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Tonometry in ophthalmology
This document discusses intraocular pressure (IOP) measurement and different types of tonometry. It defines IOP and tonometry, and lists the normal IOP range. It describes the goldmann applanation tonometer as the gold standard method, which uses the Imbert-Fick principle to measure pressure based on the force needed to flatten a given area of the cornea. It also discusses schiotz indentation tonometry, rebound tonometry, and digital tonometry as alternative methods. The document provides details on using and disinfecting each type of tonometer, and lists some contraindications.
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Tonometry in ophthalmology
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- 2. Intraocular pressure • Whatis intraocular pressure? • What unit? • Normal range • Causes of abnormal measurement
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- 5. Factors that mayincrease IOP
- 6. Factors that maydecrease IOP
- 7. Tonometry • Definition Tonometry isthe measurement of intraocular pressure by a tonometer
- 8. Types of tonometer Applanationtonometer Indentation tonometer • Goldmann applanation tonometer • Perkins tonometer • Pneumatic tonometer • Tonopen • Noncontact(air-puff) tonometer • Schiotz tonometer
- 9. Goldmann applanation tonometer •‘GOLD STANDARD’ • Based on Imbert-Fick principle Pressure=force/area of flattening • Mounted on a slit-lamp biomicroscope
- 11. Parts of theinstrument 1.Tonometer tip 2. Metal rod 3. Housing 4.Force adjustment knob
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- 13. Disinfecting the applanatingtip • Remove the tonometer tip from the biprism after each use • Disinfect by swabbing the tip with a cotton- tipped applicator that has been soaked in isopropyl alcohol • Rinse the tip with water and dry with gauze.
- 14. Contraindications • Active infections •Recurrent corneal erosions • Corneal abrasions that are not healed
- 15. Schiotz indentation tonometry •Inexpensive, portable, easy to use instrument Advantages Disadvantages • Limited accuracy in conditions like high myopia, following surgery and corneal oedema • Uses the fact that a plunger will indent a soft eyeball more than a hard one
- 16. Parts of instrument Curvedmetal foot plate Metal plunger Frame with handles Variety of weights Numbered scale Indicator needle Hammer
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- 18. Disinfecting schiotz tonometer •Remove the plunger from the cylinder • Wipe the footplate and the plunger with the alcohol • Rinse the footplate and plunger with water and wipe it with gauze
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- 20. Rebound tonometry • bouncea magnetized probe off the cornea and detect the deceleration of the probe caused by the eye. • The deceleration is more rapid if the IOP is high and slower if the IOP is low. • The probes are disposable between patients, so, disinfection is not necessary Disadvantage of this tonometer is that it can only be used in an upright patient (the probe falls out if the instrument is facing downward)
- 21. Parts of reboundtonometer Display Selector button Measurement button Grip Forehead support Forehead supporting adjusting wheel probe
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- 23. Digital tonometry • Roughestimation of intraocular pressure by finger tips especially in uncooperative patients or in absence of instruments.
- 25. Recap • Name onecause of ocular hypotony • IOP is highest in the morning. T/F • Name one drug which can cause increased IOP • What is the gold standard instrument to measure IOP? • Name one contraindication for schiotz tonometer.
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