September is Save Our Sight Month, an initiative from the New Zealand Association of Optometrists to promote the importance of regular eye examinations. One of the most important conditions optometrists are looking for during a routine examination is glaucoma.
Often called the "sneak thief of sight", because it causes vision loss without symptoms in its early stages, glaucoma is actually a group of conditions that cause vision loss due to excessive pressure within the eyeball (intra-ocular pressure, or IOP). Glaucoma affects about 1/200 people under the age of 50, but increases to 1/10 people over 70 years old. Risk is increased by having a positive family history of glaucoma, particularly a brother or sister with the disease. It is the leading cause of preventable blindness in NZ and other developed countries.
Although the exact process by which glaucoma damages the eye is still being researched, what we know is that excessive pressure within the eyeball affects the blood supply to the fibres of the optic nerve. This causes gradual loss of the nerve fibres which carry information from the eye through to the brain. As these nerve fibres are lost, "blind spots" form in the areas served by those nerve fibres. These are initially in the mid-peripheral vision, but enlarge as the disease progresses. Initially the sufferer is not aware of this loss of peripheral vision, as the visual system fills in the missing areas. There are no areas of blackness to alert the sufferer that their side vision is deteriorating. In fact, quite a lot of vision can be lost before some one with glaucoma notices they have a problem. Ultimately, if left untreated, the increasing loss of visual field can lead to total blindness.
By far the best and easiest way to make sure you don't get caught out by this insidious disease is to get your eyes regularly examined by an optometrist. The New Zealand Association of Optometrists recommends a checkup every 2 years for people aged 40 and older. An optometrist will measure the IOP, and examine the optic nerve for signs of glaucoma, as well as other eye disease conditions. At Cassidy Eyecare, we routinely take digital images of the back of the eye, which is helpful in detecting changes in the optic nerve appearance over time - this is often the best way to diagnose this often-tricky condition. We also have computerised visual field analysers to accurately measure the zones of peripheral vision which are affected by glaucoma, again allowing us to detect signs of this disease in the early stages.
For more comprehensive information and support, see the website of Glaucoma NZ.