To the Editor.
—We were most interested to read the article by Blair et al1 in the March issue of the Archives regarding the impressive results obtained by vitreous cavity perfusion in eyes with severe experimental ischemia.It is noteworthy that three eyes in their comparison group (control eyes subjected to 75 to 240 minutes of ischemia generated by intraocular pressures of 170 mm Hg) "appeared to be fairly normal." They attribute this unexpected absence of ischemic damage to variable amounts of glucose remaining in the vitreous cavity fluid of eyes that had previously undergone vitrectomy.An alternate explanation occurred to us. We noted that all animals were anesthetized with ketamine hydrochloride, given as an initial bolus (22 mg/kg) followed by a continuous infusion of 0.33 mg/kg per minute. Ketamine crosses the blood-brain barrier freely and is presumed therefore to cross the blood-retinal barrier well. It is noteworthy that
Bird AC, Lavin MJ. Ketamine and Retinal Ischemia. Arch Ophthalmol. 1989;107(10):1419–1420. doi:10.1001/archopht.1989.01070020493006
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