Lens Power in a Population-Based Cross-Sectional Sample of Adults Aged 40 to 64 Years in the Shahroud Eye Study

Abstract

There was an unexpected biphasic pattern of the distribution of lens power with age in this cross-sectional study. Younger subjects were taller, and despite having longer axial lengths, their bigger eyes were still predominantly emmetropic. The greater axial lengths were counterbalanced by both lower corneal and lower lens powers.

Distribution of the Crystalline Lens Power In Vivo as a Function of Age

“…32 Similarly, Olsen et al 29 mentioned that the cataract in some of their subjects may have influenced their lens power values. Finally, in Atchison et al, 28 Iribarren et al, 30 and the current study, all subjects with cataractous lenses were excluded, which could be why these studies showed a power decrease after the age of 60. Note that the studies above are all cross-sectional rather than longitudinal, which implies that the results may have been influenced by gradual changes within the cohorts used.…”

“…This course is in contrast with the literature, where Glasser and Campbell, 5 as well as Borja et al, 7 reported an increase in lens power after the age of 50 to 60, 5,7 Jones et al, 23 and Atchison et al 28 found a monotonous linear decrease, and Olsen et al 29 reported no correlation between lens power and age between 55 and 100 years of age. Finally, Iribarren et al 30 even reported a very mild increase and subsequent decrease in lens power in Iranian subjects between 40 and 64 years of age. From this overview of the literature we find that, although most of these articles confirm that lens power changes with age and that the rate of this change somehow alters between the age of 50 and 60, in vitro and in vivo studies seem to disagree on the exact course of this altered rate of change (Fig.…”

“…Olsen et al 29 used a variation of the Olsen IOL formula 31 on data from noncyclopleged Icelandic subjects between 55 and 100 years old, 29 while Atchison et al 28 performed phakometry on noncyclopleged subjects, Iribarren et al 30 applied the Bennett formula to data of middle-aged Iranian subjects after cycloplegia, and finally the Bennett-Rabbetts formula applied to noncyclopleged Caucasian subjects aged between 20 and 85 years was used in this study. Given the advanced age of the Olsen et al subjects and the cycloplegia of the Iribarren et al data, the influence of accommodation can be excluded from these two data sets.…”

Active Maintenance of the Gradient of Refractive Index Is Required to Sustain the Optical Properties of the Lens

“…However, in adulthood only the lens continues to grow and the aging of the lens has been associated with a gradual shift toward hyperopia in unaccommodated lenses that occurs over many decades. 63 This hyperopic shift is due to a gradual loss of lens power, which is due primarily to a flattening of the GRIN that has been attributed by some research groups to a compaction of deeper lying fiber cells by the continued addition of new fiber cells at the lens equator. 63 In some individual this age-dependent loss of lens power is abruptly disrupted by a rapid myopic shift often referred to as second sight as the resultant increase in lens power restores near vision.…”

“…63 This hyperopic shift is due to a gradual loss of lens power, which is due primarily to a flattening of the GRIN that has been attributed by some research groups to a compaction of deeper lying fiber cells by the continued addition of new fiber cells at the lens equator. 63 In some individual this age-dependent loss of lens power is abruptly disrupted by a rapid myopic shift often referred to as second sight as the resultant increase in lens power restores near vision. Unfortunately, in these individuals this period of improved ''second sight'' is closely followed by the onset of nuclear cataract 64 Our ouabain experiments suggest a physiological explanation for this phenomenon.…”