If IOP increases, what happens to the Ocular perfusion pressure?

Ocular perfusion pressure (OPP) is a critical factor in maintaining the health of the optic nerve and perfusion to the eye. It is calculated as the difference between the mean arterial pressure (MAP) and intraocular pressure (IOP): OPP = MAP - IOP.

When IOP increases, the OPP decreases because the IOP component of the equation becomes larger while the MAP remains relatively constant. This decrease in OPP can lead to reduced blood flow to the optic nerve head, which may have implications for conditions such as glaucoma, where increased IOP is a significant risk factor for optic nerve damage.

The other options do not accurately reflect the relationship between IOP and OPP. For example, an increase in OPP would imply that the eye is being better perfused despite rising IOP, which contradicts the physiological relationship established above. Hence, the decrease in OPP with an increase in IOP is critical to understanding the impacts on ocular health and is a key point for those studying ocular physiology.