tonometry

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TONOMETRY BY P. MAHALINGAM BVM06066 :TONOMETRY BY P. MAHALINGAM BVM06066

TONOMETRY :TONOMETRY In ophthalmology, tonometry is the procedure eye care professionals perform to determine the intraocular pressure (IOP), the fluid pressure inside the eye Tonometry is used to determine the pressure in the eye by measuring the tone or firmness of its surface.

Why It Is Done :Why It Is Done This test is used to check for glaucoma, GLAUCOMA; Is an eye disease that can cause blindness by damaging the nerve in the back of the eye (optic nerve). Damage to the optic nerve may be caused by a buildup of fluid that does not drain properly out of the eye

Tonometry methods :Tonometry methods Applanation (Goldmann) tonometry; This type of tonometry uses a small probe to gently flatten part of your cornea to measure eye pressure and a microscope called a slit lamp to look at your eye. The pressure in your eye is measured by how much force is needed to flatten your cornea.

A Goldmann tonometer :A Goldmann tonometer

Slit lamp of a goldmann tonometer :Slit lamp of a goldmann tonometer

Semicircles seen during Goldmann tonometry through slit lamp :Semicircles seen during Goldmann tonometry through slit lamp

Slide 9:This type of tonometry is very accurate and is often used to measure IOP after a simple screening test (such as air-puff tonometry) finds an increased IOP. Perkins tonometer is a special type of portable applanation tonometer,

Tonophen :Tonophen

Electronic indentation tonometry; :Electronic indentation tonometry; Electronic tonometry is being used more often to check for increased IOP. Although it is very accurate, electronic tonometry results can be different than applanation tonometry.

Slide 12:In this gently place the rounded tip of a tool that looks like a pen directly on cornea. The IOP reading shows on a small computer panel.

Noncontact tonometry (pneumotonometry); :Noncontact tonometry (pneumotonometry); Noncontact (or air-puff) tonometry does not touch your eye but uses a puff of air to flatten your cornea. This type of tonometry is not the best way to measure intraocular pressure. But it is often used as a simple way to check for high IOP and is the easiest way to test children.

Indentation (Schiotz) tonometry :Indentation (Schiotz) tonometry This type of tonometry uses a plunger to gently push on your cornea. The pressure in your eye is measured by how much weight is needed to flatten your cornea. This test is not as accurate as applanation tonometry and is not used very much by ophthalmologists and optometrists.

Slide 15:Schiotz Tonometer

Schitoz tonometer :Schitoz tonometer

Slide 17:It may also be used for people who have had laser-assisted in-situ keratomileusis (LASIK) surgery. Noncontact tonometry does not use numbing eyedrops.

Rebound Tonometry :Rebound Tonometry It used to determine intraocular pressure by bouncing a small plastic tipped metal probe against the cornea. The device uses an induction coil to magnetise the probe and fire it against the cornea. As the probe bounces against the cornea and back in to the device it creates an induction current from which the intraocular pressure is calculated.

Slide 19:It is portable, does not require the use of eye drops and is particularly suitable for children Palpation, also known as digital tonometry, is the method of estimating intraocular pressure by pressing gently against the cornea of a closed eye with your index finger.

How the Test is Performed :How the Test is Performed The applanation method measures the force required to flatten a certain area of the cornea. A fine strip of paper stained with orange dye is touched to the side of the eye. The dye stains the front of the eye to help with the examination, then rinses out with tears. An anesthetic drop is also placed in the eye.

Slide 21:A patient in front of a Tonometer

Slide 22:A local anesthetic eye drop, such as proparacaine, oxybuprocaine, tetracaine, proparacaine (alcaine) or proxymetacaine is introduced onto the surface of the eye in the form of an eye drops . It is used to numb the eyeball

Slide 23:An anesthetic drop is also placed in the eye. The slit-lamp is placed in front of you and you rest your chin and forehead on a support that keeps your head steady. The lamp is moved forward until the tonometer touches the cornea. The light is usually a blue circle.

Slide 24:The health care provider looks through the eyepiece on the lamp and adjusts the tension on the tonometer. There is no discomfort associated with the test. A slightly different method of applanation uses an object similar to pencil.

Slide 25:Again, you are given numbing eye drops to prevent any discomfort. The device touches the outside of the eye and instantly records eye pressure. The last method is the noncontact method (air puff). In this method, your chin rests on a padded stand

Slide 26:You stare straight into the examining device. The eye doctor shines a bright light into the eye to properly line up the instrument, and then delivers a brief puff of air at your eye. The machine measures eye pressure by looking at how the light reflections change as the air hits the eye.

Slide 27:A normal result means your eye pressure is within the normal range. Normal eye pressure range is 10 - 21 mmHg. Abnormal results may be due to: Glaucoma Hyphema

: High values A high IOP may mean that animal have glaucoma or that you are at high risk for developing glaucoma. Animal have ongoing pressures above 27 mm Hg usually develop glaucoma unless the pressure is lowered with medicines.

Slide 29:Animal have an ongoing IOP higher than 21 mm Hg but do not have optic nerve damage have a condition called ocular hypertension. It may be at risk for developing glaucoma over time.

Risks :Risks There is a very slight risk that cornea may be scratched during the methods that involve touching a tonometer to the eye. Rubbing of eyes before the anesthesia wears off increases the risk of scratching the cornea.

Slide 31:If tonometry causes a scratch on the cornea, the eye may be uncomfortable until the scratch heals, which normally takes about a day There is also a very small risk of an eye infection or an allergic reaction to the eyedrops used to numb on eyes.

Slide 32:With the air-puff (noncontact) method, there is no risk of scratches or infection, since nothing but air touches your eyes. But this method is not the best way to measure intraocular pressure.

What Does Tonometry Reveal? :What Does Tonometry Reveal? Tonometry measures intraocular pressure to diagnose glaucoma. Tonometry is also useful for identifying low IOP, which may occur with anterior uveitis Low IOP is also associated with dehydration.

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