nonproliferative diabetic retinopathy
Last edited 05/2023
This describes increasing ischaemia superimposed on background diabetic retinopathy.
Diabetic retinopathy in its earliest stages is also called nonproliferative diabetic retinopathy.
The most conspicuous feature are cotton wool spots - "soft" exudates representing microinfarcts in the nerve fibre layer.
Non proliferative diabetic retinopathy (NPDR) is the earliest stage in disease progression (1).
- In the international (AAO) classification, NPDR is graded as:
- mild
- moderate
- severe.
- In the National Screening Committee (NSC)-UK classification, NPDR is graded as:
- background (Level R1)
- pre-proliferative (Level R2).
The nonproliferative stages of diabetic retinopathy are characterized by
- microaneurysms
- the first clinical signs of diabetic retinopathy caused by isolated capillary occlusion with adjacent non-occluded capillaries forming saccular or fusiform swellings.
- these appear as isolated, spherical, red dots of varying size
- individual microaneurysms may leak resulting in dot haemorrhage, oedema and exudate
- dot haemorrhages cannot always be differentiated from microaneurysms as they are similar in appearance but with varying size
- retinal thickening (oedema) and lipid deposits (hard exudates)
- caused by increased retinal vascular permeability
- may occur during these or later stages of retinopathy
- as DR progresses, progressive capillary occlusion leads to the development of
- blot haemorrhages
- where clusters of capillaries occlude, intraretinal blot haemorrhages develop
- such haemorrhages may occur throughout the full thickness of the retina
- they are considered to represent a deep retinal infarct
- intraretinal microvascular anomalies
- dilated pre-existing capillaries
- venous changes
- venous beading - occurs when veins run through areas of extensive capillary closure
- venous loop - are infrequent and though to develop due to small vessel occlusion and opening of alternative circulation
- venous reduplication - is rare and usually occurs in conjunction with venous beading
- cotton wool spots
- are believed to represent the swollen ends of interrupted axons where build-up of axoplasmic flow occurs at the edge of the infarct (1,2).
The rate of progression to proliferative diabetic retinopathy after 10 years is 6.6% (3).
In those with preproliferatic retinopathy at baseline, the cumulative incidence of sight-threatening maculopathy or retinopathy after 6 years was 70% (4).
Reference:
- The Royal College of Ophthalmologists (RCOphth) 2012. Diabetic retinopathy guidelines
- American Academy of Ophthalmology (AAO) 2019. Preferred Practice Pattern guidelines. Diabetic retinopathy.
- Ockrim Z, Yorston D. Managing diabetic retinopathy. BMJ. 2010;341:c5400.
- Younis N, Broadbent DM, Vora JP, Harding SP.; Liverpool Diabetic Eye Study Incidence of sight-threatening retinopathy in patients with type 2 diabetes in the Liverpool Diabetic Eye Study: a cohort study. Lancet 2003;361:195-200
pathogenesis of diabetic retinopathy