In those cases the thin lens formula by Bennett and Rabbetts 14 can be used instead. 12 This method produces power values similar to those with phakometry 13 but requires knowledge of lens thickness, which is not always available in clinical practice. One such approach is Bennett's formula, 11 which calculates the equivalent lens power based on ocular biometry and refraction, assuming that the lens is similar to that of the Gullstrand-Emsley model eye.

9, 10 But since these devices are not available commercially, other indirect approaches for estimating lens power have been proposed. There is an indirect method called phakometry, however, that determines the radii of curvature by analyzing the location and relative sizes of the Purkinje reflections. In vivo assessment of the lenticular power, on the other hand, is challenging due to the position of the lens inside the eye, which impedes measuring its power directly. While this finding fundamentally concurs with previous in vivo studies, it is at odds with studies performed on donor eyes that reported lens power increases after the age of 55. This in vivo study showed a monotonous decrease in crystalline lens power with age, with a steeper decline after 55 years. The correlation of lens power with different refractive components was statistically significant for axial length ( r = −0.523, P 0.05). The highest crystalline lens power was found in emmetropic eyes and eyes with a short axial length. The average lens power showed a statistically significant decrease as a function of age, with a steeper rate of decrease after the age of 55. The study included 1069 Caucasian subjects (490 men, 579 women) with a mean age of 44.2 ± 14.2 years and mean lens power of 24.96 ± 2.18 diopters (D). Lens power was calculated using the modified Bennett-Rabbetts method, using biometry data from an autorefractometer, Oculus Pentacam, and Haag-Streit Lenstar. One randomly selected eye per subject was used. To observe the age-related changes in crystalline lens power in vivo in a noncataractous European population.ĭata were obtained though Project Gullstrand, a multicenter population study with data from healthy phakic subjects between 20 and 85 years old.

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