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Normal Eye Pressure

Leena Palande Aug 1, 2020
Eye pressure is the pressure of aqueous humor, which is essential for normal functioning of the eye. This story discusses the intraocular pressure in detail.
A thick gelatinous fluid called aqueous humor is present in the space between the eye lens and the cornea. The pressure generated by this fluid inside the eye is known as eye pressure or intraocular pressure. Ophthalmologists measure it with the help of a tonometer. The intraocular pressure helps evaluate severity of situations like glaucoma.

Role of Aqueous Humor in Eye Health

Aqueous humor provides nutrition to the eyes. It is responsible for the typical convex shape of the eye (inflation of the eye). It also acts as an antioxidant. It helps prevent various eye diseases. The rate of production and drainage of aqueous humor plays an important role in maintaining normal intraocular pressure.
Even slightly affected production or drainage of aqueous humor can lead to significant changes in the pressure. Thus, an equilibrium between the rate of production and corresponding rate of drainage of aqueous humor is essential to maintain the normal eye pressure. Corneal thickness and rigidity also play an important role in measuring the eye pressure.

Intraocular Pressure (IOP)

The unit of measurement of eye pressure is 'millimeters of mercury' (mmHg), and the normal range of IOP is 10-20 mmHg. IOP higher than 20 mmHg, without optic nerve damage or loss of vision, is known as ocular hypertension (OHT). Average IOP is 15.5 mmHg; however, it is not constant.
Throughout the day and night, it may increase or decrease by about 2.75 mmHg. During daytime activities, it may increase or decrease by about 3-6 mmHg. The pressure below 12 mm Hg is considered low.
The condition wherein the IOP is equal to or lower than 5 mmHg is known as ocular hypotony. Such a low IOP suggests fluid leakage and deflation of the eyeball. Both high and low eye pressure can lead to pain behind the eye and headache.
Certain physical activities can affect the IOP temporarily, for example, standing on your head or lifting heavy objects. However, the IOP will soon return to its original level without causing any harm. The IOP varies according to heart rate, respiration, exercise, and fluid intake. Certain drugs and medications also influence the intraocular pressure.
Excess caffeine leads to high IOP, whereas alcohol abuse leads to low IOP. If high or low IOP continues to exist for a longer period of time, then it is considered harmful for the eye. Proper eye care can help prevent serious eye problems. Certain exercises like walking, jogging, running, yoga, and aerobics help lower the IOP.


Eye pressure is measured by various methods. One of the simplest way is described here. The patient is administered eye drops to numb the surface of the eye.
A hand-held device, which looks like a pencil, is used by the doctor to measure the intraocular pressure. The device records the pressure, as soon as it touches the eye. No pain or discomfort is experienced during this procedure.

Effects of Increased IOP

Ocular hypertension is one of the most important risk factors of glaucoma. Increased intraocular pressure, optic nerve damage, and vision loss are noticed in patients diagnosed with glaucoma.
Sometimes, difference in pressure between the two eyes is noticed, which can lead to certain types of glaucoma, iritis or retinal detachment, etc. Certain structural problems, genetic factors, certain medications, exercises, inflammation of the eye, etc., can result in OHT.
It is believed that psychological stress brings about changes in normal eye pressure. More studies are required to conclude about the effect of psychological stress on intraocular pressure. Those diagnosed with ocular hypertension are more closely monitored by the doctors for the onset of glaucoma.
Uncontrolled glaucoma can result in loss of vision and blindness. Therefore, it is necessary to consult an ophthalmologist immediately if you have any type of eye problem.
Disclaimer: This story is for informative purposes only, and should not be used as a replacement for expert medical advice.