Glaucoma is a complex multi-factorial disease. In plain English, that means it is not one disease and not caused by one factor only. Recent knowledge has made us acutely aware that eye pressure is not the determining factor in the diagnosis of glaucoma. When the pressure inside the eye was above 21 in the past glaucoma was thought to be present. Today we know that some individuals will never develop glaucoma even though their eye pressure readings may stay in the 30’s while other patients cannot tolerate normal pressures without sustaining sight loss. Glaucoma is more of a vascular disease of the optic nerve of the eye. When the auto-regulation of the blood supply starts to fail, vision begins degrading. High eye pressures do cause compression of the blood vessels supplying the nerve, but healthy blood vessels with good autoregulatory mechanisms can sustain very high pressures. Eye pressure is not static and can vary throughout the day. When we read it once when we are at the optometrists office it is only a thin slice of what your pressure range could be over a 24 hour period.
The Human Genome Project mapped the human gene structure and was an enormous undertaking completed in 2003 taking 13 years and sequencing over 3 billion codes of base pair information. This has opened the doors to tremendous future strides in treating all diseases. There is a chromosome with a gene that codes for the production of a protein called myocilin-a protein that makes up part of the structure of the trabecular meshwork. This meshwork is responsible for keeping the fluid balance in check by allowing continual drainage. When something goes awry with the drainage the pressure goes up increasing your risk for developing glaucoma. Ocugene is a company that has developed a test for defects in the myocilin/TIGR gene(GLC1A). Unfortunately, this gene is only responsible for about 4% of the cases of glaucoma. It can be useful when there is a suspected family history since patients with this genetic marker tend to have rapidly developing glaucoma and should be treated more aggressively. It also tends to be more commonly associated with glaucoma under the age of 40.The WDR36 (GLC1G) gene has also had mutations that appear to be associated with glaucoma. The optieurin gene(GLC1E) has reportedly been associated with an increased incidence of glaucoma in patients with normal pressures. One uncommon form of glaucoma know as exfoliation has also has seen the development of a genetic marker test, but due to the rarity of this condition it is not widely used .
All together, probably less than 10% of glaucoma has a direct genetic cause, and due to the expense of genetic testing it is rarely utilized. The complexity of testing is compounded by the fact that numerous defects at each gene can ocurr, and sometimes it may take two or more genes with flaws to create glaucoma. Even the most accepted genetic factor, the myocilin gene, may cause glaucoma from defects in areas other than the trabecular meshwork. It is very early in the age of genomics. Perhaps the greatest benefits will not be in diagnosing glaucoma but in tailoring treatment and actually curing some forms of glaucoma in the future.
General health issues are the most important risk factors, and some you can control. Smoking and cardiovascular diseases are high risk factors for developing glaucoma. Make sure you stay fit and have well controlled blood pressure. Keep preventative appointment and regular eye exams to monitor the eye pressure. Age is a risk factor but consider it a good one. A longer life is usually better all things considered! Most vision insurance plans like Vision Service Plan, Medicare, and many others cover preventative annual eye examinations.