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Definition: Tonometry is the procedure used to measure intraocular pressure (IOP) — the fluid pressure inside the eye. It helps in the diagnosis and management of glaucoma, ocular hypertension, and other eye diseases affecting the optic nerve and cornea. --- Purpose / Importance: Maintaining normal intraocular pressure (10–21 mmHg) is essential for the shape and function of the eyeball. If the pressure increases (as in glaucoma), it can damage the optic nerve leading to vision loss. Tonometry helps to: Detect abnormal IOP early. Monitor IOP changes after treatment or surgery. Evaluate the risk of developing glaucoma. --- Principle: The basic principle of tonometry is derived from the Imbert-Fick law, which states: The pressure inside a thin-walled sphere equals the force required to flatten its surface divided by the area flattened. In simple terms, by applanating (flattening) or indenting a known area of the cornea with a specific force, the intraocular pressure can be calculated. --- Types of Tonometry: 1. Indentation Tonometry: Measures IOP by indentation (pressing) the cornea. Example: Schiotz Tonometer. Principle: Higher IOP resists indentation; lower IOP allows deeper indentation. Requires patient to be in a supine position and uses weights to indent the cornea. 2. Applanation Tonometry: Measures the force needed to flatten a specific area of the cornea. Example: Goldmann Applanation Tonometer (GAT) – the gold standard. Based on Imbert-Fick law, gives highly accurate results. Usually performed at slit lamp using fluorescein dye and cobalt blue light. 3. Non-contact Tonometry (Air-puff): Uses a puff of air to flatten the cornea without touching it. No anesthesia or direct contact needed. Useful for screening and in infection control. 4. Dynamic Contour Tonometry (DCT): Uses a pressure sensor that matches the corneal contour to give continuous and accurate IOP reading. Minimizes corneal influence. 5. Rebound Tonometry (Icare): A small probe bounces against the cornea; the deceleration speed is used to calculate IOP. Portable, no anesthesia, and ideal for children or uncooperative patients. --- Procedure (Goldmann Applanation Example): 1. Instill fluorescein dye and topical anesthetic in the eye. 2. Adjust the slit lamp and blue light. 3. Align the tonometer prism with the cornea. 4. Observe the fluorescein semicircles and adjust the knob until their inner borders just touch. 5. Multiply the scale reading by 10 to get IOP in mmHg. --- Factors Affecting Tonometry: Corneal thickness (CCT): Thicker cornea = falsely high IOP; thinner cornea = falsely low IOP. Corneal curvature and elasticity. Patient’s position, blinking, and pressure on the globe. --- Precautions: Avoid pressing on the eyelids. Disinfect the tonometer tip after each use. Ensure correct calibration of the instrument. Do not perform on eyes with corneal ulcers . #iop #tonometer #tonometry #applanation #ind.
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Similar to Tonometry ppt_slide_Notes_download .pdf
Tonometry ppt_slide_Notes_download .pdf
- 1. Tonometry:- Measurement of intraOcular pressure. Presented by:- ANMOL SINGH BOPTOM 2K24 UPUMS SAIFAI ETAWAH
- 2. Introduction:- ● Tonometry =Measurement of intraocular pressure (IOP). ● Essential test in glaucoma diagnosis & management. . IOP balance between aqueous humor production & drainage.
- 3. Tonometry: ● Technique usedto determine the intraocular pressure by measuring the eye’s resistance to indentation or flattening.
- 4. Normal Intraocular Pressure:- ●Normal range: 10–21 mmHg ● Mean: 15–16 mmHg ● Variation: Diurnal (Morning > Evening by 3–6 mmHg)
- 5. Importance of IOPMeasurement:- ● Detects glaucoma early. ● Monitors response to therapy. ● Assists in postoperative evaluation. ● Helps in diagnosing ocular hypertension or hypotony.
- 6. Factors Affecting IOP:- ●Age ● Posture ● Heart rate, blood pressure ● Time of day ● Eye rubbing, squeezing ● Medications (steroids increase IOP)
- 7. Classification of Tonometers:- 1.Indentation tonometers (e.g., Schiötz) 2. Applanation tonometers (e.g., Goldmann, Perkins) 3. Rebound tonometers (e.g., iCare) 4. Non-contact tonometers (NCT) 5. Dynamic contour tonometer
- 8. Schiötz Tonometer –Introduction:- ● Most common indentation tonometer. ● Invented by Hjalmar Schiötz (1905). ● Used to measure IOP by indentation of cornea.
- 10. Schiötz Tonometer –Parts:- ● Plunger. ● Footplate. ● Scale & pointer. ● Weights (5.5g, 7.5g, 10g, 15g) Handle.
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- 12. Schiötz Tonometer –Procedure:- 1. Patient lies supine. 2. Instill topical anesthetic. 3. Place tonometer vertically on cornea. 4. Note scale reading. 5. Convert reading into mmHg using conversion chart.
- 15. Schiötz Tonometer – Advantages:- ●Simple and inexpensive. ● Portable. ● Useful for mass screening.
- 16. Schiötz Tonometer – Disadvantages:- ●Contact method → risk of infection. ● Requires supine position. ● Corneal thickness affects reading. ● Less accurate in irregular cornea.
- 17. Applanation Tonometry – Principle:- Basedon Imbert-Fick Law: ● Force required to flatten (applanate) a fixed area of cornea indicates IOP.
- 19. Types of ApplanationTonometers:- ● Goldmann Applanation Tonometer (GAT) ● Perkins Handheld Tonometer ● Tono-Pen ● Maklakoff tonometer
- 21. Goldmann Applanation Tonometer– Introduction:- ● Gold standard for IOP measurement. ● Mounted on slit lamp. ● Measures force to flatten 3.06 mm corneal area.
- 24. Goldmann Tonometer –Procedure:- 1. Use fluorescein dye and topical anesthetic. 2. Align blue cobalt light. 3. Adjust prism until two semicircles just touch. 4. Read IOP on drum scale (in mmHg).
- 26. Goldmann – Advantages ●Highly accurate. ● Most widely used. ● Minimal effect of corneal rigidity. Goldmann – Disadvantages ● Contact → requires sterilization. ● Affected by corneal thickness. ● Needs slit lamp setup.
- 27. Perkins Tonometer ● Portableversion of Goldmann. ● Handheld, battery-operated. ● Used in bedridden or pediatric patients. Tono-Pen ● Digital, handheld applanation tonometer. ● Requires minimal contact area. ● Displays digital IOP value.
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- 30. Non-Contact Tonometer (NCT):- ● Knownas “Air-Puff” tonometer. ● Uses puff of air to flatten cornea. ● No anesthesia needed. ● Ideal for screening & children.
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- 32. NCT – Advantages ●Non-contact, no infection risk. ● Quick & automatic. ● Comfortable for patient NCT – Disadvantages ● Expensive. ● Less accurate at extreme IOP values. ● Influenced by corneal thickness.
- 33. Rebound Tonometer (iCare):- ●Uses small magnetic probe that rebounds off cornea. ● No anesthesia needed. ● Portable and easy for home or pediatric use.
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- 35. Dynamic Contour Tonometer (Pascal):- ●Measures IOP independent of corneal thickness. ● Sensor tip matches corneal contour. ● Gives true IOP and ocular pulse amplitude.
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- 37. Sources of Errorin Tonometry:- ● Improper calibration ● Thick/thin cornea ● Poor fixation ● Excessive fluorescein ● Patient squeezing or blinking
- 38. Precautions (Do’s andDon’ts): Do’s: ● Clean prism before/after use. ● Use correct alignment. Don’ts: ● Don’t apply excessive pressure. ● Don’t use unsterile instruments.
- 39. Clinical Interpretation ● IOP<10 mmHg: Ocular hypotony. ● IOP >21 mmHg: Ocular hypertension. ● IOP >30 mmHg: Risk of optic nerve damage (Glaucoma).
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