Central  South  Dakota  Medical News
The Clinical View
by Phillip Hoffsten
23 September 2004

GLAUCOMA – THE SILENT THIEF OF VISION

     Humans have five basic senses.  Of the sense of sight, sound, smell, taste and feeling, most people treasure their sight as the most important sense.  People who have normal vision and then lose it, invariably have major problems with depression.  Thus, maintaining one’s vision is critical to well-being and mental health.  The leading cause of blindness in our society is called macular degeneration which unfortunately has no known treatment and the cause of macular degeneration is unknown.  The second leading cause of blindness is diabetic retinopathy in which high blood sugars cause degeneration of a nerve sensing cells in the eye.  Very fortunately, diabetic retinopathy can be prevented by adequate blood sugar control in the diabetic.  Once the diabetic eye disease becomes a significant clinical problem, turning the loss of vision off can be very difficult.

     The third leading cause of blindness in our society is a disease caused glaucoma which is related to the pressure within the eye.  There is a clear colorless fluid called aqueous humor that flows through the anterior chamber of the eye and maintains the pressure within the eyeball.  Unfortunately in some situations, the drainage of this fluid from the eyeball can be interrupted and cause an increase in the pressure on the inside of the eye.  When this occurs there is increased pressure on the optic nerve and it degenerates beginning on the outside of the nerve. Eventually damage will progress to the inner layers of the optic nerve causing total blindness.  The first symptom of glaucoma is the loss of peripheral vision with the sensation that one is looking through a long tube.  Other symptoms are loss of the brightness of colors and having difficulty differentiating colors and shades of light.

     The sneaky nature with which this disease can work is illustrated by a patient who came in for a check-up at his wife’s insistence.  He bragged that he had not seen a doctor for 15 years and was now 65 years of age and going on Medicare.  He had a very healthy lifestyle working on a large cattle ranch and was physically very active.  He said as far as he was concerned there was nothing wrong except that his vision seemed to be bothered slightly.  When I inquired further about this, he volunteered that colors weren’t as bright as they used to be and he had the feeling that he couldn’t see as far to the side as he used to.  The remainder of his checkup was remarkably normal but I had him see the optometrist for further evaluation of what represented glaucoma.

     Indeed, he did have a condition called open angle glaucoma and it had significantly damaged the optic nerve already.  Fortunately, he was able to start on medications that lowered the intraocular pressure and prevented further nerve damage.  He doesn’t like putting drops in his eyes each day but he especially doesn’t want to go blind, so he will do that.

He questioned why he would get glaucoma and the real answer is we don’t know.  There is an increased tendency to develop glaucoma with older age, in patients with diabetes, migraine headaches, sleep apnea, nearsightedness, and those individuals who use cortisone to treat chronic lung disease or other conditions.  The gentleman in question had none of these problems and I had to tell him that we didn’t know why he would get glaucoma.  The best way to avoid loss of vision with glaucoma is to catch it early so that the nerve damage never occurs.  The pressure within the eye goes up first and then the nerve damage occurs quietly over several years time.  Once the damage has occurred to the nerve there is no ability to regain lost function but prevention of further damage can be done.  We recommend screening any individual over age 60, those people who have chronic lung disease on cortisone and those patients that have diabetes.  These groups are especially likely to develop problems.

     The medications used to treat glaucoma include beta-blockers, the most common of which is timolol.  This is a drop that is placed in the eye twice a day.  The side effect profile is usually very low; however, this drug can cause slowing of the heart rate especially in patients that have heart disease.  It can also worsen asthma.  Another drug commonly used is called latanoprost (Zileuton, Rescula).  These drugs increase the rate at which fluid is removed from the eye.  They are given as one drop at bedtime.  The side effects with these drugs include a change in eye color.  People who have blue or green eyes will often have the eyes turn to a brown color.  This isn’t dangerous but if the drops are only used in one eye, it can result in a cosmetically unusual situation.

     Other agents commonly used include a drug used Alphagan and a product called pilocarpine.  Which medication is used is best decided by the optometrist or ophthalmologist who is prescribing the medication.  Rarely, surgery is an alternative if the drugs don’t work but surgery is rarely needed.

      These columns are written primarily as preventive medicine.  It is so much better to prevent a disease than to try and cure it or to try to stop it once the disease process is occurring.  This is most important in the case of a disease like glaucoma.  Once visual damage occurs, there is no way back.  The hope is that we can prevent further damage.  The condition is best cared for by detecting it early and preventing the nerve damage that can occur and the blindness that may follow. Since glaucoma is such a silent disease, this is one where preventive medicine is important. A visit to your eye doctor on a yearly basis is highly recommended.