What happens if you start losing your vision due to diabetes? In this second part of his article, highly experienced consultant ophthalmologist Mr Alistair Laidlaw explains how diabetic retinopathy is diagnosed and treated.
How is it diagnosed?
Most patients with diabetic retinopathy, certainly in the UK, are diagnosed as having it through the national screening programme. We have a very effective one, one of the first in the world up and running, and we've been at it longer than most. Diabetics are meant to have their eyes photographed every year, so most diabetics are found through that NHS activity. It can also be identified as part of routine diabetic care by a general practitioner or a diabetic physician.
Unfortunately, some people do have it diagnosed at a point when they've suffered one of the complications, be it blurred vision or a haemorrhage in the eye. And that's unfortunate because it would often have been good to have identified it earlier, as treatment in diabetic retinopathy not only aims to improve lost vision, which you can do to an extent, but a lot of what we do aims to prevent loss of vision or prevent ongoing loss of vision once it's been lost.
How is it treated?
There are several mainstays to the treatment of diabetic retinopathy. The thing that's easy to forget, because it's not done by an ophthalmologist and is quite hard work, is to improve diabetes control. For patients with type II diabetes, I'm afraid that often means losing a substantial amount of weight, changing one's diet, and making sure that blood pressure is good. But losing weight gets blood pressure down, as well as improves diabetic control. It's just that we all know it's very hard to do, so general medical care has to be part of it.
What ophthalmologists can do is based on observation, because sometimes things haven’t reached the threshold for treatment and are being watched until they cross the line in the sand. At which point when people have crossed the line, treatment is broadly divided into two groups, it's either injection therapy or laser.
Injection therapy is used for proliferative disease, and the growth of new blood vessels, but mainly for maculopathy, the swelling of the retina in the centre of the eye. Maculopathy will involve a course of injections to try and dry out the retina and improve the vision. By drying out the swollen retina, you improve the vision as much as can be improved. If the retina is damaged, it can only go back to its best potential, which is why a pre-emptive strike is much better than playing catch-up. However, injection therapy unfortunately, can be quite costly and can go on for a long period. Most of the drugs used in injection therapy fit into the group of the anti-VEGF agents, with well-known trade names like Avastin, Eylea, and Lucentis. Those drugs tend to be given initially monthly, to lengthen out. There's a bit of titration of effect against the interval. Again, this is mainly for maculopathy. It's also possible to use steroid injections in the eye, and there's a little pellet that can be injected, which can last up to about four months rather than monthly. But unfortunately, there are definite side effects with cataracts and glaucoma associated with that, so it's not considered the first-line treatment.
The second way in which one can treat diabetic retinopathy is with a laser. For proliferative disease, there's a bit of a debate going on, but in terms of cost, effectiveness, and safety, I think most people are saying that scatter laser photocoagulation (applying the laser to the retina) is the best way to treat new vessel growth. It's quite a contentious area at the moment, but I think that's still the way that is probably best for most patients. In terms of maculopathy, the laser has a definite role if the centre of the retina, the swollen area, called diabetic macular oedema.
Then injection therapy is almost always the best option. But in other cases, carefully picking off some little leaking areas in the retina with a laser can be a very good and very long-acting treatment. The problem with the injections is that they only last one, maybe four months, something in that range whereas laser treatment is effectively a lifelong treatment.
If you think you may be experiencing vision loss caused by diabetes or would like more information, you can schedule a consultation on Mr Laidlaw’s Top Doctors profile.