Glaucoma is an eye condition that can effect simply anyone of any age, (I know of a young child of 6 years old with Glaucoma) and it can effect anyone whether they have diabetes or not, though in the case of someone who has diabetes they are at a greater risk of developing this condition.
Glaucoma frequently takes years of slowly progressing before becoming noticed, though there are exceptions and one form of Glaucoma is known to come on rapidly within days.
I've suffered myself with Glaucoma for many years amongst several other eye problems, so I would advise anyone wheter they are diabetic or not, to get their eyes regularly examined by a competent optromitist, opticion or at a hospital eye clinic following on from a referal.
Glaucoma is held in control by various eye drops, and if found at its earlier stages of development can be treated sucessfully with these eye drops. Don't put off getting you eyes properly examined as damage caused by Glaucoma cannot be repaired.
Incidentally the regular checks that we diabetic get each year in the retinal scanning program is no garanteed way of checking for Glaucoma, and there isn't any substitute for also getting your eyes regularly checked at a properly qualified experienced opticians.