If you are diabetic, your retina needs looking at once a year

What sugar does to the retina

Years of raised blood glucose weaken the walls of the tiny vessels feeding the retina. They leak, they bleed, and the retina responds by growing fragile new vessels that bleed more. Fluid collecting at the centre of the retina, called macular oedema, is the usual reason vision drops. None of this hurts, and by the time you notice a change the easy window has often passed.

What the screening involves

A dilated examination is the core of it, supported by imaging where it adds something.

• Visual acuity: a baseline to compare against next year
• Dilated fundus examination: the whole retina, including the edges where changes start
• Retinal photography: a dated image, so next year is a comparison and not a fresh guess
• OCT: cross sectional imaging that measures fluid at the macula
• Pressure check: diabetes raises glaucoma risk too

How often

At least once a year from the time you are diagnosed with diabetes, whether or not your vision has changed. More often if changes have already been found, if your control has been poor, or if you are pregnant, because pregnancy can accelerate retinopathy quickly.

Come sooner than your annual visit if

You see new floaters or a shower of black spots, a curtain or shadow across part of your vision, sudden blurring, or straight lines that look bent. Those are not things to note down for next year.

What we will ask you

How long you have had diabetes, your most recent HbA1c or sugar readings, your blood pressure, your kidney status if you know it, and what medication you are on. Bring the numbers. Retinal risk tracks them closely and it changes how often you need to be seen.

Questions people ask about this