ROC analysis of Heidelberg Retina Tomograph optic disc shape measures in glaucoma.

ABSTRACT

OBJECTIVE: To determine the capacity of the Heidelberg Retina Tomograph (HRT) optic disc shape measures to detect glaucomatous damage. DESIGN: Prospective study. SETTING: Department of ophthalmology at a university-affiliated hospital in Vancouver. PATIENTS Ninety-seven consecutive patients from the glaucoma centre and 129 healthy subjects selected from volunteers and employees of the department. One eye of each subject was chosen randomly. OUTCOME MEASURES: Visual fields, as assessed with the Humphrey perimeter, program 30-2, and 12 HRT shape characteristics disc area, cup area cup/disc area ratio, rim area, cup volume, rim volume, mean cup depth, maximum cup depth, cup shape measure, height variation contour, mean retinal nerve fibre layer thickness and retinal nerve fiber layer cross-section area. ROC (receiver operating characteristic) curves were used to analyse the capacity of each HRT characteristic to detect glaucoma. RESULTS: Statistically significant difference were found between the control and glaucoma groups in age, cup area, cup/disc ratio, rim area, cup volume, rim volume, mean cup depth, cup shape measure, mean retinal nerve fibre layer thickness and retinal nerve fibre layer cross-section area (p < or = 0.003, t-test). The largest (i.e., best) ROC curve area was found for cup shape measure (area = 0.812), rim area (0.809), cup/disc area ratio (0.804) and rim volume (0.768). The mean reference height was 0.31 mm (standard deviation [SD] 0.14 mm) for the control group and 0.29 mm (SD 0.12 mm) for the glaucoma group, a nonsignificant difference. CONCLUSIONS: Cup shape measure was the most predictive HRT shape characteristic.