Role of corneal thickness in glaucoma incidence and progression becoming clearer

CORNEAL thickness may not only affect IOP measurements performed with Goldmann applanation tonometry (GAT) but may also be linked to the aetiology of glaucoma itself. However, there is no practical or reliable means at present to adjust IOP measurements in individual patients for variations in corneal thickness, James Brandt MD, professor of ophthalmology and director, glaucoma service, University of California, Davis, US told the 6th International Glaucoma Symposium. While raised IOP is the principal risk factor for glaucoma and glaucoma progression, it is well established that differences in corneal thickness can lead to the overor underestimation of IOP as measured by GAT, he noted. For example, when patients have their corneas thinned by corneal refractive surgery, their IOP, as measured by GAT, becomes lower, although there is no change in the inflow and outflow of aqueous humour in the eye, he said. “We owe a great deal of debt to Hans Goldmann for bringing a modern reproducible mechanism into tonometry within the workflow of an eye clinic. But Prof Goldmann recognised that corneal thickness would play a role in this device and during the 60s, 70s and 80s it was recognised that, because of variations in corneal thickness, Goldmann tonometry overor underestimated the true IOP by a significant amount,” he added.