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Tonometry

qumber: Defination;. Tonometry. Objective measurement of IOP based, most commonly, on the forces required to flatten the cornea,or the degree of corneal indention produced by a fixed force. qumber: Principle;. Applanation Tonometry. Imbert-Fick principle;

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Tonometry

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  1. qumber: Defination; Tonometry • Objective measurement of IOP • based, most commonly, on the forces required to flatten the cornea,or the degree of corneal indention produced by a fixed force.

  2. qumber: Principle; Applanation Tonometry • Imbert-Fick principle; • For an ideal dry thin walled sphere pressure inside sphere(P) equals the forces(F) required to flatten its surface divided by the area(A) of flattening • P=F/A

  3. Goldmann tonometer • IOP is proportional to; • Pressure applied to the globe(cornea) • Thikness of the walls of Globe(cornea & Which is variable) Very accurate variable-force tonometer consisting of double prism

  4. Why pressure does not rise with tonometer pressure The cornea being rigid resists flattening. Capillary attraction of the tear film meniscus pulls the tonometer towards the cornea Capillary attraction and corneal rigidity cancel each other Flattened area has diameter of 3.06mm

  5. Procedure • Topical anesthetics and fluorescein • Goldmann tonometer mounted on slit lamp • Two semicircles • The dial on tonometer rotated to align inner margins • Reading on dial noted

  6. Potential errors • Inappropriate fluorescein • Pressure on the globe • Incorrect calibration • Corneal pathology

  7. Other tonometer • The schiotz(cheep,easy,no slitlamp) • The perkins(hand held,goldmann prism) • The air-puff(non-contact,air jet,no anaesthesia,accurate only from low-to-middle range,startle patient with noise & apparent force • The pulsair 2000 keeler(handheld,noncontact,no noise,accurate as goldmann • The tonopen(compares goldmann,distorted,edematous cornea,bandage contact lens)

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