The literature on the relationship between acetazolamide and stone formation indicates the following:
The incidence among patients being treated for glaucoma is unknown, since the number of reported cases is very small and the population at risk is usually undefined. My rough estimate is less than 1%.
The crystalline component of the stone is calcium phosphate.
There are no preventive measures, but it would be of interest to have plain films of the abdomen before and during the treatment. There may be a significant number of "silent" stones in addition to the "noisy" ones.