title: Effects of dorzolamide-timolol and brimonidine-timolol on retinal vascular autoregulation and ocular perfusion pressure in primary open angle glaucoma.
abstract: OBJECTIVE
  To assess whether dorzolamide 2%-timolol 0.5% (D/T) and/or brimonidine 0.2%-timolol 0.5% (B/T) alters retinal vascular autoregulation (RVA) and seated ocular perfusion pressure (sOPP) in primary open angle glaucoma (POAG) patients who demonstrate retinal vascular dysregulation (RVD) on timolol 0.5% alone.
  
  
  METHODS
  In this prospective, observer-masked, crossover study, 21 POAG patients with untreated intraocular pressure (IOP) >21 mmHg were treated for 6 weeks with timolol 0.5%. Subsequently, we measured inferior temporal retinal artery blood flow in the left eye with subjects seated and then while reclined for 30 min using the Canon Laser Blood Flowmeter. Subjects with a change in retinal blood flow in response to posture change outside of the range previously found in healthy subjects were designated as having RVD and randomized to either D/T or B/T for 6 weeks and re-tested. This was followed by treatment with the opposite medication.
  
  
  RESULTS
  Seven of the 21 subjects demonstrated RVD in response to posture change following timolol 0.5%. Multiple linear regression analysis indicated that lower sOPP was the main determinant of RVD (P=0.033). After treatment with D/T, all 7 converted from RVD to normal RVA status (P=0.001). Four of 6 subjects showed a similar return to normal RVA following B/T (P=0.066). Mid-morning sOPP was 41.1±5.5 mmHg post-timolol, 46.3±6.5 mmHg post-D/T, and 38.6±6.0 mmHg post-B/T (D/T vs. B/T, P=0.026).
  
  
  CONCLUSIONS
  D/T significantly improved RVA in POAG patients exhibiting RVD while on timolol 0.5% alone. D/T also increased sOPP compared to B/T. There was no significant difference (P=0.37) between D/T and B/T in improving RVA.
authors.affiliation: Massachusetts Eye & Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Gilbert T
authors.initials: GT
authors.lastname: Feke
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Rhee
authors.forename: Angela V
authors.initials: AV
authors.lastname: Turalba
authors.forename: Louis R
authors.initials: LR
authors.lastname: Pasquale
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000959:Antihypertensive Agents / Q000494:pharmacology; D000068438:Brimonidine Tartrate; D018592:Cross-Over Studies; D004338:Drug Combinations; D005123:Eye / Q000098:blood supply / Q000187:drug effects; D005260:Female; D005902:Glaucoma, Open-Angle / Q000188:drug therapy* / Q000473:pathology; D006706:Homeostasis / Q000187:drug effects*; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011810:Quinoxalines / Q000494:pharmacology*; D012039:Regional Blood Flow / Q000187:drug effects*; D013449:Sulfonamides / Q000494:pharmacology*; D013876:Thiophenes / Q000494:pharmacology*; D013999:Timolol / Q000494:pharmacology*
chemical_list: D000959:Antihypertensive Agents; D004338:Drug Combinations; D011810:Quinoxalines; D013449:Sulfonamides; D013876:Thiophenes; C479140:dorzolamide-timolol combination; D000068438:Brimonidine Tartrate; D013999:Timolol