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  • Writer's picturePeninsula Eye Physicians

Glaucoma 101

You’ve heard the term, but what exactly does it mean?

Most people have heard the term glaucoma, but many don’t know what it means. Even people that have glaucoma often don’t have a good understanding of what it is. Let’s break down this disease into its key components.

Glaucoma is a chronic eye disease that leads to slow progressive vision loss and blindness...if untreated. High eye pressure leads to optic nerve damage, causing peripheral vision loss.

1) High eye pressure

Just like the tire in your car, the pressure in the eye needs to be at the correct level. In the eye, having pressure that is too high can cause problems.

The pressure of the eye is determined by the amount of fluid (aqueous humor) that fills the eye. This fluid is continuously produced within the eye, and continuously draining out through the outflow mechanism (trabecular meshwork) in the eye. If the fluid production is too fast, or the drainage too slow, the pressure is high.

Of note, eye pressure is NOT related to blood pressure, and this fluid is NOT related to tear fluid.

We refer to the eye pressure as intraocular pressure, or IOP, and this is measured during your eye exam. Average IOP is 10-21. Glaucoma typically occurs in eyes that have an IOP higher than 21. However, glaucoma can even occur in eyes that have a normal IOP. In these eyes, the optic nerve may be “extra-sensitive” and sustains damage even with normal eye pressure.

Eye pressure is the culprit for damage in glaucoma - and therefore, all proven treatments for glaucoma (including eye drops, laser, and surgery) work by reducing eye pressure.

2) Optic nerve damage

When the pressure is high in the eye, the optic nerve feels the impact. Nerve tissue can only thrive in optimal environments. In a high pressure setting, the optic nerve starts to die.

The optic nerve is in the back of each eye, and transmits visual input from the eye to the brain. The optic nerve is comprised of over one million nerve fibers. In glaucoma, there is slow damage and atrophy of these nerve fibers over time.

When your eye doctor examines the inside of your eye, usually with dilation, the head of the optic nerve can be visualized. If the nerve looks thin on exam, an optic nerve photo scan is often done to quantify the thickness of the nerve. This scan helps determine if the nerve is truly thin, and also helps to follow progression.

Because nerve tissue cannot be regenerated, any damage is irreversible. This makes early detection and treatment essential in glaucoma, to prevent further damage to the optic nerve.

3) Peripheral vision loss

Imagine seeing only the central portion of what most people see. Along with loss of nerve tissue comes loss of vision. As the nerve thins out, your area of vision shrinks.

The nature of vision loss caused by glaucoma has earned it the nickname “the silent thief of sight.” The blind spots are peripheral at first, and slowly progressive. Because of this, it is possible to lose up to 50% of your vision before you even notice it! During your eye exam, when glaucoma is suspected, an intricate peripheral vision test is performed. We want to detect glaucoma before you develop any blind spots.

All this talk of irreversible nerve damage and permanent vision loss may sound scary.

But here’s the good news...

1) Glaucoma is easy to detect with eye exams.

2) And if detected, it is very treatable.

So if it’s been a while since you’ve had an eye exam, make sure to have your eyes examined.

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