HW # 5
2004200456
Lim Myeong Jun
Contents
 Outline of Chapter 7
 Tonometry
 Non Invasive Measurement
 NIBP
 Matlab Exercise
 Reference
Outline of Chapter 7
 BP
Invasive BP
Non Invasive BP
 Tonometry
 Stethoscope
Tonometry
 Tonometry?
1. Tonometry is the measurement of tension or pressure .
2. A tonometer is an instrument for measuring tension or
pressure .
In ophthalmology, tonometry is the procedure eye care
professionals perform to determine the intraocular pressure
(IOP), the fluid pressure inside the eye. It is an important
test in the evaluation of patients with glaucoma. Most
tonometers are calibrated to measure pressure in mmHg.
Methods of Ophthalmotonometry
 Semicircles seen during Goldmann tonometry through slit
lamp
 Applanation tonometry measures intraocular pressure
either by the force required to flatten a constant area of the
cornea (e.g. Goldmann tonometry) or by the area flattened
by a constant force. Goldmann tonometry is considered to
be the gold standard in tonometry as it is the most widely
accepted method of determining intraocular pressure.
However Goldmann tonometry is also an inherently
imprecise measurement.
Methods of Ophthalmotonometry
 In Applanation tonometry, a special calibrated sterile
probe attached to a slit lamp biomicroscope is used to
flatten part of the cornea. Because the probe makes contact
with the cornea, a topical anesthetic, such as
oxybuprocaine, tetracaine, alcaine, proxymetacaine or
proparacaine is introduced onto the surface of the eye in
the form of one or a few eye drops. A yellow fluorescein dye
is used in conjunction with a cobalt blue filter to aid the
examiner in determining the IOP. Perkins tonometer is a
special type of portable applanation tonometer, which
allows measurement of IOP in children, patients unable to
cooperate for slit lamp exam, and in anesthetised patients.
Methods of Ophthalmotonometry
 Pneumotonometry, also known as non-contact
tonometry or air-puff tonometry, uses an instrument that
senses deflections of the cornea in reaction to a puff of
pressurized air. Although not considered to be the most
accurate way to measure IOP, it is often used as a simple
way to screen for high IOP. It is an easy way to test children.
Because non-contact tonometry is accomplished without
the instrument contacting the cornea the potential for
disease transmission is reduced.
Tonometry
Mass
P
Mass
P
F = Mg
Contact area : A
Given by mass of Mass is M(Known), and contact area is
A(measurable). Then we can calculate the pressure using
this formula.
Tonometry
Blow air
Air jet
Photo
sensor
When the air jet blow air, part of the cornea is flatten. In the same
time, the LED(Light Emitting Diode, Photo diode) emit light.
Then the light receiving element(Photo transistor) receive the
reflection light by part of the cornea(flat cornea).
Photo sensor
Epoxy resin
Lens
LED chip
Bonding
wire
Lead
frame
Cathode
Anode
Photo Diode
Emitter
Collector
Photo Transistor
Non Invasive measurement
 The noninvasive auscultatory and oscillometric
measurements are simpler and quicker than invasive
measurements, require less expertise in fitting, have
virtually no complications, and are less unpleasant and
painful for the patient. However, noninvasive methods may
yield somewhat lower accuracy and small systematic
differences in numerical results. Non-invasive
measurement methods are more commonly used for
routine examinations and monitoring.
NIBP
 NIBP(Non Invasive Blood Pressure)
NIBP
Pressure (mmHg)
120
(systol
e)
80
(diastol
e)
The shape of blood pressure
time
We can measure the shape of blood pressure by IBP(Invasive
Blood Pressure). NIBP measure only value of systolic
pressure and diastolic pressure.
NIBP
Blue line is Cuff pressure.
Red line is Blood pressure.
-2~3 mmHg
decrease
Start
Systolic
pressure
Diastolic
pressure
Finish
NIBP
 Measured scale of Blood pressure
Given by Vp = 40sin(2πt) + 80, f = 50Hz
Systolic Pressure
Diastolic Pressure
Two side of signal is difficult to measure. Because we always measure original
signal with noise.
Oscillometric method
 The electronic version of this method is sometimes used in
long-term measurements and general practice. It uses a
sphygmomanometer cuff like the auscultatory method, but
with an electronic pressure sensor (transducer) to observe
cuff pressure oscillations, electronics to automatically
interpret them, and automatic inflation and deflation of
the cuff. The pressure sensor should be calibrated
periodically to maintain accuracy.
Reference
 http://www.ebme.co.uk/arts/tonometry/index.htm
 http://www.google.co.kr
Thanks for your attention!!