We evaluated the ability of Lensmeter 701 (LOM) to detect changes in the transparency of the lens graded with the Lens Opacities Classification System II (LOCS II). In this prospective study 410 middle-aged Eastern Finnish men participating in the Kuopio Atherosclerosis Prevention Study were examined three times at eighteen month intervals, and lens opacities were graded with both LOM and LOCS II, the latter serving as the standard.Majority of the change in the LOM reading during the follow-up fell within the 95% tolerance interval of the apparatus (3.08 units). Only four eyes showing progression by LOCS II were detected by LOM. The association between LOM change and the change observed by LOCS II was not statistically significant, and the correspondence of the two methods was weak. It seems that the sensitivity of the LOM is not sufficient to detect small changes in the transparency of the lens over time.