I agree it's a bit of a jump to two years, however, it depends on the context. Assuming we're talking about diabetic retinopathy, then if I've not had any indication of retinopathy and I have a "good" A1c through the year, then it's unlikely I will need another scan. If after 2 years some retinopathy is found despite good A1c, then it will be early stage anyways and they can get on and treat it.
The economics of public healthcare is monstrously complex and they've just increased the budget for closed loop systems (CLS) for (some) diabetics by £14 million. Somewhere in that giant excel file there will be a formula showing how the new CLS recipients are less likely to need retinal scans and hence fewer scans and ...a saving of over £14 million. Or some such justification.