Q: What is high eye pressure and why does it cause damage?
A: Because the eyeball is filled with fluid it has an “intraocular pressure” which is determined by how much fluid is inside the eye.The range of pressure we describe as “normal” is anywhere between 10 and 21 mmHg (eye pressure is measured in millimetres of mercury just like blood pressure). High eye pressure is caused by an imbalance between the production and drainage of the fluid in the eye (aqueous humour) so that the fluid tends to build up. Loss of vision from glaucoma occurs when the eye pressure becomes too high for an individual eye and damages the optic nerve.
Q: I have increased eye pressure, does that mean I have glaucoma?
A: Not necessarily. Increased eye pressure (also termed ocular hypertension), means you are at risk but not all instances of increased eye pressure lead to glaucoma. You may be classed as a glaucoma suspect. A person has glaucoma if there is damage to the optic nerve. Increased eye pressure is a significant risk for the development of glaucoma.
Q: Will I develop glaucoma if I have increased eye pressure (ocular hypertension)?
A: The level of eye pressure at which there is progressive damage to an optic nerve varies between people, not everyone with high eye pressure develops the disease, although ocular hypertension is the most important risk factor for glaucoma.
Q: Can you have glaucoma without high eye pressure?
A: Yes. Some individuals with “high” pressures do not develop nerve damage, while others with “normal” pressures develop progressive nerve damage. In low-tension or normal-tension glaucoma the optic nerve is damaged even though the pressure in the eye is not very high.
Q: My doctor never tells me what my eye pressure is, saying she is “satisfied”. Should I know my pressure?
A: Deciding what level of eye pressure is acceptable for an individual is complex. Your specialist will assess a range of factors, including the eye pressures prior to treatment, how much optic nerve damage is already present and whether the damage is getting worse. These factors are then balanced against any possible risks or side effects associated with an increase in treatment. Your target pressure range may change with time and it is more important that you talk to your doctor about the process of decision making in your particular situation, rather than being too focused on one particular number.
Q: I have high eye pressure and I heard that my sleeping position may have an effect on it. Does it matter whether I lie flat or have high pillow?
A: Although eye pressure does change with posture, there is as yet no strong evidence that a particular sleeping position should be adopted by glaucoma patients. If an individual’s glaucoma is well controlled with no sign of deterioration, the goal of treatment has been achieved and there is no need to look to other lifestyle modifications such as altering sleep position. Adopting a new sleeping position may affect the quality of a night’s sleep and as yet there is insufficient evidence to recommend any change for glaucoma patients.
It is thought that the eye pressure goes up when we lie down and interestingly in some cases of normal pressure glaucoma the more severely affected eye seems to be on the side that the individual tends to sleep on - but this is not always the case, and as yet there is no firm evidence to guide any changed to sleeping habits.
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