Intraocular pressure adjusted for central corneal thickness as a screening tool for open-angle glaucoma in an at-risk population

Abstract

Objective: Evaluation of intraocular pressure (IOP) adjusted for central corneal thickness (CCT) screening for open-angle glaucoma (OAG) in an at-risk population. Study Design: Community-based screening clinic. Participants: Three hundred and forty-nine persons of black race, or >50 years of age, or with a positive family history of glaucoma. Methods: Ophthalmological examination including Goldmann applanation tonometry, ultrasonographic corneal pa-chymetry, and visual field testing. Glaucomatous optic nerve damage with visual field loss was the gold standard. IOP was adjusted for CCT based on 3 nomograms. Results were compared with screening using unadjusted IOP. Outcome measures included sensitivity, specificity, areas under the receiver operating characteristic (ROC) curves, positive and negative predictive values (PPVs and NPVs), as well as positive and negative likelihood ratios. Results: No significant difference in CCT was found between those with glaucoma (560 [SD 37] µm, n = 31) and those without (557 [SD 35] um, n = 233). Screening adjusted IOPs for glaucoma with an IOP > 21 mm Hg resulted in PPVs of 23.8% to 25% and NPVs of 89.3% to 89.6%, similar to preadjustment values. Areas under the ROC curves varied from 0.544 to 0.571 post adjustment from the initial value of 0.574. Conclusions: IOP adjusted for CCT is unlikely to improve tonometry as a screening tool for OAG in an at-risk population.