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E Margalit, JD Weiland, R Clatterbuck, GY Fujii, M Maia, G Torres, SA D'anna, DV Piyathaisere, M Tameesh, MS Humayun; Visual and Electrical Evoked Response (VER, EER) Recorded From Subdural or Epidural Electrodes Implanted Above the Visual Cortex in Normal Dogs Under Two Methods of Anesthesia . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4487.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To compare electrical or visual elicited cortical responses in normal dogs implanted with subdural or epidural electrodes with two methods of anesthesia. Methods:Mixed bread dogs (5 eyes, 1-2 years old) were used in this study. Under general anesthesia (Halothane 2-3 %), a chronic subdural electrode array or several acute epidural electrodes (Ad-Tech, Racine WI) were implanted over the visual cortex. The location of the array was confirmed by X-ray after the operation and 8 weeks later. Experiments began 1 week after the operation. Methods of anesthesia induction used were either Halothane 2.5-3.0% or Propofol 2-3 mg/kg/Fentanyl 5-7 mg/kg. The dog was then intubated and ventilation was controlled. Both methods included the usage of a muscle relaxant Pancuronium 0.1 mg/kg. Anesthesia was maintained with either Halothane 1-1.5 % or propofol 100-150 mg/kg/min/Fentanyl 2-3 mg/kg. Bright flash stimuli for visual evoked responses (VER) were given by a white LED stimulator (Mayo Co. Nagoya, Japan). Electrical stimulus was applied with either a Burian-Allen contact lens or an intraocular probe. All experiments were performed under the guidelines of Johns Hopkins University for animal experimentation. Results:Electrically or visually elicited cortical responses were similar under the two methods of anesthesia used. The mean VER and EER (Burian-Allen) amplitude and latency (for 1ms 4mA stimulus) recorded under Halothane were 34mV/ 58ms and 30mV/ 45ms respectively. The mean VER and EER recorded under Propofol/Fentanyl were 32mV/ 55ms and 28mV/ 47ms respectively. The EER from intraocular stimulation with 2 mA of current had comparable amplitudes and latencies to extraocular stimulation. Conclusion:Subdural electrodes can effectively record VER and EER under general anesthesia. VER and EER have similar amplitudes and latencies when using both methods of general anesthesia. Subdural recording of EER is a sensitive method and may serve as a measuring tool to the efficacy and safety of an intraocular epiretinal prosthesis.
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