When teaching our UCLA ophthalmology residents at our large county hospital, Olive View UCLA Medical Center, we encounter many patients with untreated vascular disease which has resulted in severe ocular sequelae. Neo-vascular glaucoma, like the name implies, results from growth of new blood vessels in the anterior segment which can be seen on the iris and also in the angle. These cause outflow blockage and this results in a very high intra-ocular pressure, often 50 to 60 mmHg or even more.
Diabetes is the primary cause in our clinic with patients having extensive proliferative diabetic retinopathy, but this can also be from hypertensive related conditions such as central retinal vein occlusion (CRVO). Neo-vascular glaucoma is sometimes referred to as “90-day glaucoma” since the timing of the IOP rise is usually about 3 months after the CRVO.
Looking at the cornea gives us important information. If the cornea is cloudy and edematous, then it is more of an acute condition, whereas a totally clear cornea means that the IOP has likely been elevated for at least a month or two and now the corneal endothelial cells have adapted and are now keeping the cornea clear.
These patients can do well with placement of a seton drainage tube to alleviate the high intra-ocular pressures. But remember that there is an underlying problem that is causing this neo-vascular glaucoma. These patients also will need anti-VEGF injections like Avastin (off-label in the USA) and pan-retinal photocoagulation (PRP laser).
In patients with cataracts as well, we will sometimes do everything at once: remove the cataract, perform PRP with the indirect ophthalmoscope laser, and implant the Ahmed valve FP7. We can use the IOL calculations from the fellow eye for most patients if there are issues with biometry of the affected eye. Adding 0.5 to 1.0 diopters to the IOL power can help ensure a more useful refractive outcome.
Another critical take-home message: the patient has two eyes and while the sick eye with neo-vascular glaucoma is important, the other eye is arguably even more important. The disease process that is damaging the eye with neo-vascular glaucoma may very well affect and damage the other eye in the near future. Always examine and fully treat both eyes! The other eye may have earlier changes such as neo-vascularization of the iris without neo-vascularization of the angle, thereby still maintaining a normal intra-ocular pressure. But that can change in a matter of weeks.
The technique for surgery is shown in the video below with specific recommendations for suture choices and surgical pearls. To verify outflow through the tube, I teach residents to instill a small aliquot of triamcinolone particles in the anterior chamber and then to increase the IOP by injecting BSS via the paracentesis. Once the pressure rises (usually above 15 mmHg), the steroid particles will flow right through the tube. To prevent hypotony in the immediate post-op period, the anterior chamber is given a 75% fill of dispersive viscoelastic. This will slowly work its way out of the anterior chamber as the eye heals and any increase in IOP will allow flow through the seton tube.
Click below to learn the technique of Ahmed Valve FP7 surgery that I teach to my residents: