A 70-year-old man with right central retinal vein occlusion 3 months ago presents with a painful red eye, a visual acuity of hand movements and a right relative afferent pupillary defect (RAPD). An ophthalmologist examined him when he first lost vision in his right eye but he has not been to any further appointments. What is going on here?

This does sound very much like rubeotic glaucoma. It has all the ingredients: central retinal vein occlusion, RAPD, a painful red eye and the passage of 3 months since the occlusion. Let us break this down into smaller parts.

Older people sometimes have a central retinal vein occlusion due to atherosclerosis in a nearby artery. Atherosclerotic plaques cause hardening of arteries and hardened arteries can press onto nearby veins. When this happens to the central retinal vein, blood cannot get out of the eye. If deoxygenated blood cannot get out of the eye, fresh oxygenated blood cannot get in and a situation of oxygen starvation (ischaemia) is set up. Retinal tissue is not prepared to tolerate ischaemia so new blood vessels are created following the release of a chemical called VEGF (vascular endothelial growth factor-a protein produced by cells that stimulate the formation of blood vessels). These new (neo) blood vessels have weak walls and grow in the wrong places like the surface of the retina or on the iris.

The RAPD in the affected eye confirms the presence of an ischaemic central retinal vein occlusion and not non-ischaemic central retinal vein occlusion, which is a much less serious eye condition and in which an RAPD is much less likely to be noticeable in the clinical environment.

It is interesting that new blood vessels growing gradually in the anterior chamber can cause high intraocular pressures but as this occurs slowly over around 3 months the slow steady rise in intraocular pressure does not cause a red painful eye even though the pressure can be 60 to 70 mmHg.

Fragile new blood vessels in the anterior chamber are likely to lead to blood and where there is blood there is often scar tissue formation. Scar tissue shrinks and if located in the anterior chamber it closes the angle between the iris and the cornea and prevents aqueous from leaving the eye. This leads to a rapid increase in intraocular pressure and this is what causes the unilateral painful red eye.

It takes around 100 days from the time of the central retinal vein occlusion to the anterior chamber angle closure. During this period ischaemia develops, VEGF is released, anterior chamber blood vessels develop and rupture, blood flows, scar tissue forms and shrinks. Hence, the other name of is condition; 100-day glaucoma.

Of course, the patient needs emergency attention from an ophthalmologist specialising in the treatment of retinal ischaemia.

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