Diabetes and the damage you cannot feel

If you have diabetes, your eyes need examining every year whether or not anything seems wrong. This is one of the few pieces of eye-health advice that is genuinely unconditional, and the reason is that the disease most likely to take your sight produces no symptoms while it is still treatable.

What the retina has to do with blood sugar

The retina is lined with very fine blood vessels. Persistently raised glucose damages their walls. They begin to leak, to close off, and to bleed. The retina, starved of blood supply, responds by growing new vessels — and the new ones are fragile, bleed into the eye, and pull on the retina as the scaffolding around them contracts.

That sequence is diabetic retinopathy, and it runs for years without the patient noticing. There are no pain fibres in the retina. Peripheral damage does not affect the sharp central vision you use to read, so acuity can stay perfect while a substantial area is already affected.

By the time vision changes — a sudden shower of floaters from a bleed, a distorted or missing patch in the centre, a general dimming — the disease is advanced. Treatment at that stage is about salvage.

Why this matters here

Diabetes is increasing across Nigeria, and a large proportion of people who have it do not yet know. Many are diagnosed years after the disease began, which means the retina has already had those years of exposure. Retinopathy is among the commonest causes of working-age sight loss.

There is also a diagnostic role that runs the other way: the retina is the only place in the body where blood vessels can be inspected directly, and optometrists not infrequently find the signs of diabetes in someone who came in for spectacles and did not know they had it.

What screening involves

The pupils are dilated with drops and the retina is examined, usually with photographs taken for comparison against future visits. It takes half an hour or so, plus a few hours of blurred near vision and light sensitivity afterwards. Arrange not to drive yourself home.

The comparison year on year is the valuable part. A single photograph shows the state of things; a series shows the direction, which is what decides whether to watch or to treat.

Treatment, and what it can and cannot do

Laser treatment can seal leaking vessels and stop abnormal ones from growing. Injections into the eye can reduce swelling at the macula. Surgery can clear blood and relieve traction on the retina. These work, and they work far better early.

None of them restores sight that has already been lost. This is why the screening is annual and not symptom-driven.

The part that is actually in your control

Glycaemic control is the single largest factor in whether retinopathy develops and how fast it advances. Large long-term trials are unambiguous on this. Blood pressure control matters substantially too, as does not smoking.

None of that is news to anyone living with diabetes, and it is not always easy. But it is worth knowing that the effort shows up in your eyes specifically, and that it is measurable there.

What to do now

If you have type 2 diabetes, have your eyes screened at diagnosis and then annually. If you have type 1, from about five years after diagnosis, then annually. If you are pregnant and diabetic, more often — pregnancy can accelerate retinopathy markedly, and you should be seen early in the pregnancy.

See someone urgently, not at your next appointment, if you develop a sudden increase in floaters, a curtain or shadow across your vision, or any sudden change in sight.

Every practitioner in the chapter's register can perform diabetic eye screening and will refer you where treatment is needed.