OPT is a new tonographic procedure permitting easy and reproducible examination of the regulative IOP behavior and the detection of impaired hydrodynamics as an early sign of glaucoma. OPT avoids errors associated with conventional tonographic procedures, takes measurements in IOP ranges where better separation between healthy and glaucoma eyes may be expected, performs simultaneous examination of both eyes, and permits IOP measurement by applanation tonometry in all phases of the examination process. OPT is easier to perform, is better tolerated by the patient and only takes half as long as conventional tonography. The effectiveness of the new procedure is demonstrated by the results of examinations of 253 eyes.