What could have caused cataract for 57+ f having controlled bp (with medicine) & sugar levels (diet only) ?

Aging or diabetes: Every year there are a dozen or more patients in my practice with cataracts in their 50's that need surgery. Even though cataracts are more common in older age groups, some people get them at a younger age for unknown reasons. Diabetics in general get cataracts at an earlier age than the general population. It is thought that with wide swings in blood sugar that the lens becomes damaged.

Cataracts: Cataracts can occur from the following factors: aging, genetics, steroid use, poor diet, trauma, previous eye inflammation, cumulative sunlight exposure, and they can be congenital: from birth.