Corneal Pachymetry – This is a measurement of the corneal thickness. The average cornea measures 555 – 588 microns. This measurement is taken with an ultrasonic device that causes no sensation or discomfort.

During the Summer of 2002, the results of a 5-year study on glaucoma in the Baltimore area was released – The Ocular Hypertension Treatment Study (OHTS), and it showed several important findings. It showed that the pressure we measure in someone’s eye is dependent on the thickness of their cornea (the clear window in the front of the eye). People with thin corneas tend to give falsely low pressure readings when we test them, and thus, we get a false impression that they are normal, when in fact they may not be.

People with thick corneas tend to give falsely higher pressures when tested, and thus are often started on treatment earlier because someone gets nervous about the elevated pressure and treats it like glaucoma. Thus, those with lower than normal thicknesses had a higher incidence of glaucoma progression and those with thicker corneas had a lower incidence of glaucoma progression.

Since we have initiated measuring the corneal thickness on all of our glaucoma patients, we have found some patients with thick corneas (greater than 588 microns) who have been able to reduce or eliminate their medications. We have also found patients with markedly thinned corneas that have required more aggressive treatment. This experience is being witnessed in ophthalmology offices around the world since the results of the OHTS study have been published, Summer 2002.