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What is Which of the following is used as self-tonometer? and explain in detail?
Ans. b. Rebound tonometer (Ref: Shields Textbook of Glaucoma 6/e p35: Diagnostic Procedures in Ophthalmology by H. V Neema and Nitin Neema 2/100)Rebound tonometer is used as self-tonometer.Rebound Tonometer/lmpact-Rebound TonometerA new handheld tonometer, the Icare tonometer is able to measure IOP without the use of topical anesthetic.IOP is determined by measuring the force produced by a small plastic probe as it rebounds from the cornea.The rebounded tonometer has been shown to have similar accuracy to the Tono-Pen, and it is comparable with Goldman for lOPs over a reasonable range in adults.The Icare tonometer proven valuable as a screening tool in childrenQ.The ability to evaluate IOP without the use of topical anaesthesia potentially provides the opportunity to monitor IOP at homeQ.TonometersIndentationApplanation* Measures amount of deformation of globe* Affected by scleral rigidity* Example: Schiotz* Measures flattening* Based on Imbert fick law* Two types:- Variable force (Goldman) - Variable area (Maktakov) Types of Tonometers* Goldmann: Gold standard* Perkins: Hand held tonometer* Draeger: Portable and counter balanced* Pulsair: Non-contact type, sterilization not required* Mackay-Marg:- Useful for scarred/irregular cornea - Accurate over soft contact less as well* Tono-pen: Hand held form of Mackay Marg* Pneumatic tonometer: Also useful for scarred or edematous cornea.* Maklakov: Variation in applanation surface, constant force rather than constant area application used.* Dynamic contour tonometry (Pascal):- Based on a totally different principle that by surrounding and matching the contour of a sphere, the pressure on outside equals pressure on inside.- Advantage: Not affected by corneal thickness* Diatontonometer: Penlikehandhelddevice, non -contact type.