I suffer from bg swings as well

I fought for years to get the Dexcom through the NHS funding but with no success. I'm now waiting for the new release of the Libre, which I really hope is going to be soon. The Libre doesn't have alarms as the Dexcom but at least is more affordable and should help preventing some of my swings that are definitely harmful for the retina. Another cool innovation I can suggest about retinopathy treatment/prevention is the Noctura 400 by PolyPhotonix:
http://noctura.com/ The Noctura 400 is a mask worn at night during the sleeping hours and it works by preventing dark adaptation hence retinal hypoxia by emitting a soft green glow. It's available through selected optometrists who check the condition of the retina every 3 months. I'm using this sleep mask and trying to spread the word on this forum about it as I think that more people should be aware of such a non-invasive alternative to fear less going to the eye screenings.