Abstract
Abstract: :
Purpose: To ascertain if systematic differences exist in Edinger-Westphal (EW) stimulated accommodative responses in rhesus monkeys anesthetized with propofol versus sodium pentobarbital intravenous anesthesia. It is of interest to use constant perfusion rather than bolus anesthetic delivery to maintain a stable level of anesthesia. Propofol is an anesthetic agent commonly used with constant perfusion in rhesus monkeys. No prior studies have tested if propofol anesthesia produces any undesirable changes in EW stimulated accommodative responses. This study was conducted to compare static and dynamic accommodative responses under the two anesthetic agents. Methods: EW stimulation was used to elicit accommodative responses of increasing amplitudes in both eyes of three young rhesus monkeys. Static accommodative stimulus response functions were recorded with a Hartinger coincidence refractometer. Dynamic refractive changes were recorded using infrared photorefraction, and subsequently, at the same stimulus amplitudes, dynamic biometric changes in lens thickness were recorded using continuous, high resolution A-scan ultrasonography. Experiments were conducted first under pentobarbital delivered as an initial bolus (15 mg/kg) with hourly supplements (10 mg/kg) and one week later under propofol delivered as initial bolus (1.5 mg/kg) and constant perfusion (0.5 mg/kg/min). Static and dynamic accommodative responses as well accommodative peak velocity vs amplitude relationships were compared in each eye between the two anesthetic agents. Results: Maximum accommodative amplitude was not statistically different between the two agents (pentobarbital: 12.42±2.35D; propofol: 11.82±1.67D; t = 0.51, p = 0.63). Maximum accommodative change in lens thickness was also not different (pentobarbital: 0.702±0.11mm/D; propofol: 0.723±0.112 mm/D; t = -0.332, p = 0.75). Characteristics of the dynamic accommodative responses did not change. Peak velocity of change in lens thickness vs accommodative amplitude relationships were similar for the two agents (pentobarbital slope: 2.26±0.31; propofol slope: 2.36±0.64; t = -0.26, p = 0.8). Conclusions: No systematic difference was observed in static or dynamic refractive and biometric accommodative responses between sodium pentobarbital and propofol anesthesia. Therefore future studies of centrally stimulated accommodation using propofol anesthesia can be compared with prior studies under sodium pentobarbital. This study shows that constant perfusion with propofol is an acceptable anesthetic agent for centrally stimulated accommodative experiments in rhesus monkeys.
Keywords: accommodation • animal model • refraction