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Too much pressure? Professor McMonnies

Normal activities such as wearing swim goggles, sleeping face down or doing a gym workout may contribute to glaucoma and other pressure-related eye diseases, a new study has found.

"The fluid pressure inside the eye increases - or spikes - during many everyday activities," says Adjunct Professor Charles McMonnies, of the UNSW School of Optometry and Vision Science, in a paper published in the journal Optometry and Vision Science.

"Eye rubbing, yoga head stands, weightlifting, sleeping face down, playing instruments like the trumpet and swimming laps are some of the many ways of causing eye pressure spikes," Professor McMonnies says.

Any touching of the eye through the eyelids raises pressure: light touch causes a small increase but firm touch can cause a spike three to five times normal pressure, he says.

Wiping a watery eye and removing eye make-up both increase eye pressure, partly because they involve eye closure combined with lid contact.

In the case of eye rubbing, the combined effects of eye closure and rubbing forces on the eye can raise pressure to very high levels; strong rubbing may raise pressure to 10 times normal levels.

"Normally these pressure spikes are of little consequence and healthy eyes appear to be unaffected by them. But eye-pressure spikes that are large, and/or last a long time, and/or occur frequently, may contribute to the progression of pressure-related eye diseases." These diseases include glaucoma - which affects a large proportion of elderly people and can lead to blindness - and rapidly increasing myopia, or short-sightedness. Rarer pressure-related conditions include keratoconus, or conical cornea.

"Avoiding sleeping with the eyes in contact with a pillow or sleep mask may help to slow the progression of pressure-sensitive eye diseases," he says.

"Treating itchy, watery, dry or irritated eyes might be the key to avoiding eye rubbing-related pressure spikes. If you practice yoga exercises, you might be advised to avoid head stands.

"People who think they might be at risk in relation to these conditions should ask their eye care practitioner to advise them regarding the significance of pressure spiking activities."
 
POSSIBLE DANGERS FROM EYE RUBBING AND OTHER COMMON ACTIVITIES

Eye-pressure spiking is normal and mechanisms such as blinking, lying down, and deep breathing appear to be of no consequence because they cause eye pressure spikes that are small, and/or short, so that the eyes are completely unaffected.

However, other forms of pressure, especially those that cause large and/or prolonged pressure spikes, may contribute to the progression of eye diseases that involve eye pressure.

The risk of disease progression increases with the size, duration and frequency of the pressure spike. Risk also increases with the number of years during which the activities causing the pressure spikes have been occurring.

Fortunately, most of the activities that might be dangerous are avoidable or can be moderated successfully (see below).

Eye rubbing may cause the highest pressure spike but may be only a very occasional harmless event that doesn't last much longer than a few seconds. However, for some people, especially those with itchy eyes, eye rubbing can be a frequently repeated habit, with rubbing episodes lasting for minutes that continue to occur over many years.

Taking a deep breath results in a pressure spike of about 33%. If breathing out is restricted, the increase in pressure is greater. For example, people playing a high wind resistance instrument such as a trumpet, oboe, French horn or bassoon, especially when they play loud and/or high pitch notes, can more than double their eye pressure. Professional musicians have been found to be at slightly higher risk for loss of vision due to their increased hours of playing over many years. The risk could be significant for someone with glaucoma or a tendency to develop glaucoma.

The combination of strenuous muscular effort and breathing that is strained can raise pressure to high levels. One example is weight lifting, especially when lying on a bench to do bench presses. Another example is doing sit ups on a slant board, when the starting head position is well below the feet; or doing push-ups, especially when they are performed with feet raised.

Doing a yoga headstand may involve risk because eye pressure doubles with body inversion and a yoga headstand position may be maintained by some people for 20 minutes or more.

During sleep eye pressure rises about 33%. However, people who sleep face down with their face buried in their pillow or resting on an arm, are at risk for long periods of much higher pressure.

Even for those who lie on their sides when sleeping, there is the possibility of pillow contact on the eye lids and increased pressure for dangerously long periods through the night. Wearing a sleep mask that touches the eyelids can cause a similar problem.
 
WHAT CAN BE DONE TO REDUCE THESE RISKS?

People are advised to ask their eye care practitioner if they have any indications of them being at risk for exposure to increased pressure from spikes. Some people with diseases such as glaucoma, keratoconus (conical cornea) and progressive myopia (rapidly increasing shortsightedness) are possibly at risk for worsening their eye disease if they are frequently engaged in activities that raise their eye pressure. Avoiding these activities might be important.

• Lying down raises pressure and people who are at risk should always try to do their reading while in a sitting position;
• Wiping watery tears from the eyes is best done with a tissue held to the corner of the eye and pressed gently against the nose so that lid contact is minimized. The tears can be drained without actually applying force to the eye through the lids;
• Avoiding sleeping face down and pillow contact with the eyes is a good idea, but if sleeping on a side is preferred, avoiding any pillow contact on the eye lids is still important. Firmer pillows are easier to position appropriately to avoid eye contact;
• If an eye rubbing habit is in response to itchy, dry, irritated eyes, treatment of the cause of the itch, dryness or irritation should be maintained faithfully. Preventing or controlling the itch is important so that the stimulus for rubbing can be avoided;
• For some people who have been performing yoga headstands, a switch to any of the many other alternative yoga procedures that do not involve body inversion could be advisable.

Media contact:
UNSW Faculty of Science media liaison: Bob Beale 0411 705 435 bbeale@unsw.edu.au