Hi Maidz, I'm in exactly the same position as you. I got the letter through saying an appointment had been booked for me at the ophthalmology clinic. This happened a week and a half after my retinal scan. The important thing is, don't panic!
To be perfectly honest, I disregarded that rule and had a temporary breakdown. Then I calmed down, assessed the situation and rang the hospital. They couldn't give out any details over the phone, but a nurse there did run me through some possible scenarios. The first one was that the retinal screening wasn't clear enough, and the team doing the assessment wanted to get another photograph. The second one was that there was something there that needed some further looking into. I do have the early stages of retinopathy, so it's possible that it has progressed just enough to need further monitoring.
In my case, I think the latter is more likely. When the technician did my scan, I did get to look at the photograph. It looked like a good shot, and he was happy with the quality of the photo. However, I will also mention that from obsessive research a couple of years back, I know what retinopathy looks like in the scan. I didn't see anything horrifying on my picture. Obviously the people doing the assessment can use more in depth tools to check, but there definitely weren't any massive scars running the length of my retina.
After I got the panic out of my system, I have not felt the need to have a breakdown, and I will explain why. Retinal screening exists to catch problems at the very earliest stage. It is now incredibly rare for a diabetic to actually go blind. Generally speaking, doctors can preserve what sight a patient has at the time of treatment. So if you can see fine, then great! The chances are that if a problem has happened, it has been caught early enough that you will not need to worry about losing your vision.
Now, an important BUT springs in here. A diabetic who gets the early signs of problems, and then gets good diabetic control has little to fear. A poorly controlled diabetic who gets the early signs, has some treatment and then says 'well that's that' and carries on as before is asking for trouble. From what you have said, it seems like you are taking steps to make your diabetes control the best it can be. My advice is to do what I have done. Read, research and find ways to get blood sugars stable. It's not easy. My goodness do I know that. But it is very much possible. My advice is to go to YouTube and search for doctor troy stapleton. He is an Australian doctor who has type 1 diabetes, and talks about his ways of having excellent control. Jenny Ruhl's book 'diabetes 101' is also well worth reading. A lot of it is aimed at type 2s, but there's plenty of great information for us type 1s as well.
Getting back to the letter, the only thing we can do is wait and see. It could be as simple as a change of protocol, meaning a more in depth test is done every few years. If there is some treatment needed, then it's great that we are being offered what we need at the very earliest opportunity. Best of luck, and I hope in a few weeks we can both move on from a very routine appointment.