Can Eye Pressure Become Too Low To Cause Vision Problem?
Low eye pressure (Hypotony) refers to an eye condition where the eye pressure or intraocular pressure(IOP) of the eye is too low, potentially leading to vision-threatening problem.
There is a lot of variability in what pressure an eye can tolerate. But how low is too low? The average normal eye pressure is between 10 and 21 mmHg (millimeters mercury). When the eye pressure is consistently at 5 mmHg or below, that is generally considered to be a low eye pressure. There is a lot of variability in what pressure an eye can tolerate. Just as some eyes are more sensitive to high pressure, some eyes are more easily troubled by low pressures. So, rather than the pressure number, it is more important to know if the low pressure is causing problems with the eye structure or vision.
There are two ways low eye pressure (hypotony) can be described: statistically and clinically.
Statistically, an eye is considered to have hypotony when the eye pressure or intraocular pressure (IOP) is below 6.5 mmHg.
Clinically, hypotony occurs when eye pressure is low enough to cause vision loss.
Eye pressure, or IOP, is regulated by the aqueous humor. This is located near the front of the eye, between the cornea and iris. The IOP is regulated by a constant inflow and outflow of this aqueous humor.
When that pressure becomes too low, structures within the eye can become compromised. This can lead to vision loss and other complications.
The effects of low IOP vary from individual to individual. Some eyes may be particularly susceptible to low IOP. Others may hardly be affected. The rest fall somewhere in between.
How does low eye pressure affect the eye?
When the eye pressure is lower than the eye can tolerate, the effect is like a ball that doesn’t have enough air and parts of the ball can fold or collapse.
The symptoms of low eye pressure vary. Some individuals may not experience any symptoms at all, despite their low eye pressure. When symptoms of low IOP do appear, they can lead to vision loss or distortion. Low IOP may also cause an individual to be slightly more farsighted than before.
Low eye pressure is often associated with detachment of the choroid (the layer of the eye lying between the retina and sclera) and shallowing of the anterior chamber (the front inner part of the eye).
Low eye pressure can also cause abnormalities in the retina, lens and cornea. All of these changes in the eye can lead to decreased vision.
What causes the eye pressure to become low?
There are two principal causes of low eye pressure: a higher than normal outflow of aqueous humor and the underproduction of aqueous humor. Low IOP can also be caused by a combination of the two.
Low eye pressure due to increased aqueous outflow is the more common cause and can result from glaucoma surgery.
Low eye pressure due to underproduction of aqueous humor can be caused by eye inflammation. Certain aqueous suppressant medications can limit aqueous humor production and lead to lower IOP. In addition, ciliary body damage can decrease aqueous humor production.
How is low eye pressure treated?
Treatment for low eye pressure varies depending on its cause. The underlying goal for treatment is to raise the IOP.
