Chapter 5 Pa Chyme Try

8/3/2019 Chapter 5 Pa Chyme Try

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Chapter Five

Dr. Genalin A. Ang


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` Measurement of the Central Corneal Thickness

` Relevance in many clinical situations such as:

` A. Pre-Operative assessment of refractive surgery

patients ( LASIK )` B. Diagnoses of corneal conditions , fitting of the

contact lenses

` C. The accurate assessment of intra ocularpressure

`


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` . However, if the cornea is thinner than normal,

then the eye will feel softer to the tonometer and

the measured reading will actually be falsely low

(i.e. the true pressure inside the eye is actuallyhigher than what is being measured)

` If the CCT is thicker than normal, then the eye

pressure number read by the tonometer, will be

falsely high (i.e. the machine thinks that the eyeis firmer (higher pressure) than it really is)


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` The surface of the eye (cornea) comes in different

thicknesses just like all parts of our body vary from

human to human.

` Devices that measure eye pressure (tonometers)are calibrated for the normal range of central

corneal thickness (CCT).


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` A child who has had cataract surgery comes to see their

eye doctor 6 months after surgery for a check-up.

` The eye doctor measures the eye pressure to be 30.

The rest of the eye exam is completely normal. The eye

has not gotten any bigger,

` the cornea is not cloudy, there is no swelling of the

cornea (corneal edema), and the optic nerve shows no

cup. In other words, there are absolutely no signs of

glaucoma.` But what about the high pressure of 30? The doctor

measures the patients CCT to be well above normal.


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` Therefore, the doctor may safely conclude that

this child does not have glaucoma and that the

elevated pressure reading is an artifact brought on

by the thicker cornea often seen in children whohave had cataract surgery.

` Management : The doctor probably should not be

absolutely certain and dismiss this outright.


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` It may be more prudent to see this child again in

the not too distant future to recheck the value and

make sure that none of the other signs of

glaucoma (e.g. optic nerve cupping


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` A Child with severe congenital glaucoma has a

routine follow-up examination.

` The child is on 3 different antiglaucoma eye drops,

and has a pressure of only 15. Is the glaucomawell controlled? The CCT turns out to be low (thin

cornea), and the optic nerve cup is bigger than the

last visit. It may very well be that the glaucoma is

not adequately controlled and that the pressurereading is a falsely low value due to the thin

cornea. Further treatment may be required.


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` The use of corneal pachymetry in the

management of patients at risk for or with

glaucoma is becoming increasingly recognized as

important and necessary. Interpretation of theinformation is complex and requires a careful

consideration of all factors involved in assessing

the childs disease.


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` I s know risk factor for glaoucoma

` (Least than 555 micron)= thinner corneal (

Primary open angle gloucoma ) POAG

` Thickness of Corneal affect the tonometricreading.


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` Device used to measure the apparent thickness

of the cornea.

` Several Teachniques

` A. Optical` B. Ultrasonic principle


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` Figure 6-4. Pachymeter.A

pachymeter (Pocket Pachymeter,Quantel Medical, Bozeman, MT)

is an ultrasound device that mthe

easures cornea thickness by

determining the time it takes for asound wave to reflect off inner

surface of the cornea.

Measurements are taken by

placing an anesthetic drop on theeye and gently touching the probe

to the surface of the cornea.


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figure6-5. Pachymetry. Corneal thickness is measured by

administering an anesthetic drop to the eye and then

gently placing the pachymeter probe against the outersurface of the cornea.


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Chapter 5 Pa Chyme Try

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