TAKE HOME POINTS:
- Glaucoma is a leading cause of blindness.
- Glaucoma’s first and only symptom can be loss of vision.
- Glaucoma is a disease of the optic nerve and brain.
- Many risk factors can lead to the development of glaucoma.
- Increased pressure in the eye is a leading cause of optic nerve damage.
- Glaucoma is not a “number”, i.e., the eye’s pressure reading.
- The goal of treatment is to arrest or prevent optic damage.
- Early detection and treatment can prevent damage or its progression.
Your optic nerve carries nerve impulses for vision from the retina of the eye to the brain where the transformation into the miracle called vision occurs. When the optic nerve is damaged, vision is lost. Although exciting research promises new
hope, there are presently no techniques to repair the nerve. The most common cause of damage to the optic nerve is glaucoma, one of the leading causes of blindness in worldwide.
I recently attended the Midwest Glaucoma Symposium at the University of Pittsburgh. This two-day meeting brought together eminent glaucoma researchers and clinicians from the US and Canada. Some of them – Drs. Joel Shuman of Pittsburgh, Paul Lee at the University of Michigan and Rob Weinreb at UC San Diego – are friends of mine. They are brilliant scientists.
No one knows what causes glaucoma. It occurs more commonly as we age. Family history can play a role but there is no direct genetic link. High blood pressure, hardening of the arteries, smoking, even sleep apnea play a long-term role in its development. African-American, nearsighted and patients with diabetes must be especially cautious.
Although it can’t be cured, glaucoma can be successfully treated. The goal of treatment is preservation of the structure and function of the optic nerve. This is counter-intuitive to some patients’ – and doctors’ – perception of glaucoma; they think of glaucoma as a number. The eye, like a soccer ball, has an internal pressure. This pressure is measured during an eye examination and is reported in millimeters of mercury just as a barometer’s reading. The average pressure within the eye is approximately 16. Pressures above 21 are judged above normal. But, at least 30% of patients with the disease may have “normal” pressures below 21. The eye’s pressure is the only risk factor that can be treated.
New studies show that eye pressure varies widely during the course of the day. The pressure that is determined at the time of an appointment can be lower or higher and, sometimes, much lower or higher than it is, say, in the middle of the night. In most people, the highest pressure in the eyes occurs in the wee hours of the morning. This may be due to positioning, lying down rather than standing. It might be due to the changes in the body that occur during sleep that affect blood flow and production of fluid in the eye. It is an important consideration. In the future, around the clock monitoring of the eyes’ pressure may be feasible. Dr. Weinreb has reported his clinic’s experience with a contact lens device.
The eye is a highly regulated plumbing system. Essential nutrients exist in fluid produced by the ciliary body, a small tissue that lies behind the pupil and the colored iris. The fluid percolates around the pupil into the small space just behind the eye’s window, the cornea. Some of this fluid – called aqueous – then drains from the eye through a grate-like structure called the trabecular meshwork; as much as 50% of the fluid can also flow out of the eye through other channels.
If the balance of inflow and outflow of fluid is upset, the pressure in the eye increases. In some patients, elevated pressure in the eye can cause tiny nerve fibers that make up the optic nerve trunk cable to die. Each normal eye has about one-and-a-quarter million such nerve fibers. The effect of cell death causes profound changes in the sight centers in the brain. Vision is lost and eventually blindness may ensue. The goal is to protect the optic nerve by changing those things we can change, especially the increased pressure in the eye and certain behaviors such as smoking.
In the next installments of this blog, I’ll share some of the new information I learned in Pittsburgh in terms of diagnosis and new treatments. I hope you’ll check back.