Corneal pachymetry

Corneal pachymetry is the process of measuring the thickness of the cornea. A pachymeter is a medical device used to measure the thickness of the eye's cornea. It is used to perform corneal pachymetry prior to refractive surgery, for screening, LRI surgery and is useful in screening for patients suspected of developing glaucoma among other uses.

It can be done using either ultrasonic or optical methods . The contact methods, such as ultrasound and optical such as confocal microscopy (CONFOSCAN), or noncontact methods such as optical biometry with a single Scheimpflug camera (such as SIRIUS or PENTACAM), or a Dual Scheimpflug camera (such as GALILEI), or Optical Coherence Tomography (OCT, such as Visante) and online Optical Coherence Pachymetry (OCP, such as ORBSCAN). Corneal Pachymetry is essential prior to a refractive surgery procedure for ensuring sufficient corneal thickness to prevent abnormal bulging of the cornea, a side effect known as ectasia.

The instrument used for this purpose is known as a pachymeter. Conventional pachymeters are devices that display the thickness of the cornea, usually in micrometres, when the ultrasonic transducer touches the cornea. Newer generations of ultrasonic pachymeters work by way of Corneal Waveform (CWF). Using this technology the user can capture an ultra-high definition echogram of the cornea, somewhat like a corneal A-scan. Pachymetry using the corneal waveform process allows the user to more accurately measure the corneal thickness, verify the reliability of the measurements that were obtained, superimpose corneal waveforms to monitor changes in a patient's cornea over time, and measure structures within the cornea such as micro bubbles created during femto-second laser flap cuts.

Corneal pachymetry is essential for other corneal surgeries such as Limbal Relaxing Incisions. LRI is used to reduce corneal astigmatism by placing a pair of incisions of a particular depth and arc length at a steep axis of corneal astigmatism. By using the corneal pachymetry the surgeon will reduce the chances of perforation of the eye and improves surgical outcome. Newer generations of pachymeters will help surgeons by providing graphical surgical plans to eliminate astigmatism.

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