Introduction:
The cornea is the transparent portion of the eye that covers the iris and pupil. The cornea benefits the eye in two ways; it aids in protecting the eyes from contaminants like dust and bacteria. The cornea performs this protective function with the help of eyelids, the eye socket, tears, and the sclera, the white component of the eye. The cornea serves as the outermost part of the lens. Like a window, it directs and concentrates the light that enters the eye. Between 65 to 75 percent of the eye's overall focusing capability comes from the cornea. The average central corneal thickness can range from 535 microns to 550 microns.
What Is Corneal Pachymetry Test?
Corneal pachymetry is a diagnostic test used to measure the thickness of the cornea, which is the clear front part of the eye. This test is performed by using a specialized instrument called a pachymeter, which uses ultrasound waves to measure the thickness of the cornea.
The corneal pachymetry test is important in the diagnosis and management of various eye conditions, such as glaucoma, keratoconus, and corneal dystrophies. Pachymetry is an essential indicator of overall corneal health. In pachymetry, corneal thickness is measured in micrometers.
What Diseases Can be Diagnosed Using Pachymetry?
The various diseases that can be diagnosed in corneal pachymetry tests include:
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Patients With Glaucoma - Pachymetry is very important in treating glaucoma. Eye pressure (intraocular pressure) can increase as a result of the condition of glaucoma. Increased eye pressure can lead to retinal nerve fiber loss, impaired vision, or blindness. Corneal pachymetry is an essential component of glaucoma testing due to the ocular hypertensive treatment study (OHTS) discovery that central corneal thickness is a reliable indication of glaucoma risk.
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Patients For Refractive Surgery - Refractive surgery is correcting refractive defects such as myopia. In refractive surgical techniques like laser treatments (LASIK), the thickness of the cornea is essential. To decide if a person is a candidate for laser vision correction, it is essential to recognize corneal thickness. It is crucial to understand how much tissue will be removed because a portion of the treatment involves removing tissue that would. Although it does not lead to issues or disease, doing a refractive treatment on someone with an extremely thin cornea could result in severe vision loss. The cornea of specific individuals may be thinner than average.
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To Monitor the Development Of Corneal Disorders - The pachymetry test is beneficial to monitor the development of corneal diseases like keratoconus, corneal edema, and dystrophies.
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To Plan and Monitor Corneal Surgery (Corneal Transplantation) - Eye doctors use pachymetry to evaluate donor corneas for transplantation and the success of such procedures.
What Are the Different Techniques that Can be Used in a Pachymetry Test?
Pachymetry can mainly be carried out using two techniques,ultrasonic method, and optic method.
1. Ultrasonic Method -
This technique is the most popular and is considered the gold standard. Henderson and Kremer introduced the ultrasonic pachymeter in 1980. As the name suggests, ultrasound pachymetry uses ultrasound principles to assess the cornea's thickness. Portable, affordable equipment is used in this procedure. The probe that touches the cornea to measure corneal thickness by ultrasound must be positioned correctly, which is its most significant disadvantage. The reading could be inaccurate if there is even a slight displacement. Some ultrasound pachymeters have built-in risk factor calculators and are more suited to glaucoma testing.
2. Optical Method -
Optical pachymeters vary in their designs. Some optical pachymeters can be put on the slit lamp, a biomicroscope used by eye care professionals. Specular microscopy can be used by other apparatus to measure pachymetry. However, this device does not directly touch the cornea. Optical coherence tomography (OCT) pachymetry is one kind of optical pachymetry that has grown in popularity. This pachymetry also takes measurements without touching the cornea. One disadvantage of optical pachymetry is that insurance companies typically cover ultrasound pachymetry but not always optical pachymetry; therefore, it is likely that healthcare professionals will request payment.
Other alternative methods are:
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Pachycam.
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Pentacam.
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Ocular response analyzer.
How Is Pachymetry Test Performed?
The pachymetry ultrasound examination requires the patient to sit on a stool or chair for the examination. To measure corneal thickness, the doctor injects an anesthetic solution into the eye and places a probe on the corneal surface. The measurement can be repeated if more than one location on the corneal surface is required. When the examination starts, the patient's eyes continuously focus on a light source for a few seconds while the device scans the cornea in a sequence of motions. A specialized computer carries out the morphological and morphometric analysis, extracts the value of the pachymetry recorded at various spots on the corneal surface, and determines the minimal value of corneal thickness.
Is the Corneal Pachymetry Test Painful?
No, it is not a painful procedure. No discomfort is involved when doing an ultrasonic pachymetry examination after anesthesia has been administered to the eye. Using a little probe to touch the corneal surface requires an anesthetic to prevent pain or discomfort. Since there is no touch with the corneal surface during the pachymetry visual examination.
Conclusion:
The corneal pachymeter is a simple, painless test used to assess the thickness of the cornea. A pachymeter is a specialized hand-held equipment that an eye specialist uses to do pachymetry. The pachymeter measures the thickness of the translucent tissue covering the front of the eye as soon as the eye care expert contacts the instrument's tip to the cornea. Pachymetry examinations are used by eye specialists for a variety of reasons, in addition to assessing glaucoma risk in patients. For example, before refractive eye surgery, in which a doctor removes a small layer of the cornea to enhance the patient's visual acuity, the painless test helps assess the thickness of a patient's cornea. In addition, eye doctors use pachymetry to evaluate donor corneas for transplantation and the success of such procedures. There are two primary categories of pachymetry: ultrasound, which generates images using sound waves, and optical pachymeters, which employ microscopes.
