Glaucoma is not a single disease. Rather, it is the end result of a variety of diseases which affect the eye. When these diseases produce glaucoma, they cause a progressive deterioration of the cells of the optic nerve, which carries the visual impulses from the eye to the brain. A brief explanation of how the eye works will help to clarify the nature of glaucoma.
Like a camera, the eye captures information about shape, color and movement and relays it in the form of impulses to the brain. Let’s look at the various parts of our camera – the eye.
THE STRUCTURE OF THE EYE
The outer, protective, white layer of the eyeball is called the sclera. The clear front portion of the sclera, through which light rays enter the eye, is called the cornea. It provides the eye with much of its light-focusing power. The colored portion of the eye, the iris, functions like the diaphragm of a camera, controlling the size of the pupil to regulate the amount of light entering the eye. After passing through the pupil, light passes through another transparent structure, the lens, which can change its shape and thickness to fine focus the image onto the retina. Light impulses are detected by the seven million rods and cones of the retina, which processes them into impulses which are delivered to the brain via the optic nerve. The brain processes these signals into a “picture,” or visual image.
The interior of the eye is filled with a jelly-like substance called vitreous. In the front of the eye a small compartment, the anterior chamber, is filled with watery fluid, or aqueous humor, which not only nourishes the cornea and lens but provides the necessary pressure to help maintain the eye’s shape. We call this pressure the intraocular pressure, or IOP. The aqueous humor is produced by a tiny gland, the ciliary body, which is located behind the iris. After nourishing the cornea and lens, it flows out through a very tiny spongy tissue, only one-fiftieth of an inch wide, called the trabecular meshwork. When this drain becomes clogged, aqueous humor cannot leave the eye as fast as it is produced. This causes the fluid to back up and pressure in the eye to increase.
When the IOP increases, the eye “gives” at the weakest point in the sclera, which is the site at which the optic nerve leaves the back of the eye.
As mentioned earlier, the optic nerve carries visual information to the brain. It is made up of over one million nerve cells. While each cell is several inches long, it is only about one twenty-thousandth of an inch in diameter. When the pressure in the eye builds, the nerve cells become compressed, causing them to become damaged and, eventually, to die. The death of these cells results in permanent visual loss. Early diagnosis and treatment of glaucoma can help prevent this from happening.
Primary open-angle glaucoma, or POAG, is the most common form of glaucoma in the United States. Approximately one percent of all Americans have this form of glaucoma, making it a major cause of blindness and visual disability. There are no symptoms associated with POAG -pressure in the eye rises slowly, without causing any pain – so that a person with POAG often does not realize that he or she is slowly losing vision until the later stages of the disease. However, by the time vision is impaired, the damage is irreversible. Only a complete eye examination can detect glaucoma before this stage is reached.
WHO IS SUSCEPTIBLE TO GLAUCOMA?
Everyone should be concerned about glaucoma and its effects. However, there are a few conditions related to this disease which tend to put some people at greater risk. These include:
- People with a family history of glaucoma.
- People of African American descent have four to six times the chance of developing POAG as do Caucasians. Damage from glaucoma occurs at lower pressures and progresses more rapidly.
- People who are nearsighted (need glasses to see at distance) are more likely to develop POAG. People who are farsighted (need glasses for near work) are more likely to develop another form of the disease, angle-closure glaucoma.
- People with diabetes, or who have had an injury to the eye, or have had long-term treatment with steroids, are also more susceptible to developing glaucoma.
MUSICIANS AND GLAUCOMA
It has recently been shown that musicians who play high-resistance wind instruments are significantly more prone to develop glaucoma. This is because blowing into high-resistance wind instruments produces a Valsalva maneuver. To experience a Valsalva maneuver, inhale deeply, put your thumb in your mouth, and try to blow out against your thumb while holding your nose closed and without letting any air out of your mouth. This results in transiently increased blood pressure, increased pressure in the chest cavity, increased cerebrospinal fluid (the fluid bathing the brain) pressure, and increased intraocular pressure. Retinal hemorrhages have been reported to occur with a Valsalva maneuver.
Prolonged high expiratory air resistance, such as is experienced by professional brass musicians, may be a risk factor for the development of glaucomatous optic nerve damage. A study by Dr. Theodore Krupin, in Chicago, demonstrated that professional brass musicians can generate significant increases in eye pressure while playing high-resistance and amplitude notes. The greatest increase in eye pressure (+49.1 percent) was observed in trumpet players. Smaller increases occurred in persons playing the alto saxophone, French horn and oboe. The IOP returns to normal after the musician stops blowing into the instrument. These players may be subject to “transient” (in terms of hours) periods of increased eye pressure during instrument playing.
No one knows just how common glaucoma is in high-resistance wind instrument players because it has not yet been studied. Musicians who have more than one risk factor for glaucoma are probably more susceptible. For example, a nearsighted African American professional trumpet player with a family history of glaucoma would have an incredibly high chance of developing glaucoma. The glaucoma study we plan to conduct hopefully will provide important data on this question.
THE GLAUCOMA STUDY
In an effort to determine how common glaucoma is among professional musicians, and to identify musicians who have glaucoma so that they can be treated before they develop significant visual damage, a study has been initiated by Dr. Kerline Marcelin, under the direction of Dr. Robert Ritch and with the assistance of Local 802 member Dean Pratt, a trumpet player. The first part of the study consists of having one’s eye pressure measured while playing an instrument. Measurements will be taken before, during and after playing a series of high-pitched notes at high volumes. Measuring IOP is a simple routine test, merely requiring an anesthetic drop to be placed in the eye.
The second part of the study involves scheduling a complete, complimentary eye examination to look for any evidence of glaucoma. This will consist of measuring visual acuity, a slit-lamp examination, and a visual field examination, all routine tests. The examinations will be performed free of charge at the offices of Glaucoma Associates of New York at the New York Eye and Ear Infirmary, 310 East 14th Street, Third Floor, South Building, under the direction of Dr. Robert Ritch.
Dr. Ritch is Professor and Chief of Glaucoma Service at the New York Eye and Ear Infirmary. To participate in this study, contact Kerline Marcelin, MD, at (212) 475-9297 or firstname.lastname@example.org, or contact Dean Pratt at email@example.com.