Consultant Ophthalmologist,
Cataract & Refractive Surgeon

BMedSci BM BS MRCS MRCSEd MRCOpth FRCOphth MMedLaw PgD Cataract & Refractive Surgery

Clinically Significant Macula Oedema (CSMO)

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What's going on?

The patient has diabetic maculopathy that has reached a threshold for laser treatment. There is oedema and/or exudates very close to the fovea, and if these changes persist or worsen the vision will be permanently compromised. Large studies have indicated that this situation requires laser retinal photocoagulation to prevent visual loss. Once vision has been lost, laser treatment is seldom able to restore it – the emphasis is on prevention.

If I examine the patient, what will I find?

Changes such as haemorrhages and/or exudates at, or very close to, the fovea.

What if I've diagnosed it?

Refer urgently via letter.

What will the hospital do?

Apply argon laser photocoagulation to the area of leaky retina. This procedure is called a macular grid because a regular grid of laser is applied to the macula. Only mild burns are required to alter the blood-retinal barrier, but they do reduce vision in the area where they are applied. If the laser is inadvertently applied to the fovea, the central vision will be damaged. Sometimes the exudates surround a focal leaking microaneurysm (dot haemorrhage) in a circular (circinate) pattern. Laser may be applied focally to the centre of the circinate to dry it up.

What do I need to do?

Optimisation of diabetic and blood pressure control is required.

What to tell the patient

They have a severe problem with their retina related to their diabetes and need laser treatment to preserve their sight. If the condition is left unchecked their vision will get worse.

Problems that may arise, and how to deal with them

Sometimes the macular oedema is related to capillary occlusion, resulting in an ischaemic maculopathy. This is not amenable to treatment.