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- 1. 4/8/2020 INTRAOCULAR PRESSURE AND TONOGRAPHY MAAZ UL HAQ C.L gupta eye institute
- 2. INTRA OCULAR PRESSURE o Pressure exerted by intraocular contents on the coats of the eyeball. Or fluid pressure of the aqueous humor inside the eye o Maintained by a dynamic equilibrium between theAH formation,AH outflow, and episcleral venous pressure. o Normal IOP = 10.5 to 20.5 mm Hg, however mean pressure is 15.5±2.57 mm Hg 4/8/2020
- 3. FACTORS INFLUENCING THE INTRA-OCULAR PRESSURE A) Long term changes B) Short term changes I. Heredity II. Age III. Sex IV. Race V. Refractive error VI. Valsalva manoeuvre?? I. Systemic venous pressure II. Mechanical pressure on the globe III. Diurnal variation IV. Seasonal variation V. Systemic hyperthermia VI. Effects of general anesthesia VII. Effects of drugs VIII. Blockage of aqueous circulation 4/8/2020
- 4. Short term changes in the IOP 4/8/2020 I. SVP II. Mechanical pressure on the globe from outside initially raises the IOP by indentation but after some time due to aqueous outflow IOP returns to normal and by prolonged pressure decreases below the initial level III. Diurnal variation in IOP: <5mm Hg change in 24 hr period; > 8 mm Hg change is pathogenic Change probably related to aqueous production and not drainage IV. Seasonal variation: higher IOP in winter and lowest in summer V. Effects of general anesthesia: decrease the IOP VI. Alcohol, heroin: decrease the IOP. Howe ever tobacco smoking: raised the IOP
- 5. 4/8/2020 VII. Blockage of aqueous circulation: raise the IOP blockage may occurs at two places At the pupil At the angle of anterior chamber
- 6. DIGITAL TONOMETER CONTACT TONOMETER NON-CONTACT TONOMETER INDENTATION APPLANATION MANOMETRY TONOMETRY SCHIOTZ VARIABLE FORCE VARIABLE AREA GOLDMAN PERKIN’S MAKLAKOF F AIR-PUFF PULSEAIR PNEUMOTONOME TERS 4/8/2020
- 7. Manometry 4/8/2020 It is the direct measure of IOP. Needle is induced either into the anterior chamber or into the vitreous which is then connected with a suitable mercury or water monometer to measure the IOP Disadvantages: Not practical method for routine human beings Needs general anesthesia which has its other effect on the IOP
- 8. TONOMETRY Tonometry is the procedure to measure the intraocular pressure of an eye It is the most important technique in evaluation of glaucoma patients The instrument used to measure the IOP isTONOMETER
- 9. METHODS OF TONOMETRY Indentation tonometry Applanation tonometry
- 10. INDENTATION TONOMETRY Indentation tonometry is based on the fact that a plunger will indent a soft eye more than a hard eye Previously used tonometer was Schiotz tonometer which was invented in 1905
- 11. SCHIOTZ TONOMETER It consists of: • Handle (finger rest) for holding the instrument in vertical direction • Footplate which rest on cornea • Plunger which moves freely within a shaft in the footplate • Bent lever whose short arm rests on the upper end of the plunger and a long arm which acts as a pointer needle.The degree to which plunger indents the cornea is indicated by the movement of this needle on a scale. • Weight:A 5.5gm wt is permanently fixed to the plunger, which can be increased to 7.5 and 10 gm.
- 13. Procedures After anaesthetising the cornea with paracaine, patient is made to lie supine on couch and instructed to fix at a target on ceiling. Then the examiner separates the lids with left hand and gently rest the footplate of the tonometer vertically on the center of the cornea followed by the deflection of the needle, reading on the scale is recorded as soon as possible as the needle becomes steady.
- 14. Cont… If the scale reading is less than 3, additional weight should be added to make it 7.5gm or 10gm and then IOP is recorded from a conversion table. Advantage:it is cheap, handy and easy to use. Disadvantage:it gives a false reading when used in eyes with abnormal scleral rigidity.
- 15. Applanation Tonometry The concept of applanation tonometry was introduced by Goldmann in 1954. It is based on Imbert-Fick law which states that the pressure inside a sphere (P) is equal to the force (W) required to flatten its surface divided by the area of flattening (A), i.e P=W/A
- 16. Commonly used tonometer are Goldmann tonometer Perkin’s tonometer Pneumatic tonometer Air Puff tonometer Tono-pen
- 17. Goldmann Tonometer It is the most popular and accurate tonometer. It consists of a double prism mounted on a standard slit lamp.The prism applanates the cornea in an area of 3.06 mm diameter.
- 18. Techniques • After anaesthetising the cornea with paracaine and staining the tear film with fluorescien patient is made to sit in front of slit lamp. • The cornea and biprism are illuminated with cobalt blue light from slit lamp. • Then we will move the biprism forward until it touches the apex of cornea.At this point two semicircles are viewed through the prism. • Then the applanation force against the cornea is adjusted until the inner edges of the two semicircles just touch. This is the end point.
- 19. Perkin’s tonometer This is a handheld tonometer utilizing the same biprism as in the Goldmann tonometer. It is small ,easy to carry and does not require slit lamp. But it require considerable practice before, reliable reading can be obtained.
- 20. Advantage It does not require slit lamp. It is useful in patient who can not cooperate on slit lamp ex. Bedridden patient, small children. It is useful in Patients who has deep eyes where Goldmann tonometer can not reach.
- 21. Air puff tonometer (Non contact tonometer) It is a non-contact tonometer It uses a rapid air pulse to applanate the cornea. It is useful for measuring IOP in children and other non- compliant patient groups. It is accomplished without the instrument contacting the cornea which reduce the potential for disease transmission.
- 23. Tono-pen It is a computerized pocket tonometer. It employs a microscopic transducer which applanates the cornea and converts IOP into electric waves.
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