What Causes Glaucoma?
Your eyes are filled with fluids. Think of a water balloon. The fluids enable our eyeballs to stay round and they do it by exerting pressure against the eyeball’s outer wall. The front of the eye, the part we can see, has a chamber behind it, and in front of the lens, where fluid circulates.
That fluid flows through some very narrow little canals collectively called the trabecular meshwork. If any of these canals become blocked, fluid drainage slows down. Meanwhile,
fluid production continues, so that pressure builds up. This is the eye’s IOP and if nothing is done to get it back down to a normal range; it will push too hard against the eyeball wall and optic nerve.
The optic nerve, where it leaves the eye near the middle of the retina, is compressed and becomes damaged. The optic nerve is made up of about 1.3 million tiny nerve fibres. They all travel across the retinal surface, and they converge next to the macula to leave the eye in a large bundle. This is our blind spot because the nerve occupies the space where light sensitive cells would have been.
Dr. Thomas Eshun-Wilson can see any glaucomatous damage as a white area where the optic nerve leaves the eye (a small area called the optic cup). Some of those fibres on the outside surface of the optic nerve bundle have been damaged so they cannot carry their visual data to the brain. That data is thus lost and we see less.
What kinds of glaucoma are there?
The most frequent kind is called Primary Open Angle Glaucoma. The angle is found in the space formed by the cornea curving up away from the flat iris. In this little space are many canals (collectively called the trabecular meshwork) that should be clear and open for fluid to drain away. When they become significantly blocked for some reason the IOP rises and the optic nerve is vulnerable to sight-threatening damage. In Open Angle Glaucoma, the angle itself is wide enough but tiny canals are blocked.
Other kinds of glaucoma are:
- Narrow Angle Glaucoma – where the angle is more acute, making it more likely that canals may be blocked. This tends to occur in longsighted people because they have relatively shallow anterior chambers.
- Acute Angle Closure Glaucoma – where the angle virtually disappears. The iris rises for some reason and pushes up against the trabecular meshwork, blocking it. This is a medical emergency. The “Acute” in its name does not refer to the angle being acute, but to the fact that it’s an acute disease, as opposed to chronic. It needs immediate attention.
- Pigmentary Glaucoma – where iris pigment flakes off into the surrounding fluid and gets stuck in the trabecular meshwork.
- Pseudoexfoliation Glaucoma – where white particles appear on the lens capsule and can get into the trabecular meshwork, blocking some of the canals.