Electroretinographic abnormalities in a rat glaucoma model with chronic elevated intraocular pressure

Area of Science:

• Ophthalmology
• Neuroscience
• Physiology

Background:

• Glaucoma is a progressive optic neuropathy characterized by retinal ganglion cell loss.
• Monitoring disease progression is crucial for effective treatment strategies.
• Electroretinography (ERG) is a functional test assessing the retina's electrical response.

Purpose of the Study:

• To evaluate the utility of electroretinographic (ERG) measurements in documenting retinopathy progression in a rat model of glaucoma.
• To identify specific ERG parameters that can serve as reliable biomarkers for glaucoma progression.

Main Methods:

• A rat model of chronic intraocular pressure (IOP) elevation was established via episcleral vein cautery.
• Sequential electroretinograms (ERG) were recorded in glaucomatous and control eyes over periods up to 25 weeks.
• Scotopic and photopic ERG parameters, including a-wave, b-wave, and oscillatory potential (OP) amplitudes and implicit times, were analyzed.

Main Results:

• Significant time-dependent changes in ERG parameters were observed in glaucomatous eyes compared to contralateral normal eyes.
• Oscillatory potentials (OPs) demonstrated the earliest significant alterations, appearing within 3 weeks of elevated IOP.
• OPs showed sustained decline over 25 weeks (approx. 1.5% per week) and effectively discriminated between glaucomatous and normal eyes, especially beyond 8 weeks.

Conclusions:

• Electroretinography (ERG), particularly scotopic oscillatory potentials (OPs), is a valuable tool for monitoring glaucoma progression in this rat model.
• OPs provide a sensitive and reliable measure of retinal pathophysiology in response to elevated IOP.
• ERG measurements can document functional changes associated with glaucoma progression over extended periods.