Effects of common anesthetics on eye movement and electroretinogram

Abstract

High-resolution magnetic resonance imaging (MRI) provides non-invasive images of retinal anatomy, physiology and function with depth-resolved laminar resolution. Eye movement and drift, however, could limit high spatial resolution imaging, and anesthetics that minimize eye movement could significantly attenuate retinal function. The aim of this study was to determine the optimal anesthetic preparations to minimize eye movement and maximize visual-evoked retinal response in rats. Eye movements were examined by imaging of the cornea with a charge-coupled device (CCD) camera under isoflurane, urethane, ketamine/xylazine, and propofol anesthesia at typical dosages in rats. Combination of the paralytic pancuronium bromide with isoflurane or ketamine/xylazine anesthesia was also examined for the eye movement studies. Visual-evoked retinal responses were evaluated using full-field electroretinography (ERG) under isoflurane, ketamine/xylazine, urethane, and ketamine/xylazine + pancuronium anesthesia in rats. The degree of eye movement was ranked as follows (from large to small displacement per unit time): i) 1% isoflurane, ii) 2% isoflurane, iii) propofol, iv) ketamine/xylazine, v) urethane, vi) ketamine/xylazine + pancuronium and vii)1% isoflurane + pancuronium. The ketamine/xylazine groups showed larger dark-adapted ERG a- and b-waves than other anesthetics tested. The isoflurane group showed the shortest b-wave implicit times. Photopic ERGs in the ketamine/xylazine groups showed the largest b-waves with the isoflurane group showing slightly shorter implicit times at the higher flash intensities. Oscillatory potentials revealed an early peak in the isoflurane group compared to ketamine/xylazine and urethane groups. Pancuronium did not affect the a- and b-wave, but did increase oscillatory potential amplitudes. Compared to the other anesthetics tested here, ketamine/xylazine + pancuronium was the best combination to minimize eye movement and maximize retinal function. These findings should set the stage for further development and application of high-resolution functional imaging techniques, such as MRI, to study retinal anatomy, physiology and function in anesthetized rats.

Assessment of Visual and Chromatic Functions in a Rodent Model of Retinal Degeneration

“…These results, although not conclusive, are in agreement with the filter characteristics. Using more animals to study each filter, evaluating the possible influence of the anesthesia, 28 and choosing filters with a more suitable transmittance curve could allow a more detailed analysis.…”

“…The ketamine/xylazine anesthetic shows robust ERGs with large a-wave and b-wave amplitudes, and low eye movements. 28 Pupils were dilated by applying a topical drop of 1% tropicamide (Colircusí Tropicamida; Alcon, Barcelona, Spain). A topical drop of 2% Methocel (OmniVision, Puchheim, Germany) was instilled in each eye before situating the corneal electrode.…”

Normal Clinical Electroretinography Parameters of Healthy Pharaoh Hounddogs

“…Median, minimum, maximum, lower limit of reference interval, upper limit of reference interval, 90% CI for lower limit and 90% CI for upper limit are given. her flash intensity stimulations (Nair et al, 2011), but other investigators reported that volatile anesthetics generally had no noticeable effect on the ERG results (Ekesten, 2007). showed that a combination of xylazine and ketamine has the lowest impact on implicit times and amplitudes without ventral rotation of the eyeball and miosis.…”

“…The determination of normal ERG values is of great importance for clinical practice, considering that there are numerous intrinsic and extrinsic factors influencing the ERG recordings including the age and breeds of the animal (Itoh et al, 2010), the environment and body temperature (Mizota and Adachi-Usami, 2002), pupil diameter, intraocular pressure and eye movement (Marmor et al, 2009;Grozdanic et al, 2010;Nair et al, 2011), electrode type and position (Mentzer et al, 2005), stage of retinal dark adaptation (Maehara et al, 2015), anesthesia technique (Norman et al, 2008;Lin et al, 2009). All of that contribute to interfere with the values obtained from ERG recording; therefore, the investigations aiming to establish a normal range still continue.…”

Laser speckle contrast imaging of blood flow in rat retinas using an endoscope

“…Adult male Sprague-Dawley rats (∼300 g, N ¼ 3) were anesthetized with 1% isoflurane, paralyzed with 3.5 mg∕kg pancuronium bromide to prevent eye motion, 18 and mechanically ventilated. End-tidal CO 2 , heart rate, and oxygen saturation were monitored continuously and maintained within normal physiological ranges.…”