Patients with diabetes frequently report changing visual acuities when their glucose levels are chronically high. Which of the following could explain the fluctuating acuity with high blood glucose levels?

Fluctuating levels of sugars and sugar alcohols in the lens can cause fluctuating visual acuity. With high blood glucose, there would be increased levels of sorbitol in the lens. The lens does not contain mitochondria and cannot use the TCA cycle/electron transport chain to generate energy. Galactitol causes the same problems as sorbitol, but galactitol is derived from galactose, whereas sorbitol is produced from glucose. The patient has high glucose levels, so galactitol would not be expected to accumulate in the lens. Macular degeneration affects the retina, but in this case, it is the lens that is the affected tissue. Reducing fructose levels in the lens would reduce sorbitol levels, which would ease the visual acuity problem, not make it occur.