Procedure that determines the thickness of the cornea.

Why the test is performed:

This test measures the thickness of the cornea, by means of ultrasound, when the ultrasonic transducer touches the cornea.
It is of great importance when it comes to measuring the amount of refractive error, given that a low level of corneal thickness limits the amount of refractive error to be treated.
Some patients shouldn’t be operated on with a certain technique since their corneal thickness is not enough to keep a stable and secure medium term result.
Also, this test is requested to have a broader perspective into intraocular pressure (IOP), as it is an important factor when it comes to overestimating or underestimating the intraocular pressure.

How it is performed:

The ultrasonic wave is reflected by the rear face of the cornea (like an echo) before returning to the ultrasonic transducer, which in turn turns the wave into electricity, to be returned to the microprocessor, which estimates the time it took the wave to travel from its emission to its return. The measured time is then processed into distance, which determines the thickness of the cornea (in microns, 1cm = 100 microns).

How to prepare for the test:

The patient cannot be wearing (and must remove) his or her contact lenses before the exam.