My reference to current restrictions regarding Covid-19 was because I am aware that many NHS appointments are limited, currently, to those considered most urgent.
If you are concerned that you should be seen more frequently, (and with your history that is not, in my opinion, unreasonable) it may be wise to seek another opinion from a different optician if your current one won’t see you. I find that my local independent optician gives continuity of care. With same members of staff having been there for many years. I do get the free eye sight test every 12 months, as there are relatives with glaucoma. I would pay for that myself if it didn’t come free of charge. The NHS retinopathy test I have been getting annually at the local NHS centre. Ladt year I was informed that for people like me, with no diabetic complications or changes, it would probably be every two years in future.
I hope you get the result you seek. Best of luck.