Having a low HbA1c reduces the risk of diabetic retinopathy but doesn't eliminate it completely. Duration of diabetes is a major risk factor and the majority of people with Type 1 have background retinopathy within 20 years of diagnosis. Someone with poor glucose control might have developed it within 5 years.
Although we can't alter the duration of diabetes, there are other risk factors which can be controlled e.g. keeping blood pressure low, having a good lipid profile, not smoking. Have a look at the page noblehead suggests, it is a good quality source of information.
Bear in mind that background retinopathy does not affect your sight and does not need treatment. Although it does tend to progress with time, having good control of glucose, BP and cholesterol will make it likely that any progression would be slow. Many people have background retinopathy for many years without progressing to sight-threatening retinopathy.
The best advice is to make sure you address any modifiable risk factors you may have and to attend screening regularly so that if any sight-threatening changes do occur, you can be referred promptly and offered treatment, if necessary. Treatment is most effective before symptoms develop. Obviously, if you do develop any sight problems, you need to get them checked immediately and not wait for your next screening appointment.