Over the past few months my husband has gone through extensive testing. He has a dark spot in his vision, that remains constant. He has been through a CAT scan, MRI tests, field of vision tests, etc. Detached retina is ruled out, as is any sort of tumour or obstruction. Now the ophthamologist says there is such a thing as low pressure glaucoma, and that is a possibility for the diagnosis. He also says that very little is known about this condition. At the moment, he is just having my husband come in for periodic field of vision tests, and pressure tests. Can you tell me any more about this? There is no glaucoma in his family as far as we can glean.
Answered by Richard E. Gans, M. D. (xx102@ofcn.org)
To understand Low Tension Glaucoma, one must understand the concepts involved in Glaucoma in general. First, there is always a degree of pressure within the eye which is determined by a balance between fluid produced within the eye and fluid escaping from the eye. If that pressure exceeds a level where it is "tolerated" by the eye, damage to the optic nerve occurs which is characterized by typical changes in the field of vision. For most people, pressures must exceed 21 mm. Hg. for extended periods of time for this damage to occur. There are some people, however, who consistently run pressures higher than 21 mm.Hg. but do not have any optic nerve damage. They are "Glaucoma Suspect" patients in that we are concerned that they may go on to develop glaucomatous damage in the future, even though they have none now. On the other side of the coin, there are people who consistently run "normal" pressures, below 21 mm. Hg., but still have the typical type of optic nerve damage and visual field damage that glaucoma causes. These are people with Low Tension Glaucoma. For unknown reasons, their eyes cannot tolerate what would usually be considered a normal pressure.
Low Tension Glaucoma tends to be more aggressive than the typical type of glaucoma in that it effects the field of vision in areas closer to the center of vision sooner than in Primary Open Angle Glaucoma (the typical type of glaucoma). The treatment for Low Tension Glaucoma involves getting the eye pressure as low as possible, usually around 10 - 12 mm. Hg, employing either medication, laser or surgery.
In medicine, issues are not always "black and white". In the gray zone in between lies Low Tension Glaucoma in that this disease entity has some of the expected characteristic of glaucoma, but also has some of the characteristics of another disease process, anterior ischemic optic neuropathy.
Finally, although there is an increased likelihood of developing glaucoma if there is a history of the disease in the family, one does not need to have a family history of glaucoma in order to obtain the disease.
PLEASE NOTE: The information contained on this system is not intended to supplant individual professional consultation, but is offered as a community education service. Advice on individual problems should be obtained directly from a professional.
Copyright, 1994. Richard E. Gans, M.D.
Last Modified: August 23, 1996