Abstract
Abstract: :
Purpose: Recently, increasing attention has focused on corneal parameters, particularly central corneal thickness (CCT), as potential determinants of both measured IOP and glaucoma risk. We sought to measure the impact of CCT and corneal hysteresis (corneal resistance to deformation) on glaucoma progression and other disease outcomes. Methods: Persons over the age of 18 years presenting to the Glaucoma Service of the Wilmer Eye Institute underwent, in random order, measurement of IOP by Goldmann Applanation and Non–Contact Tonometry (NCT, Reichert Systems). NCT was used to calculate corneal hysteresis. CCT was measured by ultrasonic pachymetry, and the chart reviewed by a glaucoma specialist (HQ, NC) to determine: highest known IOP, target IOP, diagnosis, years with glaucoma, current cup–to–disc ratio (CDR), mean defect (MD) and glaucoma hemifield test (GHT) on the most recent reliable visual field, and presence or absence of visual field progression. Progression was defined according pre–determined criteria over at least three field tests. 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 OAG. In multivariate GEE models including data from both eyes, adjusting for age, race, gender, years since glaucoma diagnosis, highest known and current IOP and treatment, a lower hysteresis (p = 0.03), but not CCT, was associated with visual field progression. When axial length (p = 0.006) was included in the model, hysteresis was no longer significant (p = 0.13). A thinner CCT (p = 0.007), but not hysteresis, was associated with a higher CDR. Neither CCT nor hysteresis was predictive of a GHT "outside normal limits." Conclusions: Both thinner CCT and lower corneal hysteresis appear to be independently associated with glaucoma damage and progression. Axial length may be deserving of further attention as a biometric indicator of glaucoma risk.
Keywords: intraocular pressure • cornea: clinical science • optic disc