The Heidelberg Retina Tomograph (HRT) is a proven, essential tool for detecting and managing glaucoma, especially for assisting in the identification of pre-perimetric disease and tracking progression. The Ancillary Study to the Ocular Hypertension Treatment Study (OHTS) demonstrated that optic disc analysis detected glaucoma conversion in 55% of cases, before any detectable loss of visual function. The HRT has proved to be a robust predictor of glaucoma. OHTS also concluded that the HRT recognized temporal superior defects which later developed into confirmed glaucoma in 40% of cases – looking only at baseline measurements – then confirmed the diagnosis with an average of 5 years of follow-up. Equally impressive was that 93% of all HRT cases flagged as within normal limits at baseline remained within normal limits during the same time period.