Flash and pattern electroretinograms during and after acute intraocular pressure elevation in cats

Area of Science:

• Ophthalmology
• Neuroscience
• Physiology

Background:

• Intraocular pressure (IOP) elevation can affect retinal function.
• Systemic blood pressure (BP) also plays a role in retinal health.
• Understanding the interplay between IOP, BP, and retinal function is crucial for diagnosing and treating eye conditions.

Purpose of the Study:

• To evaluate retinal functionality under conditions of elevated IOP and varying systemic BP.
• To determine the critical perfusion pressure threshold for retinal electrical activity.
• To investigate the recovery patterns of different retinal responses after reduced perfusion.

Main Methods:

• Electroretinogram (ERG) recordings were used, including flicker ERG (FERG) and pattern ERG (PERG).
• Cats were used as the animal model.
• Mean arterial blood pressure (BPm) was pharmacologically manipulated, and a range of IOP values were tested.

Main Results:

• Both FERG and PERG responses were impaired when eye perfusion pressure (PP = BPm - IOP) decreased.
• Retinal electrical activity disappeared at a critical PP of approximately 20 mm Hg, independent of absolute IOP.
• PERG recovery was delayed compared to FERG recovery after prolonged critical perfusion pressure, indicating differential vulnerability.

Conclusions:

• Reduced eye perfusion pressure, driven by vascular factors, is a primary cause of retinal electrical activity loss during short-term IOP elevation.
• Retinal ganglion cells, likely the source of PERG, exhibit delayed recovery from acute ischemic episodes.
• These findings highlight the importance of maintaining adequate retinal blood supply for preserving visual function.