n.
The act of measuring with a tonometer;
| Dictionary: To·nom·e·try |
The act of measuring with a tonometer;
| 5min Related Video: Tonometry |
| Medical Test: Tonometry |
| Where It's Done | Who Does It | How Long It Takes | Discomfort/Pain |
| Doctor's office, optometrist's office, or hospital. | Ophthalmologist or optometrist or ophthalmic nurse or technician. | 1-2 minutes. | None. |
| Results Ready When | Special Equipment | Risks/Complications | Average Cost |
| Immediately. | One of three kinds of tonometers: indentation, applanation, and noncontact or air puff. | The indentation or applanation (contact) tonometers can cause corneal abrasions. | $ |
None.
PurposeThe pressure of the aqueous fluid inside the eyes is measured.
PreparationA topical anesthetic is applied to the eyes.
Test procedureAn irregularly shaped cornea requires a special tonometer.
InterpretationPressure readings are in millimeters (mm) of mercury (Hg). A normal reading is about 20 mm Hg or lower. Higher readings may indicate either glaucoma or ocular hypertension.
AdvantagesOther tests may be necessary to diagnose glaucoma; these include visual field tests and ophathalmoscopy to evaluate the optic nerve.
The next stepRepeat tonometry or other tests may be necessary to distinguish between glaucoma and ocular hypertension or to assess borderline cases.
| Veterinary Dictionary: tonometry |
Measurement of tension or pressure, e.g. intraocular pressure. See also tonometer.
| Wikipedia: Tonometry |
In music, a tonometer is an instrument used to determine the pitch or vibration rate of tones, such as a tuning fork.
Tonometry is the measurement of tension or pressure [1]. A tonometer is an instrument for measuring tension or pressure [2].
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.
Contents |
A special disinfected prism is mounted on the tonometer head and then placed against the cornea. The examiner then uses a cobalt blue filter to view two green semi circles. The force applied to the tonometer head is then adjusted using the dial until the inner edges of these green semi-circles meet. Because the probe makes contact with the cornea, a topical anesthetic, such as oxybuprocaine, tetracaine, proparacaine (alcaine) or proxymetacaine is introduced onto the surface of the eye in the form of an eye drops.
Dynamic contour tonometry (DCT) is a novel method which uses principle of contour matching instead of applanation. This is designed to reduce the influence of biomechanical properties of the cornea on measurement. These include corneal thickness, rigidity, curvature, and elastic properties. It is less influenced by corneal thickness but more influenced by corneal curvature than the Goldmann tonometer.[4]
The PASCAL tonometer is currently the only commercial DCT tonometer available. It uses a miniature pressure sensor embedded within a tonometer tip contour-matched to the shape of the cornea. The tonometer tip rests on the cornea with a constant appositional force of one gram. When the sensor is subjected to a change in pressure, the electrical resistance is altered and the PASCAL's computer calculates a change in pressure in concordance with the change in resistance.
The contour matched tip has a concave surface of radius 10.5 mm, which approximates to the shape of a normal cornea when the pressure on both sides is equal. The probe is placed adjacent to the central cornea (see gallery) and the integrated piezoresistive pressure sensor automatically begins to acquire data, measuring IOP 100 times per second. A complete measurement cycle requires about 8 seconds of contact time. During the measurement cycle, audio feedback is generated, which helps the clinician maintain proper contact with the cornea. The device also measures the variation in pressure that occurs with the cardiac cycle. Literature references: [5][6][7]
Diaton tonometer (BiCOM, Inc) Transpalpebral tonometry refers to methods of measuring intraocular pressure through the Eyelid. The Diaton tonometer calculates pressure by measuring the response of a free falling rod, the principle is based on Newton's second law, as it rebounds against the tarsal plate of the eyelid. The patient is positioned so that the tip of the device and lid are overlying sclera. [8]. Transpalpebral tonometry does not involve contact with the cornea and does not require sterilization of the device or topical anesthetic during routine use. Diaton measurements show only moderate correlation with those provided by applanation tonometry and the device seems to be more affected by the corneal thickness than Goldmann tonometry. [9] The Diaton tonometer was preceded by the TGDc-01 which was discontinued in 2001.
Rebound tonometers ([Icare Tonometer http://www.icaretonometer.com]) determine intraocular pressure by bouncing a small plastic tipped metal probe against the cornea. The device uses an induction coil to magnetise the probe and fire it against the cornea. As the probe bounces against the cornea and back in to the device it creates an induction current from which the intraocular pressure is calculated. The device is simple, cheap and easy to use. It is portable, does not require the use of eye drops and is particularly suitable for children.
|
||||||||||||||||||||||||||||||||||||
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
| Intraocular Pressure (in medicine) | |
| tonometer | |
| Sclerostomy (surgical term) |
| What is tonometry? | |
| What does tonometry measures? |
Copyrights:
![]() | Dictionary. Webster 1913 Dictionary edited by Patrick J. Cassidy Read more | |
![]() | Medical Test. The Patient's Guide to Medical Tests by Faculty Members at The Yale University of Medicine and G.S. Sharpe Communications, Inc. Copyright © 1997 by Yale University of Medicine and G.S. Sharpe Communications, Inc. Published by Houghton Mifflin Company. All rights reserved. Read more | |
![]() | Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more | |
![]() | Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Tonometry". Read more |
Mentioned in