title: Phenylephrine 5% added to tropicamide 0.5% eye drops does not influence retinal oxygen saturation values or retinal vessel diameter in glaucoma patients.
abstract: OBJECTIVE
  To test whether adding topical phenylephrine 5% to tropicamide 0.5% eye drops in the protocol for pupil dilation affects the retinal vessel oximeter measurements in patients with glaucoma. To test whether phenylephrine 5% has an influence as a vasoconstrictor on the retinal vessel width and can improve the proportion of high-quality retinal images in patients with glaucoma.
  
  
  METHODS
  Retinal images of 66 patients with chronic open-angle glaucoma were obtained before and after the administration of phenylephrine 5% eye drops to patients already dilated with tropicamide 0.5% with the Oxymap Retinal Oximeter (Oxymap ehf, Reykjavik, Iceland). Specialized software, Oxymap Analyzer, analysed the images and measured the oxygen saturation and vessel diameter. Oxygen saturation was measured in first- and second-degree vessels. A Mann-Whitney U-test was used to compare both groups. Quality of the images was assessed, and a Fisher's exact test was used to compare the proportion of high- and poor-quality images.
  
  
  RESULTS
  There was no significant difference in arterial and venous oxygen saturation in patients with glaucoma whether dilated by tropicamide alone or a combination of tropicamide and phenylephrine (97 ± 6% versus 96 ± 5%, p = 0.88 for arterial saturation and 66 ± 6% versus 67 ± 6%, p = 0.78 for venous saturation, n = 27). There was no significant difference in vessel diameter between both conditions for the different vessels (p = 0.61 for arterial saturation and p = 0.51 for venous saturation, n = 27). The proportion of high-quality images was significantly higher after the combination regimen compared with tropicamide only (p = 0.0001).
  
  
  CONCLUSIONS
  The addition of topical phenylephrine 5% after tropicamide 0.5% improved the proportion of high-quality retinal oximetry images without influencing the retinal oxygen saturation values or the retinal vessel diameter in patients with glaucoma.
authors.affiliation: Laboratory of Ophthalmology, KU Leuven, Leuven, BelgiumDepartment of Ophthalmology, University Hospitals Leuven, Leuven, BelgiumDepartment of Ophthalmology, Centro Hospitalar de Lisboa Central, Lisbon, PortugalDepartment of Ophthalmology, University of Iceland, Reykjavik, Iceland.
authors.forename: Evelien
authors.initials: E
authors.lastname: Vandewalle
authors.forename: Luis
authors.initials: L
authors.lastname: Abegão Pinto
authors.forename: Olof Birna
authors.initials: OB
authors.lastname: Olafsdottir
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Stalmans
mesh_terms: D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D002908:Chronic Disease; D004338:Drug Combinations; D005260:Female; D005902:Glaucoma, Open-Angle / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D009184:Mydriatics / Q000008:administration & dosage*; D009883:Ophthalmic Solutions; D010092:Oximetry; D010100:Oxygen / Q000097:blood*; D010656:Phenylephrine / Q000008:administration & dosage*; D011446:Prospective Studies; D011680:Pupil / Q000187:drug effects*; D012171:Retinal Vessels / Q000502:physiology*; D014331:Tropicamide / Q000008:administration & dosage*
chemical_list: D004338:Drug Combinations; D009184:Mydriatics; D009883:Ophthalmic Solutions; D010656:Phenylephrine; D014331:Tropicamide; D010100:Oxygen