title: A comparative study on the effects of apraclonidine and timolol on the ophthalmic blood flow velocity waveforms.
abstract: OBJECTIVE
  To evaluate the effects of topical timolol and apraclonidine on retrobulbar blood flow velocity waveforms in a group of healthy volunteers.
  
  
  METHODS
  Apraclonidine 1% and timolol maleate 0.5% single dose administrations were crossed over double masked in 12 healthy volunteers. The intraocular pressure measurements were followed by Doppler examination of the ophthalmic artery and the central retinal artery.
  
  
  RESULTS
  Intraocular pressure was reduced significantly on both treated and fellow eyes after timolol (p = 0.003, p = 0.04 respectively) and after apraclonidine (p = 0.002, p = 0.01 respectively). After apraclonidine administration end diastolic velocity, mean velocity decreased and pulsatility index increased in the ophthalmic artery of both treated and fellow eyes. Resistivity index increased and peak systolic velocity decreased only in the ophthalmic artery of treated eyes. All Doppler indices remained nonsignificant for central retinal artery of both eyes. After timolol administration there were no significant changes of the Doppler indices in the ophthalmic artery and central retinal artery of the treated and fellow eyes.
  
  
  CONCLUSIONS
  Topical timolol and apraclonidine significantly reduced the intraocular pressure. Single dose administration of apraclonidine 1% increased the vascular impedance distal to the ophthalmic artery. On the other hand, timolol 0.5% had no effect on vascular impedance.
authors.affiliation: Department of Ophthalmology, Adnan Menderes University, Aydin, Turkey. orucs@hotmail.com
authors.forename: S
authors.initials: S
authors.lastname: Oruç
authors.forename: E C
authors.initials: EC
authors.lastname: Sener
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D003000:Clonidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D009880:Ophthalmic Artery / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology*; D009883:Ophthalmic Solutions; D011446:Prospective Studies; D012016:Reference Values; D012161:Retinal Artery / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology*; D013999:Timolol / Q000008:administration & dosage / Q000494:pharmacology*; D018608:Ultrasonography, Doppler
chemical_list: D000316:Adrenergic alpha-Agonists; D000319:Adrenergic beta-Antagonists; D009883:Ophthalmic Solutions; D013999:Timolol; C016986:apraclonidine; D003000:Clonidine