applanation tonometer ophthal.pptx
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Applanation tonometry measures intraocular pressure by flattening a fixed area of the cornea. Goldmann applanation tonometry, introduced in 1954, is the gold standard. It uses a double prism mounted on a slit lamp to applanate a 3.06mm diameter area of the cornea. The force required is measured and multiplied by 10 to obtain the IOP. Perkins and pneumatic tonometers also use applanation but are handheld. Non-contact tonometry uses a puff of air to momentarily deform the cornea and measure the required force without touching the eye.
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This document discusses various methods for measuring intraocular pressure (IOP), including direct and indirect techniques. Direct manometry involves inserting a needle into the eye, while indirect methods include indentation tonometry using the Schiotz tonometer, various types of applanation tonometry (Goldmann, Perkins, pneumatic, Tono-Pen), and non-contact tonometry. Factors like ocular rigidity, corneal thickness and curvature can influence tonometry readings. Newer methods like the dynamic contour tonometer and ocular response analyzer aim to provide measurements less affected by corneal properties.
Tonometry
This document discusses various techniques for measuring intraocular pressure (IOP), including manometry, digital tonometry, Schiotz tonometry, Goldmann applanation tonometry, non-contact tonometry, and Pascal's dynamic contour tonometry. It provides details on the principles, procedures, advantages, and limitations of each technique. Goldmann applanation tonometry remains the gold standard method, though newer techniques like Pascal's dynamic contour tonometry may provide a more accurate measurement by reducing the influence of corneal biomechanical properties. An ideal tonometer would accurately measure IOP, be convenient and easy to use, and not be affected by factors like corneal thickness.
Tonometer ppt
This document discusses different types of tonometers used to measure intraocular pressure. It describes indentation tonometers like the Schiotz tonometer which measures indentation depth from a known weight. Applanation tonometers like the Goldmann tonometer flatten a circular area of the cornea to measure pressure. Non-contact tonometers use an air puff to detect inward and outward corneal movement at different pressures. Accuracy can be affected by corneal properties, accommodation, and proper technique.
Tonometry and tonography
Tonometry is the measurement of intraocular pressure (IOP) inside the eye. There are several types of tonometers that use different principles like indentation, applanation, and contour matching. The Goldmann applanation tonometer is considered the gold standard. It works by applanating the cornea with a known force and area to indirectly measure IOP. Tonography provides additional information about aqueous humor dynamics by recording IOP changes over time using an electronic Schiotz tonometer. Newer dynamic contour tonometry matches the probe contour to the cornea to reduce deformation compared to applanation tonometry.
tonometry-140624223245-phpapp02-converted.pptx
This document discusses various methods for measuring intraocular pressure (IOP), including direct and indirect techniques. It describes manometry and tonometry in detail. For tonometry, it covers indentation tonometry using the Schiotz tonometer, various types of applanation tonometry including Goldmann, Perkins, pneumatic, and non-contact tonometers. It discusses the principles, techniques, advantages, limitations and sources of error for different tonometry methods. Newer tonometers like dynamic contour and ocular response analyzer are also summarized.
Part_1a.ppt
This document discusses general concepts of biomedical instrumentation and provides examples of direct and indirect measurement methods. It describes direct measurement using a clinical thermometer and indirect non-contact measurement using an infrared pyrometer. It also discusses direct measurement of intraocular pressure using a Goldmann applanation tonometer and indirect measurement using a non-contact air puff tonometer. Finally, it introduces a new direct measurement technique for intraocular pressure using a rebound tonometer that provides a more patient-friendly alternative.
Tonometry
every damn thing about Tonometry , my references are many ppts and websites ,Hope u find importance when u have ophtha seminar .Thank you
tonometry-140624223245-phpapp02.pptx
Tonometry is an indirect method to measure intraocular pressure. The two main types are indentation tonometry and applanation tonometry. Indentation tonometry uses a Schiotz tonometer which indents the eyeball with a plunger. Applanation tonometry flattens a part of the cornea and measures the force required using Goldmann, Perkins or pneumatic tonometers. Accuracy can be affected by factors like corneal thickness, rigidity and astigmatism. Regular calibration is needed to ensure precision of tonometry measurements.
IOP measurements
Intraocular pressure
Intraocular pressure (IOP) is the fluid pressure inside the eye. . IOP is an important aspect in the evaluation of patients at risk of glaucoma.
Tonometry is the method eye care professionals use to determine this. Most tonometers are calibrated to measure pressure in millimeters of mercury (mmHg).
Physiology
• Intraocular pressure is determined by the production and drainage of aqueous humour by the ciliary body and its drainage via the trabecular meshwork and uveoscleral outflow. The reason for this is because the vitreous humour in the posterior segment has a relatively fixed volume and thus does not affect intraocular pressure regulation.
• The intraocular pressure (IOP) of the eye is determined by the balance between the amount of aqueous humor - that the eye makes and the ease with which it leaves the eye.
The Goldmann equation states:
Po = (F/C) + Pv
Po is the IOP in millimeters of mercury (mmHg),
F is the rate of aqueous formation,
C is the facility of outflow,
Pv is the episcleral venous pressure.
Measurements
Intraocular pressure is measured with a tonometer as part of a comprehensive eye examination.
Types of Tonometry
1. Applanation tonometry
Applanation tonometry is based on the Imbert-Fick principle, which states that;
‘’The pressure inside an ideal dry, thin-walled sphere equals the force necessary to flatten its surface divided by the area of flattening’’
P = F/A
where P = pressure, F = force and A = area
In applanation tonometry, the cornea is flattened and the IOP is determined by varying the applanating force or the area flattened.
Goldmann and Perkins applanation tonometry
Equipment
• Tonometer, either Goldmann (used on slit lamps) or Perkins (hand-held)
• Applanation prism
• Local anaesthetic drops
• Fluorescein strips
• Clean cotton wool or gauze swabs.
Method
• The Goldmann applanation tonometer measures the force necessary to flatten an area of the cornea of 3.06mm diameter. At this diameter, the resistance of the cornea to flattening is counterbalanced by the capillary attraction of the tear film meniscus for the tonometer head.
• The IOP (in mm Hg) equals the flattening force (in grams) multiplied by 10. Fluorescein dye is placed in the patient’s eye to highlight the tear film. A split-image prism is used such that the image of the tear meniscus is divided into a superior and inferior arc. The intraocular pressure is taken when these arcs are aligned such that their inner margins just touch.
• Applanation tonometry measurements are affected by the central corneal thickness (CCT). When Goldmann designed his tonometer, he estimated an average corneal thickness of 520 microns to cancel the opposing forces of surface tension and corneal rigidity to allow indentation. It is now known that a wide variation exists in corneal thickness among individuals. Thicker CCT may give an artificially high IOP measurement, whereas thinner CCT can give an arti
tonometer.pptx
The document provides information about different types of tonometers used to measure intraocular pressure. It discusses the history and principles of direct tonometers like the manometer and indirect tonometers including indentation, applanation, pneumatic, Tono-Pen, rebound, and non-contact air puff tonometers. Details are given on the procedure, advantages and disadvantages of Schiotz indentation, Goldman and Perkins applanation, pneumatic, Tono-Pen, rebound and air puff tonometers.
Tonometry
This document provides a history of tonometry and describes various types of tonometers. It begins by outlining the development of early indentation and applanation tonometers in the 19th and 20th centuries. It then classifies tonometers and describes several popular models, including the Schiotz, Goldmann, and TonoPen tonometers. The document discusses the principles, techniques, sources of error, and disinfection methods for some of these instruments. It also introduces newer non-contact tonometry techniques like the Ocular Response Analyzer and Pascal tonometer.
Iop
The document discusses intraocular pressure (IOP) and methods of measuring IOP (tonometry). It defines IOP as the fluid pressure inside the eye and notes the normal range is 10.5-20.5 mmHg. Factors that can influence IOP include heredity, age, drugs, and blockage of aqueous circulation. Common tonometry methods are discussed - indentation tonometry uses a plunger like the Schiotz tonometer, while applanation tonometry is based on flattening the cornea and includes Goldmann, Perkins, and air puff tonometers. Accurate IOP measurement is important for evaluating glaucoma patients.
Tonometry ppt
TONOMETRY • Tonometry is the procedure performed to determine the intraocular pressure (IOP).
3. CLASSIFICATION TONOMETRY DIRECT INDIRECT Indentation Applanation Manometer
4. APPLANATION Contact Non-contact Goldmann Perkins Air-puff Pulse air
5. INDENTATION TONOMETER • It is based on fundamental fact that plunger will indent a soft eye more than hard eye. • The indentation tonometer in current use is that of Schiotz . • It was devised in 1905 and continued to refine it through 1927.
6. PROCEDURE • Patient should be anaesthetising with 4% lignocaine or 0.5% proparacaine. • with the patient in supine position, looking up at a fixation target while examiners separates the lids and lower the tonometer plate to rest on the cornea so that plunger is free to move. •
Tonometry
This document summarizes the history and principles of tonometry. It discusses how William Bowman first used digital tonometry in 1826 to estimate eye tension. It then describes the development of early indentation and applanation tonometers from the 1860s onwards, culminating in Goldmann's constant-pressure applanation tonometer from 1954. The principles of indentation, applanation, and modified Imbert-Fick's law are explained. Common tonometry devices like Schiotz, Perkins, and Goldmann are characterized along with their procedures. Potential sources of error are also outlined.
Tonometry and tonography
This document discusses various methods of measuring intraocular pressure (IOP), including direct cannulation and indirect tonometry techniques. It provides details on Schiotz indentation tonometry, Goldmann applanation tonometry, pneumatic applanation tonometry, and tonography. It also mentions factors that can affect IOP measurements such as ocular anomalies, patient behavior, instrumentation errors, and operation errors.
Tonometry
1. Tonometry is a clinical technique that measures intraocular pressure (IOP) by assessing the combined resistance of the eye's coats and IOP. A tonometer is a device that measures pressure on the optic nerves from fluid in the eyes.
2. Normal IOP ranges from 10-21 mmHg but an IOP over 21 mmHg increases glaucoma risk. IOP fluctuates throughout the day and is affected by various physiological and pharmacological factors.
3. Common tonometry methods include applanation, indentation, and air puff non-contact tonometry. Applanation tonometry like the Goldmann tonometer is currently the gold standard but techniques like Perkins, Tono-Pen, Sch
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applanation tonometer ophthal.pptx
- 1. APPLANATION TONOMETER AND NON CONTACT TONOMETER SREELAKSHMI S
- 2. APPLANATION TONOMETER Applanation Tonometer is used to measure Intraocular pressure The concept of applanation tonometer was introduced by Goldmann in 1954 Principle: It is based on limbert fick‘s law which states that “The pressure inside the sphere is equal to force required to flatten its surface divided by area of its flattening”
- 3. Types of applanation tonometer • Goldmann’s tonometer • Perkins applanation tonometer • Pneumatic tonometer • Tonopen
- 4. Goldmann’s applanation tonometer It is the most popular and accurate tonometer It consists of a double prism mounted on a standard slit lamp. Two extra forces acting on cornea • Capillary attraction of tear meniscus(T),tends to pull tonometer towards cornea • Corneal rigidity(C) resists flattening
- 5. • These two forces cancel each other when flattened area has a diameter of 3.06 mm • Applanation tonometry displaces only about 0.5 microlitre of aqueous humor , which raises IOP by about 3%.Because the volume displaced is so small , ocular rigidity , or stretchability of the globe has little effect on pressure reading
- 7. TECHNIQUE • Cornea is anaesthetised using 2% Xylocaine • Tear film is stained with fluorescein • Now the patient is made to sit in front of the slit lamp • The cornea and biprisms are illuminated with cobalt blue from the slit lamp
- 8. • Biprism is then advanced until it touches the apex of cornea • At this point two fluorescent semicircles are viewed through prism • Then the applanation force against cornea is adjusted until the inner edges of two circles meet • This is endpoint • The intraocular pressure is determined by multiplying dial reading with ten
- 12. Perkins applanation tonometer This is a handheld tonometer utilizing the same biprism as in the Goldmann tonometer. Advantages: It is small ,easy to carry and doesn’t require slit lamp. Disadvantages: It requires practice before reliable readings are obtained
- 15. In pneumatic tonometer cornea is applanated by touching the apex of the sialistic diaphragm by covering the sensing nozzle (which is connected to the central chamber containing the pressurised air) In this tonometer there is pneumatic to electronic transducer, which converts the air pressure recording on a paperstrip from where iop is read
- 16. TONOPEN • It is a computerised pocket tonometer • It employs a microscopic transducer which applanates the cornea and converts IOP into electric waves.
- 17. NON CONTACT TONOMETER • It is a fast and simple way to screen for high intra ocular pressure. • Introduced by Grolman. • PRINCIPLE OF NCT : A puff of air creates a constant force which momentarily deforms cornea. It is difficult to determine the exact nature of corneal deformation, although it is postulated that the central cornea is flattened at the moment the pressure measurement is made.
- 18. Types of NCT • 1. Table mounted – Xpert NCT. • 2.Hand held – Pulsair tonometer from Keeler.
- 19. Parts of NCT • 1. Alignment system – allows operator to optically align the patients cornea is 3 dimensions – axial, vertical and lateral. • 2.Monitoring system – consists of transmitter, detector and receiver. • 3.Pneumatic system- generates a puff of air which is directed against the cornea.
- 20. THANK YOU