Photopic electroretinographic sub-components reveal inner retinal function in a rat glaucoma model

Abstract

Purpose : Glaucoma is an irreversible and progressive optic nerve neuropathy that results in the death of retinal ganglion cells. In order to effectively assess the progression of inner retinal dysfunction in a rat glaucoma model, we conducted electroretinography under various stimulation conditions and analyzed photopic sub-components, namely the photopic negative response and oscillatory potentials, during different conditioning flashes.

Methods : Three episcleral veins in the right eyes of Sprague-Dawley rats were cauterized to induce an experimental model of glaucoma. Electroretinography (ERG) responses were measured before surgery and at 1, 2, 4, and 8 weeks after cauterization. Under the brief scotopic and photopic conditions, full-field ERG recordings were performed to evaluate the progression of glaucoma. In addition, two photopic parameters, the photopic negative response (PhNR) and oscillatory potentials (OPs), by employing prolonged conditioning flashes with various monochromatic background and test stimuli in rat eyes, were employed.

Results : Under brief flash conditions, we confirmed that the amplitude of the photopic b-wave was more greatly reduced over time than the amplitudes of scotopic a- and b-waves in glaucomatous eyes. Additionally, extensive photopic conditions with a longer duration and different monochromatic combinations made differences between the groups more noticeable. Especially in control animals, a conditioning flash of blue stimulation on a green background produced the largest b-wave and photopic negative response amplitudes and caused more pronounced oscillatory potential wavelets (oscillatory potential individual components). In glaucomatous eyes, a conditioning flash of blue stimulation on a green background significantly reduced photopic negative response amplitudes and abolished the robust oscillatory potential components.

Conclusions : These findings demonstrate that both photopic electroretinography sub-components, the photopic negative response and oscillatory potentials, can be used to assess the progression of inner retinal dysfunction in a rat glaucoma model.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Representative traces of each prolonged photopic ERG from a normal rat eye are shown for different color combinations.