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Understanding the Pachymetry Test for Corneal Thickness

Pachymetry is a painless, simple test that quickly measures the thickness of the cornea.

A medical device called a Pachymeter is used to measure the thickness of the eye's cornea. It is used to perform corneal pachymetry before refractive laser eye surgery, for Keratoconus screening, Cataract, and LRI surgery, and is useful in screening for patients suspected of developing glaucoma among other uses.


Corneal thickness as measured by pachymetry is vital in the eye care field for several reasons. Pachymetry can be performed by two methods which are - ultrasound techniques and by optical techniques.


Ultrasound Pachymetry


As the name implies, Ultrasound pachymetry uses ultrasound principles to measure the thickness of the cornea. This method uses devices that are portable and cost-effective.


The biggest drawback of measuring corneal thickness by ultrasound is that the probe used to touch the cornea has to be positioned perfectly. Any minor movement and the result may be inaccurate. Some ultrasound pachymetry is designed more for glaucoma testing and includes built-in risk factor calculators.


Optical Pachymetry


Optical pachymetry varies on the design. Some optical pachymetry is designed to be mounted onto a biomicroscope that eye healthcare providers use called the slit lamp.


Other devices can measure pachymetry using specular microscopy. This gadget has no direct contact with the cornea. OCT, or optical coherence tomography pachymetry, is a prominent kind of optical pachymetry. OCT pachymetry likewise does not require any contact with the cornea to get readings. With the help of Pachymetry, healthcare providers understand if the cornea is swollen.


Fuch's Dystrophy, for example, can produce an increase in fluid in the cornea, resulting in an increase in total thickness. Even wearing contact lenses might cause substantial corneal edema at times. Under the microscope, this may be difficult to see. Pachymetry, on the other hand, will reveal a distinct increase in thickness.


In refractive surgical procedures such as Laser eye surgery in Delhi, corneal thickness is extremely important. Because part of the treatment involves eliminating tissue that will leave the corneal thinner, knowing exactly how much will remain is critical in determining if a person is a suitable candidate for laser vision correction.


Some people may have a cornea that is significantly thinner than usual. Although, it does not create difficulties or illness, however, if a laser eye surgery is performed on someone for corrective refractive disorders whose cornea is exceedingly thin, it might result in severe vision loss.


A Guide to understanding Pachymetry in Glaucoma Care


Pachymetry is also useful in the treatment of glaucoma. Glaucoma is a condition in which the eye pressure rises. This increased eye pressure can induce nerve fiber loss in the retina, resulting in impaired vision or blindness.


Most approaches include measuring ocular pressure with a tool that is in direct contact with the cornea. Researchers revealed that corneal thickness varies somewhat throughout the population.


Corneal thickness can affect ocular pressure measurement. Furthermore, the Ocular Hypertensive Treatment Study (OHTS) identified central corneal thickness as an independent indication of glaucoma risk, making corneal pachymetry an important aspect of glaucoma testing.


Corneal pachymetry is important for other corneal surgeries such as Limbal Relaxing Incisions. LRI reduces corneal astigmatism by making a pair of incisions of a certain depth and arc length at a steep axis of corneal astigmatism.


By using corneal pachymetry the surgeon will reduce the chances of perforation of the eye and improve surgical outcome. Newer generations of pachymetry will help surgeons by providing graphical surgical plans to eliminate astigmatism. Before cataract surgery, it is also essential to measure pachymetry to detect a condition known as Fuch’s Corneal Endothelial Dystrophy.


In this condition, the cornea is thickened due to swelling because it is unable to pump out enough water. This is because there has been a loss of endothelial cells lining the cornea's internal back surface. Cataract surgery may cause further damage to the cornea, potentially resulting in vision loss in such people.


Modern devices use ultrasound technology, but earlier models were completely based on optical principles. Traditionally, ultrasonic Pachymeters were devices that provided the thickness of the human cornea in the form of a number in micrometers that was shown to the user.


The newer generation of ultrasonic pachymetry works by way of Corneal Waveform (CWF). Using this technology, the user can capture an ultra-high-definition echogram of the cornea, and think of it as a corneal A-scan.


Pachymetry using the corneal waveform allows the user to more accurately measure the corneal thickness, can check the reliability of the measurements that were obtained, can superimpose the corneal waveform to monitor the change of patients cornea over time, and ability to measure structures within the cornea such as microbubbles created in the cornea during femtosecond laser flap cut.


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