How do doctors determine corneal thickness when you decide to undergo the lasik surgery?

Several ways: There are a number of ways to measure corneal thickness. Ultrsound is the most common way. Also, there are a number of optical ways to determine corneal thickness using different forms of topography or optical coherence tomography (oct).

Careful measurement: There are 2 major ways to measure corneal thickness: ultrasound, which works similarly to what is used to "look" at a developing fetus; and optical coherence tomography (oct), which uses light rays to do the same thing. Neither is painful (in fact, you cannot feel it being done).

Ultrasound: There are many methods to check corneal thickness. Ultrasound and corneal imaging are very common, and quickly done in the office routinely.

Pachymeter: Corneal thickness is measured using an ultrasonic pachymeter. It is painless and takes only a few seconds.