IS DRINKING TOO MUCH WATER DANGEROUS FOR GLAUCOMA PATIENTS?

Ophthalmologist Carolina Valdivia, MD answers a question about whether drinking too much water dangerous for glaucoma patients.

Hi Dr. Valdivia,

My Mom is affected by glaucoma and the doctor is treating it with Travatan eye drops every day. I have been going through websites on glaucoma to try to understand this disease better. I read in one of them that "People affected by glaucoma should NOT take lot of water in the early morning with empty stomach."

Could you please let me know if this is correct? Is drinking too much water dangerous for glaucoma patients?

Your question relates to drinking too much water in the morning and its potential effects on glaucoma management. Specifically, does drinking too much water cause elevations in intraocular pressure that can lead to optic nerve damage? The general answer to this question is no. Excess daily fluid intake, including drinking too much water, can temporarily raise intraocular pressure in some individuals, but these are short-lived events and usually have no lasting effects. In glaucoma, it is controlling sustained increases in eye pressure that are the biggest challenge.

People diagnosed with glaucoma often present with wide fluctuations of intraocular pressure that are problematic. However, it is important to understand that people without any eye disease also experience eye pressure fluctuations throughout the day.

This is normal.

In persons with glaucoma, intraocular pressure fluctuations can be 6 mmHg or more. This is one of the main characteristics that ophthalmologists are trying to detect when we screen people for glaucoma using a tonometry test.

There is a clinical evaluation called the water drinking test, in which a person that is a glaucoma suspect fasts for at least three hours and then is asked to drink one liter of water in less than five minutes. Intraocular pressure measurements then are taken every 15 minutes. These are compared to previously obtained results for the patient. It has been observed that eye pressure in glaucoma suspects can be raised higher than 6 mmHg during this test.

Although the water drinking test can be useful at times, it has the drawback of being unreliable, in that it does not produce similar results when repeated in the same patient. A number of external factors potentially can affect the test, such as a person's body mass, age, degree of hydration, and the presence of systemic disease.

Unfortunately, some Internet websites have extrapolated the premise of the water drinking test to indicate that persons with glaucoma should not drink water in the morning or should avoid drinking too much water at any time during the day.

This is incorrect.

It points to a fundamental misunderstanding of the water drinking test and why it might be used in some patients that are glaucoma suspects.

• Individuals diagnosed with glaucoma, such as your mother, typically are placed on medications designed to lower intraocular pressure. Studies have shown that patients treated with these anti-glaucoma medications do not exhibit eye pressure spikes greater than 6 mmHg when administered the water drinking test. The drug Timolol, which your mother is not using, appears to be the least effective in controlling the spikes. However, this does not mean that Timolol does not control them at all. It simply does not do it as well as the other medications. The general conclusion is that there is little or no risk to your mother from drinking too much water as long as she is adhering to her medication regimen.
• Remember that the water drinking test is used with glaucoma suspects, individuals that have not yet been formally diagnosed with the disease, and that those under glaucoma treatment do not exhibit the spikes in eye pressure. If drinking water posed that much of a risk, it would be necessary to advise the entire population to restrict their daily fluid intake, particularly in the morning, in order to protect the few that might be glaucoma suspects. This not only would be impractical, it would be medically irresponsible.
• Studies have indicated that the spikes in intraocular pressure observed in some glaucoma suspects during the water drinking test are transient. Peak pressure is observed at 30 minutes (the second point at which the eye pressure is measured) and full recovery back to the original eye pressure occurs within 60 minutes. This period is too short to cause any real damage. If this was not the case, it would be irresponsible for ophthalmologists to perform the test in the first place.
• Virtually anything that places the body under stress can cause transient increases in eye pressure. Examples include wearing constrictive clothing or jewelry around the neck, intensive exercise or heavy lifting, caffeine intake, anxiety, and even holding your breath. But none of these things are sufficient to cause ocular pathology. The reason for this is that our bodies have a mechanism called homeostasis that always seeks to bring the body into balance. Without homeostasis, humans could not survive.
• Water is the principal chemical component in our bodies, comprising about 60 percent of total body weight. Every system in the body depends on water. For example, water flushes toxins out of vital organs, carries nutrients to your cells and provides a moist environment for eye, ear, nose and throat tissues. Restricting daily fluid intake can lead to chronic dehydration, a situation that can have severe health consequences.

Each day we lose water through breathing, perspiration, excreting urine, and bowel movements. For our body to function properly, we must replenish its water supply by consuming beverages and foods that contain water. Because of our body's homeostatic mechanisms, pinpointing when we are drinking too much water is a difficult task.

The following guidelines may help your mother to maintain a good daily fluid balance.

The average urine output for adults is about 1.5 liters (6.3 cups) a day. We lose close to an additional liter (about 4 cups) of water a day through breathing, sweating and bowel movements. Food usually accounts for 20 percent of our total daily fluid intake. Thus, if we consume 2 liters of water or other beverages per day (a little more than 8 cups) along with a normal diet, we typically will replace any lost fluids.

These guidelines apply to adults with a normal body weight, average activity level, and with no systemic disease. If any of these are different in your mother, adjustments may have to be made. For this reason, it is important to consult with her physician about what her daily fluid intake should be.

Your mother currently is under treatment with the glaucoma medication Travatan. This is a highly effective medicine that facilitates the exit of aqueous humor through the uveoscleral pathway, an alternative to the conventional route through the trabecular meshwork. Travatan also has been shown to be effective in controlling transient spikes in eye pressure. Thus, as long as your mother adheres to her prescribed glaucoma treatment regimen, you need not worry very much about her drinking too much water.

On the other hand, drinking large quantities of water in a short period of time can place the body in a temporary state of stress. This is the basis of the water drinking test. If you remain concerned, there are some simple steps that your mother can take to avoid drinking too much water in the morning. Upon waking, she can drink an 8 ounce (0.2 liter) glass of water. This amount will not cause stress to her body. Once she has eaten, she can take another cup of water if she wants and then continue her regular daily fluid intake according to her physician's recommendations.

A person should not restrict their daily fluid intake because they have glaucoma.

Having a family history of glaucoma is one of the main glaucoma risk factors. Although this does not guarantee that you will develop glaucoma, ophthalmologists recommend that persons in risk categories have their intraocular pressure monitored regularly as a precautionary measure.

Carolina Valdivia, MD

REFERENCE:

Khurana AJ. Comprehensive Ophthalmology, 4th Ed. New Delhi: New Age International (P), 2007:221.

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