The Silent Killer of Eyes

Does everyone know about the Silent Killer? High Blood Pressure? How high blood pressure can exist silently – without symptoms – for years until the sudden heart attack or stroke happens? There is also a silent killer of eyes – glaucoma.

Three million Americans have glaucoma – about 1 in a 100. Only half of them know they have it. And if human nature holds true, only half of them are doing something about it. That’s one in four. That means three out of four are facing limited or total loss of vision. Glaucoma is the silent killer of eyes.

The human eye is a membranous bag that maintains it shape by constantly pumping a small amount of fluid into the eye and constantly draining the excess fluid out of the eye. The drainage area for the eye is located in front of the outside edge of the iris, the colored circle of the eye. The flow of fluid is regulated to keep the internal pressure in the eye at 11 to 20 mm Hg (millimeters of mercury). Every person has a different normal pressure, but the pressure is usually within that range.

If the fluid is produced too fast (unusual)or if the fluid doesn’t drain rapidly enough (usual), the pressure inside the eye increases to a point significantly higher than what is normal for that individual – from 11 to 17 mmHg or from 15 to 23 mm Hg. The higher pressure doesn’t have to be outside the range of normal, it just has to be higher than is normal for that individual.

The increased pressure in the eye pushes equally on all the surfaces inside the eye. The most sensitive site is the optic nerve – the round disc in the back of the eye where the million or more nerves for seeing exit the eye, carrying messages of observed light from the retina (the back inside surface of the eye) to the brain for interpretation as sight. As the pressure increases, the optic disc begins to “cup”, that is, indent into the optic nerve. The increased pressure decreases the fluid flow through these nerves and decreases the blood flow to these nerves. They begin to die.

This is a painless process. The only evidence that this is happening is the observation that the optic disc looks cupped and that there is loss of vision at the edges of the visual field. At first the loss of vision is not noticeable. But gradually one becomes aware that there are certain areas of the visual field – especially in the periphery – where objects seem to be cloudy or disappear altogether, then show up again as the gaze moves away from them. These blank spots are where the nerves have already died. They cannot be replaced. The good news is that the process can be stopped with proper treatment, usually drops but occasionally surgery.

Yes, there is a rapidly developing form of glaucoma – acute narrow angle glaucoma – that develops over hours to days. It is not silent. It causes a red, painful, swollen, cloudy eye and may lead to nausea and vomiting – a true medical emergency. This is caused by medicines, drugs, the dark, excitement – anything that causes the iris opening to dilate, narrowing the angle between the back of the cornea and the front of the iris, blocking the drainage of fluid from the eye. The treatment is making the iris opening smaller.

But chronic glaucoma is secretive, sneaky, and an eye killer. Those people who are near or far-sighted, those with diabetes, those taking steroids, and those of African or Hispanic descent are all more susceptible. But everyone over 40 needs to have a baseline eye exam – to find out what their personal normal eye pressure is. Everyone over 65 needs an eye exam every one to two years to see if their pressure is increasing.

Don’t wait until the vision begins to fade and to narrow. This is the silent killer of eyes. This is the ounce of prevention. Have the eyes checked. Glaucoma cannot be detected unless someone checks. Make sure it is you.