Tonometers measure the pressure inside the eye to check for glaucoma and other eye conditions. There are several types, including those that touch the eye directly, those that touch the eyelid, and those that do not touch the eye at all. Factors such as cornea thickness and eye inflammation can affect accuracy.
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the tonometer is an instrument used to check the pressure exerted by the fluid
inside a person’s eyes in terms of millimeters of mercury (mmHg). This
it is done to make sure that the eyes and optic nerves are healthy. There are
several types, including those that touch the eyeball
directly, those that only touch the eyelid and those that do not touch
the eye at all. While most are usually very accurate, some things can
cause inaccurate readings.
Scope
The project
the eyes are filled with fluid, which puts pressure on the optic nerves
and the outside of the eyeball. This is called intraocular pressure
(IOP) and measures between 10 mmHg and 21 mmHg in most healthy humans.
Having an IOP that is too high is a very common sign of glaucoma, but it can also
be a symptom of an inflamed iris or retinal detachment. An IOP that is too low
it can be a sign that fluid is leaking from the eye or that the eye is not
producing enough liquid to keep up with normal drainage. this can
increase a person’s risk of cataracts and retinal detachment, and often does
leads to a decrease in vision. Optometrists often use tonometers for
screen for these conditions and monitor those with known eye problems,
particularly glaucoma.
Main types
Many
tonometers measure IOP by pressing or bouncing a device against the
cornea, which is the front part of the eyeball that covers the iris, the
pupil, and a small chamber containing fluid. Although these are a lot
commonly used, some people don’t like them because they usually require
the use of numbing drops in the eyes. Common types of
corneal contact tonometers include the
following:
Goldman:
This is considered the industry standard for tonometry and has been working since
touching the tip of the device to the cornea to measure IOP. This
process is called appianto. Perkins and Maklakov tonometers can also
be used to do this.PASCAL
Dynamic contour tonometer (DCT) – the device works from
placing a small pressure sensitive concave on the
cornea. Application-Pen/Accu-Pen:
This type is shaped like a pen and works by means of electronics
indentation tonometry, electronic IOP measurement
transducer.Icare:
This measures IOP by bouncing a small probe against the cornea. The
the recoil creates an induction current, which can be used to measure IOP.
This method is called rebound tonometry.Schiötz:
A device that works by means of impression tonometry, a process in
which the optician measures the depth of the imprint a little
the plunger does on the cornea.
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they are also devices that measure IOP through the
eyelid, instead of actually touching the cornea. The
the most common type is the Diaton tonometer, which works by bouncing a rod
out of the eyelid, then measure the resulting bounce. Some people
I prefer this method because it usually doesn’t involve anesthesia
drops.
Some
the tools work without touching the eye at all. This is known as
non-contact or “air puff” tonometry, since
most non-contact versions work by shooting a small puff of air at the
cornea, and then measure the force required to flatten it. Unlike most
corneal contact instruments, air-puff devices usually do not require an eye
drops and the results are available in seconds. Another type is an
Ocular Response Analyzer (ORA), which uses two puffs of air to measure
the difference between the pressure on the cornea as it is going inward
and then when it returns to its normal form.
Mitigating factors
The project
The accuracy of a tonometer reading can be affected by several factors.
People tend to have slight differences in the thickness and hardness of
their corneas, so a person with a particularly hard cornea may have a
abnormally high IOP reading but still be in good health. Other factors, such as
also diseases, eye inflammation, caffeine consumption or exercise
affect a person’s IOP. Eye doctors may find it difficult to obtain one
measuring whether the person moves during the procedure, that is
because Air puff, Icare or Diaton models are usually used for children,
people who feel uncomfortable with objects touching the eye and those who
prefer not to use eye drops.
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