Abstract
Methods: :
For MFERG analysis, contact lens electrodes and stimuli with a 254 non-scaled hexagonal pattern were used. For VER analysis, sub-dermal Pt needle electrodes were placed near the visual cortex and stimulated with 8x8 square pattern. Full-field ERG (FF) was measured with corneal electrodes. To demonstrate detection of retinal damage by MFERG over 30 laser spots were placed in opposing quadrants and monitored for 2 wk. In the Brown Norway rat AMD model, choroidal neovascularization was stimulated by applying 8 radial laser photocoagulation spots at a constant distance from the optic disk. In this AMD model, some rats were treated with 1.0% OC-10X or vehicle control three times a day for up to 6 wk. Other rats without laser damage were also treated with OC-10X for up to 6 wk to examine for toxic effects on retina and optic nerve. To demonstrate detection of laser damage by FF, laser damage was compared with intravitreal injection of NMDA (40 nM).
Results: :
In the rat AMD model, MFERG identified laser damaged quadrants as areas of retinal dysfunction and was able to differentiate individual laser spot damage corresponding to approximately 5 non-responsive hexagons (NRH). There were no corresponding changes in VER or FF. Results were corroborated with fluorescein angiography and histology. NMDA treatment significantly reduced FF a-wave amplitude to 171±10.4 µV compared to the contralateral untreated eye (241±14.0 µV; p=0.03). Although in the untreated AMD rats, NRH progressed over a 2 wk period from 5 to 8 hexagons with ~20% decrease in N1 and P1 amplitude, this was not the case with OC-10X treatment. In normal rats, treatment with OC-10X for up to 6 wk had no adverse effect on FF a-, b-wave, oscillatory potential, or flicker response (amplitude or latency) or VER (P1, N1 and P2).
Conclusions: :
In an AMD model, electroretinography can quantify the extent of damage to retina or optic nerve. By this measure sustained topical application of OC-10X was not toxic to either retina or optic nerve. In addition, OC-10X appeared to retard retinal damage.
Keywords: age-related macular degeneration • electroretinography: non-clinical • laser