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The eyes - ‘a window to diabetes complications’

3rd March 2022

Dr Kevin Fernando, GP Partner and Educational Supervisor, North Berwick Health Centre, and Scottish Lead of the Primary Care Diabetes Society, shared some tips on detecting diabetic eye problems – and related issues – at the Society’s recent conference.

Dr Fernando began his presentation with this key message: “A person with diabetes complaining of acute or subacute onset of floaters, flashes, blurred vision or field loss should always be taken seriously and considered for urgent referral.” These symptoms could signal serious eye disease, such as diabetic maculopathy. The macula is responsible for central vision and diabetic maculopathy is the commonest cause of blindness in diabetes. And it can occur at any stage of diabetic retinopathy. “It’s a misconception that maculopathy is always associated with more severe diabetic retinopathy,” he warned. Another eye complication which may give rise to the symptoms above is vitreous haemorrhage; this can occur in proliferative retinopathy, because the new blood vessels that are formed are friable and may bleed. 

The swinging light test

What can be done in primary care to pick up any signs of serious eye pathology in people with diabetes? There is the swinging light test, which picks up a defect in the pupil indicative of serious optic nerve or retinal eye disease. “I think this is something that is realistic for us, as GPs and nurses and pharmacists, to do in primary care,” Dr Fernando said. “It’s quite straightforward and quick to do.” Put simply (and details are readily available online) the test involves swinging a light source, such as a bright torch, from side to side in front of the patient, so that it passes each eye in turn. “The pupil would normally constrict when the light is shone into it. So, if it dilates instead, that could signify serious underlying retinal or optic nerve disease,” he explained. 

Links to other diabetes complications.

Diabetic kidney disease often goes hand in hand with diabetic retinopathy, so it is worth checking for this too if the patient has eye symptoms. And not everyone with diabetes has diabetic kidney disease – they may have another kidney condition, such as nephrotic syndrome or glomerulonephritis. Also, diabetic kidney disease is normally associated with longer duration of diabetes. So if someone has chronic kidney disease, but short duration of diabetes, look for other causes. For instance, heavy proteinuria suggests nephrotic syndrome, while haematuria suggests glomerulonephritis – rather than diabetic kidney disease – underlying any chronic kidney disease.

And, finally, diabetic retinopathy is also strongly indicative of underlying cardiac autonomic neuropathy (CAN). “This is something we tend not to appreciate in primary care, but it is strongly associated with reduction in life expectancy, for 25-50% of those with CAN will die within five to ten years,” said Dr Fernando. This realisation has changed his own practice. “Now, in any of my patients where I get a report back of significant changes in diabetic retinopathy, I’m actively looking of symptoms and signs of CAN.” The most common sign is resting tachycardia. “Just check the pulse. Is it over 90? That might suggest underlying CAN. Is there evidence of postural hypotension? Do an ECG and see if there are pathological Q waves, suggestive of a silent myocardial infarction.” He further recommends taking a history to see if the individual describes exercise intolerance. If they have had a recent operation, did the anaesthetist report any cardiac instability? “These are all signs of underlying CAN,” he said. In summary, a problem with the eyes may signal complications elsewhere – and prompt detection in primary care may improve the long-term outlook for the person with diabetes.  

Any opinions expressed in this article are the responsibility of the EASD e-Learning Programme Director, Dr Eleanor D Kennedy.