Evaluation of a Novel Method for Increasing Intraocular Pressure in Healthy Subjects

Adequate perfusion is necessary for maintaining tissue function. This applies also for the eye, in which ocular perfusion pressure (OPP) is generally estimated as the difference between mean arterial pressure (MAP) and intraocular pressure (IOP). In the latter formula, IOP substitutes for central retinal venous pressure (CRVP), which is assumed to be slightly higher than IOP to allow blood flow to exit the eye. It has, however, been found that in some patients CRVP is elevated and significantly higher than IOP, which would lead to a decrease in OPP which is not taken in account with the proposed formula. Therefore, techniques for measurement of CRVP are warranted. Recently, a new, method for measurement of this parameter without corneal contact has been introduced. Briefly, with this method, IOP is elevated until the vein collapses, which then equals CRVP. In the present study this technique will be applied in 12 healthy subjects to validate whether the values that are preset by the device correlate to measurements obtained with standard Goldmann applanation tonometry. For this purpose, IOP will be experimentally increased in steps of approximately 5mmHg until it reaches 40mmHg as measured by applanation tonometry. After a resting period of 30 minutes, IOP will be again increased stepwise to 40 mmHg while retinal vessel diameters will be monitored using dynamic vessel analyzer. During this session CRVP will be measured. After another resting period of 30 minutes IOP will be stepwise increased a third time and after each step OCT, OCT-A and OCT EDI will be performed.