الأجهزة البصرية Instrument optometry ،،،

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السلام عليكم ورحمة الله تعالى وبركاته ...


سنبدأ في هذا الركن بإذن الله تعالى في شرح الأجهزة البصرية وكيفية إستخدامهاا ومكوناتهاا

وأهميتهاا والأمراض التي تعالجهاا ...


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~~((( الأجهزة البصرية Instrument optometry ،،، )))~~
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تابعوناا وشآركوناا لو أحببتم ...


جزيتم الفردوس الأعلى ،،
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سنبدأ أولا ً بالحديث عن ال~((( Tonometry )))~


Goldmann tonometry >>>


Tonometry is the objective measurement of IOP, based,

most commonly , on the force required to flatten the cornea

or the degree of corneal indentation produced by a fixed force.
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Applanation tonometry is based on the Imbert_Fick principle

which states that for an ideal, dry, thin_walled sphere

the pressure inside the sphere (P) equals the force necessary

to flatten its surface (F) divided by area of flattening (A) (i.e

P = F / A ). The IOP is proportional to the pressure applied to

the globe (in practice the cornea) and the thickness of the

walls of the globe (i.e. the thickness of the cornea,which is

variable).

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The human eye is, however, not an ideal sphere __the cornea

is rigid and resists flattening. Capillary attraction of the tear

meniscus however, tends to pull the tonometer towards

the cornea. Corneal rigidity and capillary attraction cancel

each other when the flattened area has a dimeter of 3.06 mm

as in Goldmman tonometry. The Goldmann tonometer is a very

accurate variable _force tonometer consisting of a double

prism.
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Procedure >>>




1. Topical anaesthetic and fluorecein are instilled into the


conjunctival sac.


2. At the slit lamp, a Goldmann prism ( mounted on a
tonometer


is applied axially to the cornea surface.


3. A pattern of two semicircles will be seen, one above and one

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below the horizontal midline.
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manual_keratometer ....






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phoropter ...





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retinal_camera ...



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retinoscope ...



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4. The dial on the tonometer is rotated to align the inner

margins of the semicircles.


5. The reading on the dial, multiplied by 10. equals the IOP
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