Glaucoma risk factors: The cornea

It has long been accepted that elevated intraocular pressure (IOP) is a key parameter in the diagnosis of glaucoma. IOP is used in the assessment of disease progression and response to treatment. In fact, it is the only modifiable risk factor for glaucoma. Therefore, its accurate measurement is critical. For over half a century, Goldmann applanation tonometry (GAT) has been the most widely used method of measuring IOP. In their seminal article, Goldmann and Schmidt determined that, in accordance with the Imbert-Fick Law, IOP is equal to the force necessary to flatten a spherical surface, divided by the surface area of that flattened surface (the cornea). GAT utilizes a cone that applanates a circular area of the corneal surface with a diameter of 3.06 mm. With this circular applanation area, the force necessary to overcome the resistance of the cornea to flattening is equal to the surface tension of the tear film. This allows the force applied to equal the IOP. © 2010 Springer-Verlag New York.

Duke Scholars

Author Leon Walker Herndon Jr. Ophthalmology, Glaucoma