Secondary glaucoma

Throughout this guide, we have mostly talked about the primary glaucomas, those that happen largely because of inherited traits and things we don’t fully understand. By and large, in primary glaucoma there is really nothing else wrong in the eye (or the body) other than glaucoma itself.

Secondary glaucoma happens because of something else. It can be a something in the eye or in the body that affects the eye. If we total up all those with glaucoma in the world, the secondary ones are still a fair number, maybe 10% of all glaucoma. They much more often affect one eye and not both eyes, unlike primary open angle or angle closure that affect both eyes. All secondary glaucomas share the feature that the eye pressure is above normal due to something that causes abnormal outflow of aqueous.

Some people think we should classify some of the more common subgroups of open angle glaucoma as separate and secondary. This includes pigment dispersion syndrome and exfoliation syndrome (see section How did you get glaucoma?). In this guide, we considered these as primary.

Probably, the most common secondary glaucoma in the developed world are those that come from having new blood vessels grow in the meshwork and block outflow of aqueous: the neovascular glaucomas. We now know that this usually happens when the retina does not have enough blood supply. This leads to production of a chemical called vascular endothelial growth factor (VEGF) that floats around the inside of the eye, allowing new vessels to get blood flowing. The problem is that the new vessels grow in the wrong places, messing up vision, detaching the retina, and causing glaucoma. People with diabetes sometimes have this happen; as well as people who have a blockage in a main artery or vein in the eye (central retinal artery or vein occlusion). It also happens when the main neck artery to the brain blocks off (carotid artery occlusion). Nothing works to win against neovascular glaucoma unless we improve blood flow (open the carotid artery), decrease the need for blood in the retina (by lasering the retina), or inhibit VEGF (with injections of special blockers into the eye: Lucentis and Avastin). Once these things are done, we can treat this form of glaucoma with eye drops or with surgery and limit the damage.

Injuries to the eye are a frequent cause of both short-term glaucoma, due to ill effects of the injury, and long-term effects of damage to the meshwork by the blow. Frequent things that do this are bungee cord whip-backs into the eye, champagne corks for unwary celebrants, smaller athletic ball hits (squash, handball, lacrosse) for those who don’t wear eye protection, and pellet and BB guns. All cause rips in the meshwork that scar it shut and make the pressure higher. Other associated injuries to the eye complicate the overall picture. Surgery is often needed to stop damage. Wearing safety glasses whenever you are involved in activities that can lead to eye injuries is a smart and safe way to avoid this.

Those with inflammation in the eye (uveitis) develop high eye pressure when inflammation or the treatments for inflammation (steroids) raise eye pressure. To make things more complex, inflammation sometimes also lowers eye pressure, so it can flip from high to low in an unpredictable way. Many inflammatory diseases can lead to glaucoma, including juvenile rheumatoid arthritis, sarcoidosis and other similar disorders. Medical and surgical glaucoma treatments are used, but are often more difficult to implement.

The list of secondary glaucomas is very long. One that has been of great interest to our group is the iridocorneal endothelial syndrome (ICE syndrome). Partly, it’s a favorite because we gave it its name, and we have seen many persons with it over the years, even though it is not that common. It happens only in one eye, it looks somewhat like angle closure, and pressure can go quite high early in life, even in the 20s and 30s. The chief defect is an overgrowth of the cells on the back of the cornea (corneal endothelium) that blocks up outflow of aqueous. We treat with eye drops and often with surgery, sometimes having to replace the cornea with a transplant from an eye bank donor.