New Angle on Glaucoma Causes

There are several types of glaucoma and the most common one is open-angle glaucoma. Glaucoma is detectable damage to the optic nerve caused by high intraocular pressure and its causes are not well understood. The fluid inside the eye always exerts a certain amount of pressure outwards, and in a normal eye, the cornea (front clear part) holds its curvature steady, the lens, iris, and sclera are not damaged by the pressure, and the optic nerve and retina remain healthy.

However, in a glaucomatous eye, the pressure is too high and causes eye tissue damage. When the optic nerve is damaged, our sight is compromised. Glaucoma is a progressive disease, and if not treated will cause blindness.

The retina is made up largely of light-sensitive cells which receive the image information in light rays entering the eyes. They convert it to electrical energy. The optic nerve is connected to the retina and carries this electrical (neural) energy to the brain, which interprets it. When the optic nerve is damaged, it is less able to carry that vision information to the brain, which gradually reduces our visual field until it becomes zero.

Diagnostic Tests

Traditionally, glaucoma is diagnosed through several tests. Two are tests of intraocular pressure:

• The 'puff test' -- where a puff of air is sent to the eye and gives a measurement of how much intraoculat pressure that eye has
• The visual field test -- where tiny lights flashing for a moment are the stimulus for you to press a button at each light. The testing system converts this into a map of each eye, with black areas where lights flashed but you didn't press the button because you didn't see them.

A third is an examination of the optic nerve:

• Stereoscopic photographs are taken of the optic nerve

Newer tests attempt to measure the thickness of nerve fibers in the retina. Glaucoma reduces their thickness until they are lost. By measuring any changes in the thickness of these fibers, these tests detect the glaucoma progression.

A Recent Mayo Clinic Study

Using Mayo Clinic records, a team of ophthalmologists (all members of the American Academy of Ophthalmology) and others recently compared intraocular fluid pressures to cerebrospinal fluid (CSF) pressures. CSF surrounds the spinal cord and brain, extending to the area of the optic nerve.

They chose 28 glaucoma patients and 49 control group patients without glaucoma. Both groups had received eye examinations, and had had CSF samples taken through a lumbar puncture between 1996 and 2007.

The researchers found that CSF pressures were significantly lower in all glaucoma patients than they were in any of the control group patients. This was independent of any patient's age, or the reason he or she had had the lumbar puncture done.

In other words, they found that in the glaucoma patients, lower CSF pressures were combined with higher intraocular pressures. Further studies are now planned, to learn more about the role of CSF pressure in the development of glaucoma.

If you are approaching age 40 or so, and have not had any glaucoma testing, it is strongly urged that you do so. Glaucoma can creep up silently on a person, and you may not notice anything is amiss until you have permanently lost a significant amount of vision. If you are in the Bloomington or Peoria areas in Illinois, please visit the Gailey Eye clinic, where any of six highly-trained ophthalmologists can help you keep your eyesight intact.