Question 7: What are the three most common causes of neovascular glaucoma?
Question 7: What are the three most common causes of neovascular glaucoma?
Answer:
Neovascular glaucoma (NVG) is a secondary glaucoma in which new vessels, and subsequently fibrous tissue, form in the anterior chamber angle of the eye. This leads to blockage of the angle, which inhibits aqueous drainage, causing elevated intraocular pressure (IOP).
The most common causes of neovascular glaucoma are:
- Diabetic retinopathy
This is most commonly related to proliferative diabetic retinopathy (PDR), approximately 50% of patients with PDR have rubeosis iridis (Shazly et al 2009)
- Ischemic central retinal vein occlusion
The definition of an ischemic versus and non-ischemic CRVO can be made based on a combination of factors such as VA, visual fields and electrodiagnostic testing, fluorescein angiography and fundus findings. (Hayreh 2007)
The incidence of neovascular glaucoma after CRVO is approximately 16%. If VA is less than 6/60 within 1 month of a CRVO the chance of NVG is over 30%, in those with VA better than 6/12 it is only 5% (Shazly et al 2009)
Classically neovascular glaucoma is known as the ‘100 day glaucoma’ is it usually occurs 3 months after the CRVO. 80% of cases occur within 6 months (Shazly et al 2009)
- Ocular ischemic syndrome (OIS)
This is due to insufficient blood supply to the eye, most commonly due to occlusive disease at the carotid artery however this can also be due to occlusion at the aortic arch, ophthalmic artery and ciliary artery.
Patients with OIS can present with a normal or even low IOP despite angle neovascularisation, due to ischemia of the ciliary body and decreased aqueous production
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