At one time, corneal thickness was thought to be about the same in all patients. Recent research, however, suggests that corneal thickness can vary quite dramatically from person to person.
Pressure inside the eye is measured by a device called a "tonometer." The accuracy of the pressure reading, however, may be misleading. Studies have shown that a thinner cornea may result in an artificially low-pressure measurement, while a thicker cornea may result in a measurement that is higher. This possible misreading is important, because a person with a seemingly low pressure (suggesting he has little risk of developing glaucoma) may actually be at high risk and in need of treatment. The person's true eye pressure only appears to be lower due to the thinness of the cornea.
Doctors now include the measurement of the thickness of the cornea, known as pachymetry, as a part of standard glaucoma evaluations. Although researchers disagree on the exact correction factor that should be used, doctors now have a general idea of what assumptions to make if a patient has a somewhat thin or thick cornea. Pachymetry has become a standard diagnostic test in the diagnosis of glaucoma.
Source:
Ophthalmic News and Education Network, "Normal Tension Glaucoma: Corneal Pachymetry." American Academy of Ophthalmology (online course) May 2006.
