A new Australian study has found some surprising factors which contribute to glaucoma and other pressure-related eye diseases.
Researchers from the University of New South Wales say the fluid pressure inside the eye increases - or spikes - during many everyday activities and rubbing the eyes, sleeping face down are just two of the ways of causing such eye pressure spikes.
There are many ways eye pressure spikes occur, including yoga head stands, weightlifting, playing instruments like the trumpet, swimming laps and gym workouts.
Professor Charles McMonnies from the UNSW School of Optometry and Vision Science, says any touching of the eye through the eyelids raises pressure - a light touch causes a small increase but a firm touch can cause a spike three to five times normal pressure.
Professor McMonnies says even wiping a watery eye and removing eye make-up both increase eye pressure, partly because they involve eye closure combined with lid contact and eye rubbing combines the effects of eye closure and rubbing forces on the eye and can raise pressure to very high levels - to as much as 10 times normal levels.
According to Professor McMonnies these pressure spikes are usually of little consequence and healthy eyes appear to be unaffected by them, but eye-pressure spikes that are large, last a long time or occur frequently, may contribute to the progression of pressure-related eye diseases.
McMonnies says 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.
Professor McMonnies advises that sleeping with the eyes in contact with a pillow or sleep mask should be avoided and may help to slow the progression of pressure-sensitive eye diseases.
Professor McMonnies also suggests modifying activities that may be dangerous, such as:- reading while in a sitting position as lying raises pressure - wiping watery tears 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 - and avoiding sleeping face down and pillow contact with the eyes - and treating itchy, dry, irritated eyes.
Those who are at risk of such pressure-related conditions are advised to avoid performing yoga headstands and find an alternative yoga procedures that do not involve body inversion.
Professor McMonnies says the risk of disease progression increases with the size, duration and frequency of the pressure spike and also increases with the number of years during which the activities causing the pressure spikes have been occurring.
The study is published in the journal Optometry and Vision Science.