tonometry
DESCRIPTION
TonometryTRANSCRIPT
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By. Chittranjan kumar Enternship
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Definition :- It is the procedure performed to determine the intraocular pressure (IOP)
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Def. of Glaucoma It is the characteristic and progressive condition of the eye which is raised the intraocular pressure occurs progressively damage the optic nerve fibers due to gradually loss of vision.
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Direct Indirect
Manometer
DIGITAL INDETATION(Schiotz)
APPLANATION
(Goldman)
NCT
Types of Tonometer
Perkin’s
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DirectTonometery
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Procedure:- -Cannula inserted into the the
Eye -Then connected to a tube of
calibrated in cm of water or mercury(mmhg)
Disadvantage :- -Not clinical method - Needs Anaesthesia
Manometry
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Indirect Tonometery
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Principle:-
-Based on Palpation By the Examiner
Procedure:- -Pt looks Down -Index finger of both hand used one
finger push eye ball above tarsal plate that time other finger palpation the process.
Digital Tonometry
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Advantage :- -Easiest -No equipment -No anaesthesia -No staining Disadvantage:- -Reading not proper -Only depend on examiner -Miner IOP can’t judged
properly
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Indentation tonometer (Schiotz)Principle:- - Amount of the indentation depends upon IOP
-The higher IOP the lesser
Indentation -The lesser theIOP the deeper the indentation
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-Less reading on scale ---- High IOP
-Scale reading have to be converted to IOP by the help of chart (Friedenwald conversion table)
HENCE
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Plunger of tonometer Indenting the cornea
Base plate of tonometer resting on cornea
Fig.1 In this cornea is indented
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PART OF SCHIOTZ TONOMETER
scale
Needle
Weight 5.5g plunger
Holder
Foot plate
lever
Additional weights 7.5,10,15g
Pseudocornea
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Process :- -Patient in supine position - 4%lignocaine/proparacaine -looking up at a fixation targetAdvantage:- - Fast - Very good to camp screening
- Portable - Cheep - Easy to cleaning &
maintenance - No required Slit lamp /
electricity
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Disadvantage :- - Reading effect by corneo scleral rigidity
- Can not be done in injury cases/early post-op
Cleaning& Mantanance:- - Cleaning after the removed from
barrel with
> Alcohal > Methylated spirt
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Calibration:- This instrument should be calibrated before each use by placing on pseudo cornea and be sure checking scale reading is zero.
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Applanation tonometer Principle:- -Applanation tonometer based on IMBERT FICK LAW
- Biprism tip flattens - A Biprism convert applantion area into half alignment of 2 half give the correct IOP reading
- Applanates a small area of cornea central 3.06mm.
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F- ForceA- Flattening of the areaP- Pressure in side the Eye
IMBERT FICK LAW
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Parts of Applanation tonometer
Biprism (measuring prism)Feeder arm
Housing
Adjusting knob
Connects to the slit lamp
Control weight insert
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Equipment:- -Housing control the prism
movement-Neck-Biprism plastic Biprism with
a mirror to slit corneal applantion image to 2 halves
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Process:--slit lamp-4% xylocaine -Dark room- Flurosceine stain of tear
film-Cobalt blue light -Biprism applanation cornea
with knobs reading at (1)-Reading read on knobs
scale multiplied by 10 ====IOP
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Advantage:–
- Most accurate . -No indentation so not
much force applied on cornea. -Does not effect by
cornea scleral rigidity . -Reading directly read
from knob . -Can be done on post op case /injury cases .
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Disadvantage :-
-Need slit lamp -Dark room .
- Need staining cobalt light
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Calibration:-◦ Appl, tonometer is calibrated with calibration bar.
◦ It should be done once in a weekly or monthly depend upon uses.
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NON CONTACT TONOMETER
Principle :-
A puff of air creates a constant force that momentarily flattens the cornea and internal reference point to the movement of flattening is measured and converted into IOP .Directly reading on display.
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Fig:- NCT
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Process:-
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ADVANTAGE ;- -Quick . -No anesthetic required
. -May be delegated . -Nothing contact to the
Eye .
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DISADVANTAGE :- -Expensive . -Difficult on to obtain reading
on scarred cornea , soft Eye -Not partable ..
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Perkins TonometerIt uses the same biprism as the Goldmann
applanator.
The light source is powered by battery.
The readings are consistent and compare quite well with the Goldmann applanator.
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