title: Dynamic Analysis of Müller's Muscle Response to Phenylephrine.
abstract: OBJECTIVE
  To characterize in vivo response of Muller's muscle to phenylephrine about time and diurnal variation.
  
  
  METHODS
  A nonrandomized trial of adults without (n = 20, 40 eyes) and with ptosis (n = 5, 5 eyes) measured for response of marginal reflex distance-1 (MRD1) to topical phenylephrine (2.5%) every 15 seconds in the morning (6-10 AM) and evening (6-10 PM). Mean MRD1 was plotted over time, and morning and evening MRD1 were compared with the Spearman correlation coefficient (r) and paired t test.
  
  
  RESULTS
  Regardless of the time of day, subjects with and without ptosis had maximal response to phenylephrine within 2 minutes, with persistence of response at 30 minutes. There was good correlation (r = 0.92), with no statistically significant difference in rate or amount of change of MRD1 between morning and evening time points.
  
  
  CONCLUSIONS
  Maximal response to phenylephrine occurs within 2 minutes of instillation with persistence of response at 30 minutes; there appears to be no diurnal variation in phenylephrine testing.
authors.affiliation: University of Texas Southwestern Medical Center, Dallas, Texas, U.S.A.
authors.forename: Sathyadeepak
authors.initials: S
authors.lastname: Ramesh
authors.forename: Ronald
authors.initials: R
authors.lastname: Mancini
mesh_terms: D000293:Adolescent; D058646:Adrenergic alpha-1 Receptor Agonists / Q000008:administration & dosage*; D000328:Adult; D000368:Aged; D001763:Blepharoptosis / Q000503:physiopathology*; D001767:Blinking / Q000502:physiology*; D002940:Circadian Rhythm; D005143:Eyelids / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009130:Muscle, Smooth / Q000187:drug effects* / Q000294:innervation; D010656:Phenylephrine / Q000008:administration & dosage*; D013564:Sympathetic Nervous System / Q000187:drug effects; D013997:Time Factors; D055815:Young Adult
chemical_list: D058646:Adrenergic alpha-1 Receptor Agonists; D010656:Phenylephrine