Glaucoma - what is it?

In the "olden days", people accepted problems that occurred with old age (if you were lucky enough to live beyond seventy). "Granny was blind, but we never knew why" is a comment I used to hear frequently from older folk when asking about their family history of eye conditions. Now, we want solutions for our health problems, incluidng vision problmes and vision loss.

Granny might have been "blind" simply because she did not have the appropriate glasses, or due to a cataract (surgery for these before the early 1980's was more dramatic than it is to-day and cataracts had to be denser before the benefits of operating outweighed the risks). Or Granny could have had something more sinister - retinal detachment, retinal blood vessel haemorrhages or glaucoma. And glaucoma, if not treated early, can still cause blindness. A large part of a comprehensive eye exam in NZ and other western countries is to do with eye health and disease detection - early detection of problems means that they will be treated more easily and better.

Glaucoma can come in several forms - chronic or acute, simple or complex (self-explanatory), primary or secondary. Primary disease "just happens"; secondary happens after something else (eg glaucoma after taking a hit to the eye, maybe months or years after). Chronic disease occurs over years; acute can occur in hours. The most common type of glaucoma is chronic, simple (primary)glaucoma - so I shall discuss that here.

New research is occuring all the time, but my understanding at present (mid-2010) is that, as we age, the amount of fluid produced in the eye (to feed the back of the cornea and keep the eye' optics clear) is constant, but the drainage to remove this often becomes poorer. Sometimes this is due to an obvious blockage (secondary to...something?) and sometimes it "just happens". Our understanding is that this might be caused by microcellular changes in the tissue in the drainage system, so the cells stiffen up and do not work as well.

The upshot is that the drain works less well, and the pressure inside the eye rises. This can happen over years, and is why your optometrist monitors your eye pressures (routinely from around the age of 40; younger due to family history or from findings during the examination). The most important sign of glaucoma is a change to the appearance of the optic nerve inside the eye, which is why your optometrist will make a detailed effort to see the nerves well, and compare what is seen from one visit to the next. If these results are suspicious, a test of peripheral vision can be done, and measurements of the thickness of the nerve fibres can also be done. Changes in these readings are monitored, or the person is referred to an ophthalmologist for treatment for glaucoma, if these changes are severe enough. Any sight lost cannot be regained, because the nerve cells have died due to the pressure rise, so the aim is to detect changes before they are bad, and to prevent any more sight loss. Glaucoma that is more established is harder to treat. Some times the standard treatment of daily eye drops will not control the disease, and drainage surgery is needed in the eye. In some unfortunate people, the disease is so severe that even this will not control the disease, as the optic nerve is so damaged that any remaining cells just give up and die.

Primary simple glauocma develops over years, so it is important to have regular eye health checks (as recommended by your optometrist depending on the outcome of the exam and your family history), even if your vision is clear. If the disease is caught early enough, driving is still possible. Central vision is only affected in late-stage glaucoma, and one eye gets the disease before the second. This means that , without a regular eye health exam, you could develop glaucoma with no symptoms. And the risk increases with age, especially over 80. So make sure your older family memebers don't neglect their eyes.

So, in short, the most common type of glaucoma takes years to develop, has no symptoms, tends to occur more frequently as we age (earlier if there is a family history as there are some genes linked with some types of glaucoma) and can be treated but not cured. Catch it early, and the nastiness can be avoided. So have regular eye exams with your optometrist, even if you can see clearly.

Click on the title to go to the home page of Glaucoma NZ - you can learn more about glaucoma and sign up to receive "Eyelights", a free publication for glaucoma patients and their families.