Blood pressure modifies retinal susceptibility to intraocular pressure elevation

Area of Science:

• Ophthalmology
• Neuroscience
• Physiology

Background:

• Primary open-angle glaucoma affects over 67 million people globally.
• Elevated intraocular pressure (IOP) is a key risk factor for glaucoma.
• Ocular perfusion pressure (OPP), influenced by arterial blood pressure and IOP, is critical for retinal health but its precise role is unclear.

Purpose of the Study:

• To investigate how acute changes in mean arterial pressure (MAP) affect retinal neuronal function and blood flow under elevated IOP.
• To determine the susceptibility of retinal function to IOP challenges at different MAP levels.

Main Methods:

• Rats were subjected to low, moderate, or high MAP levels using pharmacological agents.
• Intraocular pressure (IOP) was progressively increased while measuring retinal function via electroretinograms (b-wave and STR).
• Ocular blood flow was assessed using laser-Doppler flowmetry.

Main Results:

• Both bipolar cell (b-wave) and inner retinal function (STR) decreased with increasing IOP.
• Retinal function was more resilient to IOP challenges at high MAP and more susceptible at low MAP.
• Higher IOP levels were required to reduce ocular blood flow in animals with higher MAP.

Conclusions:

• Acute elevation of arterial blood pressure can ameliorate, while acute hypotension can exacerbate, the susceptibility of retinal function to IOP challenges.
• These findings suggest that arterial blood pressure modulation plays a significant role in protecting retinal function during IOP fluctuations.
• Modifications in ocular blood flow appear to be a key mechanism mediating these effects.