Abstract
Abstract: :
Purpose:To evaluate the clinical ability of HRT total cup volume in detecting glaucomatous visual field defects in a large clinical setting Methods:301 patients (135 normal, 109 with OHT, 57 with POAG) were enrolled. Normal individuals (mean age 56±11 yrs) had a normal 24/II HFA visual field (VF), IOP = 22 mmHg on repeated measurements and normal VF. POAG patients (mean age 68±12 yrs) had abnormal VF (GHT "outside normal limits" and CPSD ≷ 4dB) and IOP ≷= 22 mmHg. HRT examination was performed with a 10° angle view. For study purposes a mean image of three repeated images was analyzed with the version 2.01 software. The contour line was manually traced by two of the Authors whose reproducibility has been previously tested. Standard HRT parameters have been collected. TCV has been calculated as follows: (Cup volume + (Mean RNFL thickness x Disc area) - Rim volume). TCV was calculated for the whole disc and for eight 45° disc sectors. One eye per patient was used for study purposes. The normative database reference population was established using the upper 95% prediction band of the regression of TCV on disc area in the normal group. Sensitivity and specificity were calculated by means of standard procedures. Results:At a specificity level of 97% (as determined by the regression analysis) sensitivity of TCV in detecting glaucomatous VF defects was 81%. In the OHT population TCV identified as abnormal 32 out of 109 patients. Pooling the normal and the OHT subjects in the "normal group", sensitivity and specificity resulted 81% and 86%, respectively. Conclusion:TCV is calculated on the basis of standard HRT parameters. It provides global or sectorial information on the morphology of the disc independent of the reference plane, and allows to well discriminate between normal and POAG patients. Our figures are similar to those provided by Wollstein (1998) using the Moorfields Regression Analysis.
Keywords: 498 optic disc • 430 imaging/image analysis: clinical • 356 clinical (human) or epidemiologic studies: systems/equipment/techniques