Nonproliferative diabetic retinopathy (NPDR) consists of a range of clinical signs that confirm the onset of diabetes-associated retinal damage. Although most patients with NPDR do not require specific ocular treatment, regular review is required to allow prompt detection and/or treatment of Proliferative Diabetic Retinopathy (PDR, thought to result from retinal ischemia) or Diabetic Macular Edema (DME, related to leaking retinal vessels).
NPDR is usually asymptomatic.
The International Clinical Diabetic Retinopathy Disease Severity Scale grades NPDR as follows (see Diabetes –Introduction to Retinopathy, for explanation of terms):
- No apparent DR: no abnormalities visible.
- Mild NPDR: microaneurysms only.
- Moderate NPDR: more than ‘mild’, but less than ‘severe’.
- Severe NPDR: any of the following (‘the 4:2:1 rule’):
- 20 or more intraretinal haemorrhages in all 4 quadrants,
- venous beading in 2 or more quadrants, or
- prominent IRMAs in at least one quadrant.
NPDR is present in up to 20 percent of patients at the time of diagnosis of Type 2 diabetes, and develops in up to 90 percent of patients over the next 20 to 30 years (although estimates vary).
The severity of NPDR reflects the risk of progression to PDR over subsequent years. For example, approximately 8 percent of patients with moderate NPDR progress to PDR each year. This may increase to approximately 17 percent per year with severe NPDR; these patients may benefit from laser treatment.
Diabetes – Introduction to Retinopathy, Diabetes – Proliferative Retinopathy, Diabetes – Macular Edema.
Ocular tests, imaging investigations
Intravenous fluorescein angiography informs decision-making regarding appropriate review intervals and indications for laser treatment. It is also valuable in differentiating severe NPDR from PDR: fluorescein does not leak from IRMAs, but leaks profusely from areas of neovascularisation. Capillary nonperfusion is confirmed in areas of the retina containing cotton wool spots on clinical examination.
The physician overseeing the management of the patient’s diabetes must be notified of the presence of diabetic retinopathy, since it strongly suggests the presence of microvascular disease in other organs (particularly the kidneys). The Diabetes Control and Complications Trial (DCCT) and United Kingdom Prospective Diabetes Study (UKPDS) established the value of intensive glycaemic control in reducing the risk of onset and progression of diabetic retinopathy and other microvascular complications of diabetes. Other measures – including physical exercise, smoking cessation and management of hypertension and dyslipidaemia – may delay or prevent diabetes-related complications (such as PDR, renal failure, myocardial infarction and stroke).
Review and Laser
Review at 6 month intervals is appropriate for mild NPDR, and more frequently for moderate or severe NPDR. If diabetic retinopathy threatens to affect central vision, a decision needs to be made whether laser or other treatment is indicated.
Moderate non-proliferative diabetic retinopathy with multiple small microaneurysms, dot haemorrhages above the macula & exudates.
Moderate to severe non-proliferative diabetic retinopathy with widespread exudates, dot and blot hemorrhages and macula edema