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Show Journal of Clinical Neuro- ophthalmology 11( 2): 95,1991. Editorial Comment © 1991 Raven Press, Ltd., New York " Pupillary Sparing" Oculomotor Nerve Palsy I'm quite sure that Drs. Blumen, Feiler- Ofryand Korczyn are correct in their observation of a slight weakness of the sphincter in " pupil sparing" third nerve palsies. A similar observation can be made by taking a Polaroid photo in darkness and in light; a small anisocoria appears ( or increases) in light as the affected pupil gets left behind. Since many of these patients have diabetic autonomic neuropathy with patchy denervation of the iris sphincter, this is an uncertain sign at the first exam. There is another problem with making this observation: the original rule of thumb about pupil sparing was constructed at the bedside ( or perhaps from the end of the bed) and from that distance, pupil involvement generally meant a fixed dilated pupil. If a new standard of pupil dysfunction is to be brought in, the whole clinical axiom will have to be revalidated. Nevertheless, I applaud the authors' efforts to make careful observations of pupillary function in a clinical setting. Perhaps they can persuade the 95 authors of the next prospective study of pupil sparing third nerve palsies to examine the pupil in more detail, looking for severity and duration of diabetes; sector palsies of the iris sphincter to light and to near; light- near dissociation; size of pupil in darkness; anisocoria in darkness; anisocoria in bright light; anisocoria at near; pupil cycle time; relative afferent pupillary defect ( RAPD)- and then repeat all of these after the oculomotor palsy has recovered. If all of these observations were made, it might be possible to subtract out the diabetic neuropathy and make a clear statement about pupil involvement during " pupil sparing" third nerve palsy. This might, conceivably, be the basis for a new clinical rule of thumb, but I don't think pupil- cycle time alone is going to do it. H. Stanley Thompson, M. D. The University of Iowa Hospitals and Clinics Iowa City, Iowa |