The retina is a very unusual structure. It is the ‘film’ at the back of the eye and has a very fine blood supply across the front of it. Like all blood supplies, it has an artery and a vein component, with the artery being quite a high pressure system and the vein taking the blood back and out of the eye at lower pressure.

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The retina is a little unusual in that blockages occur in the artery and/or the vein. Blockage of the artery occurs from emboli or particulate matter coming off from the inside of the heart or heart valves, or from the inside of the blood vessels going up to the head. Vein blockages occur partly because of kinking of the vein at some point and are related to blood pressure, cholesterol and diabetes, but also to glaucoma in the eye.

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As the retina is quite like a brain, and for the most part is not able to repair itself substantially, retinal vascular disease (blockage or reduction of the blood vessels) often has a significant and maybe permanent effect on the retina’s capacity to see.

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Vein occlusions can produce some unwanted complications to the rest of the eye: the injured retina produces Vascular Endothelial Growth Factors (VEGFs) in an attempt to recreate the vessels or bypass the blockage. Overall this would seem like a useful endeavor excepting that the VEGFs spread throughout the eye and can produce new blood vessels in very unhelpful places, including the front of the eye. New vessels in the front of the eye produce a form of glaucoma (“Rubeotic”) which requires treatment for the cause (treatment of the retina) as well as the effect (the glaucoma). Rubeotic glaucoma sometimes occurs in very bad diabetic eye disease.