Diabetic Retinopathy

Introduction

Diabetes is the leading cause of blindness between the ages of 20 and 74 years.
Individuals with DM are 25 times more likely to become legally blind than individuals without DM. Blindness is primarily the result of progressive diabetic retinopathy and clinically significant macular edema.

Pathogenesis

Diabetic retinopathy is a microvascular disease that leads to capillary occlusion. It affects the retinal precapillary, arterioles, capillaries and venules. Early pathological features include thickening of the basement membrane, loss of pericytes and the development of microaneurysms. Persistent hyperglycemia is considered to be the primary cause of changes in the vascular endothelium. The end result is an ischaemic retina, which releases cytokines that promote the growth of new blood vessels, particularly vascular endothelial growth factor, which is also involved in the early stages of increased vascular permeability.

Risk factors

1. Duration of diabetes
2. Poor control
3. Pregnancy
4. Hypertension
5. Hyperlipidaemia
6. Nephropathy
7. Cataract surgery

Classification

Diabetic retinopathy is classified into two stages:
1. Nonproliferative
2. Proliferative.



1. Nonproliferative diabetic retinopathy


This usually appears late in the first decade or early in the second decade of the disease and is marked by retinal vascular microaneurysms, blot hemorrhages, and cotton wool spots. Mild nonproliferative retinopathy progresses to more extensive disease, characterized by changes in venous vessel caliber, intraretinal microvascular abnormalities, and more numerous microaneurysms and hemorrhages.

2. proliferative diabetic retinopathy


The appearance of neovascularization in response to retinal hypoxia is the hallmark of proliferative diabetic retinopathy. These newly formed vessels appear near the optic nerve and/or macula and rupture easily, leading to vitreous hemorrhage, fibrosis, and ultimately retinal detachment.






Management

1. Control of risk factors delays the onset of retinopathy and can slow progression of the disease
2. Laser treatment is the only known means of stopping the progression of diabetic eye disease.


Screening

It is important to screen all patients with diabetes for eye disease. It can prevent blindness and has been shown to be cost-effective. The GP, the optometrist or the diabetologist may undertake this, depending on local policy.