Pathogenesis of Retinopathies... In a bid to understanding the challenges it poses to the primary eye care Optometrist in the Nigerian setting!

Optom
Retinopathy is a retinal disease that targets blood vessels in the retinal vasculature! Weakening of blood vessels is the focus of the disease while disruptions of vascular blood supply (ischaemia), leaking of tiny blood vessels (aneurysms), leaking of blood nutrients like lipids into the transparent retina (hard exudate/edematous macular), ischaemia-induced retinal nerve-ending apoptosis (soft exudate), blockage of blood vessels (thrombosis), formation of new blood vasculatures in non-vascular routes (neovascularization) like rubeosis iridis, rupture of neovascularized vessels due to mechanical pressure (retinal/sub-retinal/vitreous hemorrhages) are some of the common signs of most retinopathies.
 It should not be disputed, this eye disease can easily cause irreversible or absolute blindness. Hence it is very important to know about this condition as early as an Optometrist can and be able to make a blindness' saving decision while not leaving any stone unturned.
Retinopathy can be proliferative or non-proliferative.  A retinopathy is proliferative if blood vessel rupture is accompanied by neovascularization of blood vessels along the surface of the retina. A non-proliferate retinopathy is a type of retinopathy without rupture of blood vessels and without neovascularization of the retina.  
 Different systemic diseases like Diabetes, Hypertension, Sickle cell, etc,  causes retinopathy; or it can be caused by pre-term delivery (Retinopathy of Prematurity), and due to idiopathic consequences (central serous retinopathy). Occlusions of any part of the central retinal arteries or veins can lead to retinopathy. By far, the most important Retinopathies are those caused by Diabetes or Hypertension, because of the classical picture they often leave behind in the acute phase of this disease and because they commonly affect alot of people all over the world.
Diabetes is a systemic disease characterised by chronic hyperglycemia. Diabetes retinopathy is a result of micro-vascular endothelial defect commonly referred as micro-angiopathy. Hyperglycemia promotes artherothrombosis process by making blood to form clots, to adhere to the endothelial plagues which results from age, nutrition and genetics. The formation of thrombus in the small retinal vessels and else where triggers aneurysms, occlusions of the retinal Vein or Artery, formation of neovascularization, formation of Vascular Endothelial Growth Factor (VEGF) in neovascularization and other inflammatory processes, subsequent degeneration of the retinal-blood barrier paints a picture of the classical signs of Diabetic retinopathy.
Hypertension breaks down vascular homeostasis by the increased wear and tear associated with elevated blood pressure for a prolonged period of time. Hypertension is a result of hardened (slerosing) blood vessels due to age (involutional sclerosis) or some other risk factors like smoking on the normal cardiovascular activity. The effect of the increasing 'pump' rate on the vessels to compensate for arterial resistance and the subsequent vaso-constriction of capillaries and other small vessels in the retina leads to increased vascular permeability and associated related retinopathy due to Hypertension. This high blood pressure also causes arteriolosclerosis (secondary to injury of on the endothelial surface of retinal arterioles) which is very important in formation of hypertensive retinopathy.
The pathogenesis of Retinopathy of Prematurity highlights the importance of Oxygen to the Retina. The Retina of the pre-term baby is characterised by under-developed retinal vessels. Due to oxygen treatment a poorly understood process leads to neovacularizations. The neovascularization seems to be a biological compensatory process that has gone viral. VEGF is a major factor in this disease process.
 Sickle-cell retinopathy has its pathogenesis in the associated retinal hypoxia resulting from haemoglobinopathy, a feature of sickle-cell anaemia.
To be continued...
Thanks,
Dr Ezebuiroh Victor Okwudiri.