Abstract
Abstract: :
Purpose: To test our hypothesis that an eye with more advanced glaucomatous cupping has a decreased central corneal thickness (CCT) measurement compared to its fellow eye with less cupping. Methods: Subjects, who had asymmetric glaucoma defined as cup to disc ratio (CDR) asymmetry greater than 0.2, were recruited under a protocol approved by the UM IRBMED. A priori power calculations were performed to determine the number of subjects needed to show an intereye difference of 10 microns. The CDR was evaluated by two glaucoma specialists in a masked fashion based on stereo disc photos. If there was no consensus between the two evaluators, a third glaucoma specialist was used as an arbitrator. Exclusion criteria were any corneal pathology associated with clinically significant corneal edema, prior refractive surgery, intraocular surgery in the past six months, and any other optic neuropathy aside from glaucoma. The CCT was measured by ultrasonic pachymetry (Pachette, DGH Technology, Inc., Exton, PA) in a standardized fashion by averaging five consecutive readings on the central cornea. A paired Student’s t–test was used to compare the average CCT measurements between eyes. Results: A total of 41 enrolled subjects met inclusion criteria. The mean difference in CCT between the eye with a larger CDR and the fellow eye with a smaller CDR was –13.29 microns + 21.53 (standard deviation), which was significant (P=0.0002, paired t–test). The eye with the larger CDR had the thinner cornea in 34 out of the 41 pairs of eyes (83%; P<0.01, sign test). Conclusions: There is a statistically significant association between a thinner central cornea in eyes with more glaucomatous cupping compared to their fellow eye with less cupping. Our findings of asymmetric CCT measurements in patients with asymmetric CDR raise the question of whether the cornea is a biological indicator of glaucoma in some susceptible eyes.
Keywords: optic disc • cornea: clinical science • imaging/image analysis: clinical