology permits a sensitive, quantitative, clinically useful representation of the pre-cataractous molecular changes associated with aging in the living human lens.
Thurston, GM; Hayden, DL; Burrows, P; Clark, JI; Taret, VG; Kandel, J; Courogen, M; Peetermans, JA; Bowen, MS; Miller, D; Sullivan, KM; Storb, R; Stern, H; Benedek, GB
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