What is it?
What exactly is the examination of corneal pachymetry?
The pachymetry (pachymetry) of the cornea is a special examination which measures the thickness of the cornea. The importance of pachymetry is particularly important and necessary in both the estimation of glaucoma and in the preoperative examination of patients who are undergoing refractive surgery with excimer laser.
The ultrasonic pachymetry is performed using a “pen” which contacts the surface of the cornea and requires local anesthesia with drops. The test takes just a few seconds and is completely painless.
Pachymetry and glaucoma
The importance of pachymetry in glaucoma:
Glaucoma (glaucoma) is a common eye disease affecting millions of people. It is characterized as an insidious and irreversible eye condition that can even lead to complete blindness, if not treated early. Glaucoma is usually due to high fluid pressure inside the eye. This pressure is called intraocular pressure, increases the risk of progressive destruction of the optic nerve leading to vision loss. Glaucoma develops slowly over a period of years. It is a “silent” disease, since most patients, in the early stages, often do not show symptoms. Increased intraocular pressure (typically over 20-22 mmHg) is the first indication of the existence of the disease, although there are rare cases where we have glaucoma even with normal pressure (low pressure glaucoma – here, the vascular factor plays an important role).
Several studies have shown that the central thickness of the cornea is an important indicator for the development of glaucoma. Eyes with a thickness of 550 microns or less are three times more likely to develop glaucoma, from eyes with a cornea thickness greater than 590 microns. For many ophthalmologists, the combination of elevated intraocular pressure (greater than 24mmHg) and thin cornea (thinner than 550 microns) can be the basis for antiglaucomatous treatment aimed at a possible development of glaucoma in the future.
Pachymetry and refractive surgery
The importance of pachymetry on refractive surgery with laser:
The corneal pachymetry is a necessary examination for preoperative control of a patient that will undergo refractive surgery with excimer laser. The result of pachymetry, coupled with the degree of the optical error to be corrected, is that which will substantially determine the final selection of the refractive technique that will be followed during the operation. The remaining corneal stroma (residual stroma) is an important parameter for all refractive surgeons.
If the thickness is not sufficient, usually, selecting the methods of conventional LASIK and Z-LASIK (PRK is applied). Finally, pachymetry, as an element is useful in the thick flap decision (corneal flap thickness).