Page 43 - The UK Guide to Laser Eye Surgery
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Questions about technology
43
 Pachymetry
What actually happens?
There are three main types of pachymetry:
Hand-held ultrasound probes:
A topical anaesthetic drop is placed in each eye to numb the surface of the eye for approximately 15 minutes. The optometrist then sits or stands in front of you and gently holds open your eyelid. They will then gently touch a hand-held probe onto the surface of the eye to take readings of the thickness of the cornea.
Very high-frequency ultrasound
3D scanning:
In VHF ultrasound, you have your eyes numbed with anaesthetic drops, and have your eye positioned over a watertight rubber eyepiece. The eyepiece is then filled with warm saline solution (like artificial tears). Several arc-scans of the entire cornea are made to generate the thickness profile of each individual layer within
the cornea. This scan can also be used to measure the thickness of the corneal flap following LASIK.
Optical pachymetry devices:
You rest your chin on a padded support and stare straight into the examining instrument. The clinician sits in front of you and aligns the instrument by having you focus on a visual target. They will ask you to open your eyes widely to take a number of multi-coloured pictures that are printed and added to your medical record. The pictures are like maps, where the different colours show the thickness profile of your cornea.
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