Diabetic Retinopathy

Diabetic Retinopathy is one of the commonest cause of blindness in the world. Diabetics are at 25% more risk to be blind than normal people. Also, almost half of the diabetics at some stage develop eye disease. Hence, diabetes is a major predisposing factors to ophthalmic pathology.


Ocular diseases that are associated with Diabetes include:

a- Diabetic Retinopathy
b- Cataract
c- Glaucoma
d- Infections

(Delayed healing is also a result of diabetes)


Pathogenesis:

The major factor in the pathogenesis of Retinopathy in diabetics is a microangiopathy of vessels supplying the retina )or a part of it(.

The main vascular damage can be divided into two parts: a) Leakage; b) occlusion

a) Endothelial cells rely exclusively on glucose for nutrition and insulin helps in the transport of glucose into them. Thus, when there is absence of insulin or a resistance to it, the cells start becoming undernourished. And overtime they suffer injury (and most likely cell death). The dead cells result in a leaky and weakened vessel wall. The leaky vessel wall leads to edema of the retina, followed by hemorrhage and finally WBC infiltration - thus resulting in damage to the retina.

b) As the vessel continues to weaken, microaneurysms form in the vasculature which over time can get occluded and thus lead to infarction of the retina supplied distally to the occlusion.
As the retina is denourished due to thrombosis of the vessel supplying it, there is release of Vascular Angiogenesis Factor (VAF). Under the influence of VAF, new blood vessels are formed to keep the retina nourished but that is to no avail as the new vessels leaky and weak and thus more hemorrhage and edema occurs, resulting in further loss of vision.


Risk Factors:

a) Duration of diabetes
b) Control of Diabetes
c) Pregnancy and other diabetogenic conditions
d) Anemia
e) Hypertension - DM and HTN go hand in hand
f) Smoking
g) Obesity and Hyperlipidemia


Symptoms:

This form of retinopathy is asymptomatic initially. Although some people might complain of dark areas in their vision.


Signs:

On Ophthalmic examination, red (hemorrhagic) and white (exudative) dots are seen. Exudates are of two types: hard and soft. Hard exudates contain protein, have marked edges and are small and discrete. the soft exudates on the other hand are of a lighter colour. They appear softer and have less marked edges with fuzzy borders.


Classification:

Diabetic Retinopathy are classified in two types depending on vascular proliferation. They are as follows:

a) Non-proliferative: they don't grow from the initial lesion and there is no neovascularization, or only minimal.

b) Proliferative: there is dangerous level of neovascularization and they appear as fronds. These vessels might bleed into the Vitreous and give rise to opaque membranous plaques which can then result in retinal detachment.
If all the above is present along with glaucoma, the condition is called Advanced Diabetic Eye DIsease (ADED).


Diagnosis:

It is based on positive history of Diabetes and Ophthalmoscopic examination.


Complications:

a) Vitreous hemorrhage
b) Retinal detachment
c) Formation of opaque membranes
d) Burnt-out stage


Treatment:

Specific: is to get rid of the new vessels being formed and removing the occlusion
Non-specific: control Diabetes and Hypertension; avoid ischemia


Screening:

Screening is an important tool in preventing the development of Retinopathy in cases with high index of suspicion. Diabetics should be examined at least once a year and the frequency should increase with every decade.