A pachymeter is a medical device

Medical device

A medical device is a product which is used for medical purposes in patients, in diagnosis, therapy or surgery . Whereas medicinal products achieve their principal action by pharmacological, metabolic or immunological means. Medical devices act by other means like physical, mechanical, thermal,...

 used to measure the thickness of the eye

Human eye

The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

's cornea

Cornea

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...

. It is used to perform Corneal pachymetry

Corneal pachymetry

Corneal pachymetry is the process of measuring the thickness of the cornea using contact methods, such as ultrasound and confocal microscopy , or noncontact methods such as optical biometry with a single Scheimpflug camera , or a Dual Scheimpflug camera , or Optical Coherence Tomography and online...

 prior to LASIK

LASIK

LASIK or Lasik , commonly referred to simply as laser eye surgery, is a type of refractive surgery for correcting myopia, hyperopia, and astigmatism...

 surgery, for Keratoconus

Keratoconus

Keratoconus , is a degenerative disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual curve....

 screening, LRI surgery and is useful in screening for patients suspected of developing glaucoma

Glaucoma

Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...

 among other uses.
Modern devices use ultrasound technology , while earlier models were based on optical principles. The ultrasonic Pachymeters traditionally have been devices that provide the thickness of the human cornea in the form of a number in micrometres that is displayed to the user. The newer generation of ultrasonic pachymeters. work by way of Corneal Waveform (CWF). Using this technology the user can capture an ultra high definition echogram of cornea, think of it as a corneal A-scan. Pachymetry using the corneal waveform allows the user to more accurately measure the corneal thickness, have to ability to check the reliability of the measurements that were obtained, have the ability to superimpose corneal waveform to monitor the change of patients cornea over time, and ability to measure structures within the cornea such as micro bubbles created in the cornea during femto-second laser flap cut.