Computer ultrasonic pachymetry
Corneal Pachymetry
(This test is part of the initial diagnostic evaluation.)
Corneal pachymetry is a method used to measure the thickness of the cornea.
The measurement can be done:
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with contact, using ultrasound;
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or without contact, using optical biometry or optical coherence tomography (OCT).
Normally, corneal thickness is between 410 and 625 µm, with an average of about 515 µm.
Measuring corneal thickness is very important when planning laser vision correction.
For pachymetry, a device called a pachymeter is used.
Standard pachymeters are devices with an ultrasound probe and show corneal thickness usually in micrometres.
Contact pachymetry means the tip of the device touches the cornea, so numbing eye drops are needed.
The accuracy of these measurements depends on:
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how perpendicular the probe is to the corneal surface;
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and how precisely the ultrasound sensor is positioned.
In our clinic, we use more modern devices that scan the cornea with a laser without touching it, which makes the test very comfortable and highly accurate.
Pachymetry is also considered an important test in the early diagnosis of glaucoma.
Studies have shown that changes in corneal thickness can be a reliable sign of glaucoma developing, especially when evaluated together with standard intraocular pressure measurements.
The latest generations of tonometers combine the functions of a tonometer (measuring eye pressure) and a pachymeter, allowing more accurate eye pressure readings by taking corneal thickness into account.
