Central corneal thickness and corneal hysteresis associated with glaucoma damage

PURPOSE: We sought to measure the impact of central corneal thickness (CCT), a possible risk factor for glaucoma damage, and corneal hysteresis, a proposed measure of corneal resistance to deformation, on various indicators of glaucoma damage. DESIGN: Observational study. METHODS: Adult patients of the Wilmer Glaucoma Service underwent measurement of hysteresis on the Reichert Ocular Response Analyzer and measurement of CCT by ultrasonic pachymetry. Two glaucoma specialists (H.A.Q., N.G.C.) reviewed the chart to determine highest known intraocular pressure (IOP), target IOP, diagnosis, years with glaucoma, cup-to,disk ratio (CDR), mean defect (MD), pattern standard deviation (PSD), glaucoma hemifield test (GHT), and presence or absence of visual field progression. RESULTS: Among 230 subjects, the mean age was 65 14 years, 127 (55%) were female, 161 (70%) were white, and 194 (85%) had a diagnosis of primary open-angle glaucoma (POAG) or suspected POAG. In multi-variate generalized estimating equation models, lower corneal hysteresis value (P = .03), but not CCT, was associated with visual field progression. When axial length was included in the model, hysteresis was not a significant risk factor (P = .09). A thinner CCT (P = .02), but not hysteresis, was associated with a higher CDR at the most recent examination. Neither CCT nor hysteresis was associated with MD, PSD, or GHT "outside normal limits." CONCLUSIONS: Thinner CCT was associated with the state of glaucoma damage as indicated by CDR. Axial length and corneal hysteresis were associated with progressive field worsening.